Hippocampal volume and the course of depressive symptoms over eight years of follow-up

OBJECTIVE

To estimate the association between hippocampal and total brain volume and the course of depressive symptoms over eight years of follow-up in patients with a history of vascular disease.

METHOD

Within the SMART-Medea study, 636 participants (62 ± 10 years) had a 1.5-tesla brain MRI obtaining hippocampal and total brain volumes. Depressive symptoms were assessed with the Patient Health Questionnaire-9 biannually during eight-year follow-up. Generalized estimating equation models with robust standard errors were used to assess the associations of hippocampal and total brain volumes with depressive symptoms during follow-up adjusting for age, sex, education, and intracranial volume. An interaction term between volume and time (6-month intervals) was included to examine whether the course of depressive symptoms differed according to hippocampal and total brain volume.

RESULTS

The mean PHQ-9 score was 2.8 ± 3.5. Smaller hippocampal volumes were associated with an increasing course of depressive symptom levels, while larger volumes were associated with decreasing levels (P-value interaction = 0.07). Smaller total brain volume was associated with consistently higher levels of depressive symptoms, but not with change in course of depressive symptoms (P-value interaction = 0.45).

CONCLUSION

Smaller hippocampal volume but not total brain volume is associated with poorer course of depressive symptoms over eight years of follow-up.

Childhood maltreatment modifies the relationship of depression with hippocampal volume

BACKGROUND

Childhood maltreatment (CM) may modify the relationship between major depressive disorder (MDD) and hippocampal volume reduction. To disentangle the impact of MDD and CM on hippocampal volume we investigated the association between MDD and hippocampal volume in persons with and without a history of CM in two independent cohorts.

METHOD

We used data of 262 participants from the Netherlands Study of Depression and Anxiety (NESDA) (mean age 37 years, 32% male) and 636 participants from the SMART-Medea study (mean age 61 years, 81% male). In both studies a 12-month diagnosis of MDD and CM were assessed using a diagnostic interview. Hippocampal volume was measured in NESDA using FreeSurfer software on 3-T magnetic resonance (MR) images and in SMART it was manually outlined on 1.5-T MR images. With analysis of covariance adjusted for intracranial volume, age, gender and lifestyle factors we estimated the effects of MDD and CM on hippocampal volume.

RESULTS

In both cohorts CM was not significantly associated with hippocampal volume. After pooling the data MDD was associated with smaller hippocampal volume (B = -138.90 mm(3), p = 0.05) and the interaction between MDD and CM reached significance (p = 0.04); in participants with CM, MDD was related to smaller hippocampal volume (NESDA: B = -316.8 mm(3), p = 0.02; SMART: B = -407.6, p = 0.046), but not in participants without CM (p > 0.05).

CONCLUSIONS

Our study shows that in two independent cohorts, particularly in individuals with CM, a diagnosis of MDD is related to smaller hippocampal volume. Prospective studies are needed to further determine through which mechanism CM may amplify the relationship between MDD and hippocampal volume.

The influence of negative life events on hippocampal and amygdala volumes in old age: a life-course perspective

BACKGROUND

Psychosocial stress has been related to changes in the nervous system, with both adaptive and maladaptive consequences. The aim of this study was to examine the relationship of negative events experienced throughout the entire lifespan and hippocampal and amygdala volumes in older adults.

METHOD

In 466 non-demented old adults (age range 60-96 years, 58% female), hippocampal and amygdala volumes were segmented using Freesurfer. Negative life events and the age at which these events occurred were assessed by means of a structured questionnaire. Using generalized linear models, hippocampal and amygdala volumes were estimated with life events as independent variables. The statistical analyses were adjusted for age, gender, intracranial volume, lifestyle factors, cardiovascular risk factors, depressive symptoms, and cognitive functioning.

RESULTS

Total number of negative life events and of late-life events, but not of early-life, early-adulthood, or middle-adulthood events, was related to larger amygdala volume. There were interactions of early-life events with age and gender. Participants who reported two or more early-life events had significantly smaller amygdala and hippocampal volumes with increasing age. Furthermore, smaller hippocampal volume was found in men who reported two or more early-life events, but not in women.

CONCLUSIONS

These results suggest that the effect of negative life events on the brain depends on the time when the events occurred, with the strongest effects observed during the critical time periods of early and late life.

High amounts of broccoli in pasta-like products: nutritional evaluation and sensory acceptability

Pasta and noodles were enriched with concentrations of broccoli powder (BP) up to 30% (v/v). To ensure the benefits from the broccoli nutrients, their leakage during cooking should be prevented. Such leakage is determined by the microstructure. In a previous study we have shown that the microstructure can change dramatically in such broccoli-enriched products. In this article we investigated the amount of nutrients retained within the product. As a representative of nutrients we have chosen glucosinolates (GLs). Therefore, we have investigated the concentration of these phytochemicals in dried and cooked pasta and noodles. We have found that glucosinolates present in the pasta and noodles increase linearly with the volume fraction of BP up to 20%. At 30% BP the retained amount of GLs was equal to that of 20% BP and did not increase further. Therefore incorporation of 30% BP does not lead to additional health benefits over incorporation of 20% BP. We conclude that the nutritional function of our pasta-like products can be improved by enrichment up to 20% broccoli. This value is much higher than that found in common commercial products (which is a few percent). In this article we also briefly address the sensory acceptability of such products. Up to 20% broccoli the products turned out to remain acceptable. Combining this with our results on texture analysis we conclude that the GLs release, sensory acceptability and textural properties are related via the microstructure.

Interactive effect of reduced pollen availability and Varroa destructor infestation limits growth and protein content of young honey bees

Varroa destructor in combination with one or more stressors, such as low food availability or chemical exposure, is considered to be one of the main causes for honey bee colony losses. We examined the interactive effect of pollen availability on the protein content and body weight of young bees that emerged with and without V. destructor infestation. With reduced pollen availability, and the coherent reduced nutritional protein, we expected that V. destructor infestation during the pupal stage would have a larger negative effect on bee development than without infestation. Moreover, when raised with ample pollen available after emergence, infested pupae were expected not to be able to compensate for early losses due to V. destructor. We found that both V. destructor infestation and reduced pollen availability reduced body weight, abdominal protein level, and increased the head to abdomen protein ratio. The availability of pollen did indeed not result in compensation for reduced mass and protein content caused by V. destructor infestation in young bees after 1 week of their adult life. Both V. destructor and nutrition are top concerns for those studying honey bee health and this study demonstrates that both have substantial effects on young bees and that ample available pollen cannot compensate for reduced mass and protein content caused by V. destructor parasitism.

A new high intensity and short-pulse molecular beam valve

In this paper, we report on the design and performance of a new home-built pulsed gas valve, which we refer to as the Nijmegen Pulsed Valve (NPV). The main output characteristics include a short pulse width (as short as 20 μs) combined with operating rates up to 30 Hz. The operation principle of the NPV is based on the Lorentz force created by a pulsed current passing through an aluminum strip located within a magnetic field, which opens the nozzle periodically. The amplitude of displacement of the opening mechanism is sufficient to allow the use of nozzles with up to 1.0 mm diameter. To investigate the performance of the valve, several characterizations were performed with different experimental methods. First, a fast ionization gauge was used to measure the beam intensity of the free jet emanating from the NPV. We compare free jets from the NPV with those from several other pulsed valves in current use in our laboratory. Results showed that a high intensity and short pulse-length beam could be generated by the new valve. Second, the NPV was tested in combination with a skimmer, where resonance enhanced multiphoton ionization combined with velocity map imaging was used to show that the NPV was able to produce a pulsed molecular beam with short pulse duration (~20 μs using 0.1% NO/He at 6 bars) and low rotational temperature (~1 K using 0.5% NO/Ar at 6 bars). Third, a novel two-point pump-probe method was employed which we label double delay scan. This method allows a full kinematic characterization of the molecular beam, including accurate speed ratios at different temporal positions. It was found that the speed ratio was maximum (S = 50 using 0.1% NO/He at 3 bars) at the peak position of the molecular beam and decreased when it was on the leading or falling edge.

BDNF Val66Met genotype modulates the effect of childhood adversity on subgenual anterior cingulate cortex volume in healthy subjects

According to the neurotrophic hypothesis of depression, stress can lead to brain atrophy by modifying brain-derived neurotrophic factor (BDNF) levels. Given that BDNF secretion is affected by a common polymorphism (rs6265, Val66Met), which also is associated with depression, we investigated whether this polymorphism modifies the effect of childhood adversity (CA) on local gray matter (GM) volume in depression-relevant brain regions, using data from two large cohorts of healthy subjects. We included 568 healthy volunteers (aged 18-50 years, 63% female) in our study, for whom complete data were available, with magnetic resonance imaging data at 1.5 Tesla (N=275) or 3 Tesla (N=293). We used a whole brain optimized voxel-based morphometry (VBM) approach assessing genotype-dependent GM differences, with focus on the amygdala, hippocampus and medial prefrontal cortex (PFC; including anterior cingulate cortex (ACC) and orbitomedial PFC). CA was assessed using a validated questionnaire. In both cohorts, we found that BDNF methionine (Met)-allele carriers with a history of CA had significantly less GM in subgenual ACC (P<0.05) compared with Met-allele carriers without CA and Val/Val homozygotes with CA. No differences were found in hippocampus, amygdala and orbitomedial PFC. On the basis of our findings, we conclude that BDNF Met-allele carriers are particularly sensitive to CA. Given the key role of the subgenual ACC in emotion regulation, this finding provides an important mechanistic link between stress and BDNF on one hand and mood impairments on the other hand.

Amygdala to hippocampal volume ratio is associated with negative memory bias in healthy subjects

BACKGROUND

Negative memory bias is thought to be one of the main cognitive risk and maintenance factors for depression, but its neural substrates are largely unknown. Here, we studied whether memory bias is related to amygdala and hippocampal volume, two structures that are critical for emotional memory processes and that show consistent volume alterations in depression.

METHOD

Structural magnetic resonance imaging (MRI) was carried out in 272 healthy participants (62% female, 18-50 years old). All images were acquired on 1.5 T Siemens MRI scanners. Automatic segmentation of amygdala and hippocampus was performed using the FIRST module of FSL. Negative memory bias was assessed by the self-referent encoding/evaluation test.

RESULTS

Negative memory bias was associated with larger amygdala (p=0.042) and smaller hippocampal (p=0.029) volumes. In additional analyses, we found that, compared with the associations found with hippocampus and amygdala volume separately, a stronger association was found between negative memory bias and the ratio of amygdala:hippocampus volume (p=0.021).

CONCLUSIONS

In non-depressed subjects we found that larger amygdala and smaller hippocampal volumes are associated with negative memory bias. This suggests that an increased amygdala:hippocampus volume ratio plays a role in cognitive vulnerability often seen in individuals with high risk for depression and that these structural brain differences may pre-date the onset of depression.

Early and late life events and salivary cortisol in older persons

BACKGROUND

It has been hypothesized that stressful life events are associated with changes in hypothalamic-pituitary-adrenal (HPA) axis regulation, which increases susceptibility to psychiatric disorders. We investigated the association of early and late life events with HPA axis regulation in older persons.

METHOD

Within the Longitudinal Aging Study Amsterdam (LASA) 1055 participants (47% male), aged 63-93 years, collected saliva within 30 min after waking and late in the evening. Early and late life events were assessed during a home interview. The associations between life events and cortisol levels were examined using linear regression and analysis of covariance with adjustments for demographics, cardiovascular risk factors and depressive symptoms.

RESULTS

Within our sample, the median morning and evening cortisol levels were 15.0 nmol/l [interdecile range (10-90%): 7.4-27.0 nmol/l] and 2.8 nmol/l (10-90%: 1.5-6.3 nmol/l), respectively. Persons who reported early life events showed lower levels of natural log-transformed morning cortisol [B=-0.10, 95% confidence interval (CI) -0.17 to -0.04] and flattened diurnal variability of cortisol (B=-1.06, 95% CI -2.05 to -0.08). Those reporting two or more late life events showed higher levels of natural log-transformed morning cortisol (B=0.10, 95% CI 0.02-0.18) and higher diurnal variability (B=1.19, 95% CI 0.05-2.33). No associations were found with evening cortisol.

CONCLUSIONS

The results of this large population-based study of older persons suggest a differential association of early and late life events with HPA axis regulation; early life events were associated with a relative hypo-secretion of morning cortisol and flattened diurnal variability, while late life events were associated with elevated secretion of morning cortisol and high diurnal variability of cortisol.

Polyclonal Antisera To Distinguish Strains and Form Variants of Photorhabdus (Xenorhabdus) luminescens

In this study antisera against Photorhabdus luminescens strains were prepared for the first time. P. luminescens is a bacterial symbiont of entomopathogenic nematodes belonging to the genus Heterorhabditis. To characterize P. luminescens strains and form variants, we produced polyclonal antisera against P. luminescens PE (obtained from nematode strain NLH-E87.3) and against the primary and secondary forms of P. luminescens PSH (obtained from nematode strain DH-SH1). In double-diffusion tests all form variants of strain PE reacted with the antiserum against the primary form, but each variant produced a different diffusion pattern. The primary and secondary forms of strain PSH were also serologically different. Antiserum 9226 reacted with almost all P. luminescens strains tested, but it reacted differently with each strain in the double-diffusion test, showing that the strains were serologically different. The specificity of the antisera was increased by cross-absorption. After cross-absorption the antiserum against the strain PSH primary or secondary form was specific for that form and did not react with the other form. Using the cross-absorbed antisera in immunofluorescence cell-staining tests, we could distinguish primary and secondary form cells in a mixed strain PSH culture.