Tailoring beams to overcome attenuation allows light-sheet microscopy to image at greater depth with enhanced contrast.

We have investigated the effect of Airy illumination on the image quality and depth penetration of digitally scanned light-sheet microscopy in turbid neural tissue. We used Fourier analysis of images acquired using Gaussian and Airy light-sheets to assess their respective image quality versus penetration into the tissue. We observed a three-fold average improvement in image quality at 50 μm depth with the Airy light-sheet. We also used optical clearing to tune the scattering properties of the tissue and found that the improvement when using an Airy light-sheet is greater in the presence of stronger sample-induced aberrations. Finally, we used homogeneous resolution probes in these tissues to quantify absolute depth penetration in cleared samples with each beam type. The Airy light-sheet method extended depth penetration by 30% compared to a Gaussian light-sheet.

Background/Aims: The medial amygdala (MeA) responds to olfactory stimuli and alters reproductive physiology. However, the neuronal circuit that relays signals from the MeA to the reproductive axis remains poorly defined. This study aimed to test whether MeA kisspeptin (MeA^Kiss) neurons in male mice are sensitive to sexually relevant olfactory stimuli and transmit signals to alter reproductive physiology. We also investigated whether MeA^Kiss neurons have the capacity to elaborate glutamate and GABA neurotransmitters and potentially contribute to reproductive axis regulation. Methods: Using female urine as a pheromone stimulus, MeA^Kiss neuronal activity was analysed and serum luteinizing hormone (LH) was measured in male mice. Next, using a chemogenetic approach, MeA^Kiss neurons were bi-directionally modulated to measure the effect on serum LH and evaluate the activation of the preoptic area. Lastly, using in situ hybridization, we identified the proportion of MeA^Kiss neurons that express markers for GABAergic (Vgat) and glutamatergic (Vglut2) neurotransmission. Results: Male mice exposed to female urine showed a two-fold increase in the number of c-Fos-positive MeA^Kiss neurons concomitant with raised LH. Chemogenetic activation of MeA^Kiss neurons significantly increased LH in the absence of urine exposure, whereas inhibition of MeA^Kiss neurons did not alter LH. In situ hybridization revealed that MeA^Kiss neurons are a mixed neuronal population in which 71% express Vgat mRNA, 29% express Vglut2 mRNA, and 6% express both. Conclusions: Our results uncover, for the first time, that MeA^Kiss neurons process sexually relevant olfactory signals to influence reproductive hormone levels in male mice, likely through a complex interplay of neuropeptide and neurotransmitter signalling.

Light-sheet microscopy (LSM) has received great interest for fluorescent imaging applications in biomedicine as it facilitates three-dimensional visualisation of large sample volumes with high spatiotemporal resolution whilst minimising irradiation of, and photo-damage to the specimen. Despite these advantages, LSM can only visualise superficial layers of turbid tissues, such as mammalian neural tissue. Propagation-invariant light modes have played a key role in the development of high-resolution LSM techniques as they overcome the natural divergence of a Gaussian beam, enabling uniform and thin light-sheets over large distances. Most notably, Bessel and Airy beam-based light-sheet imaging modalities have been demonstrated. In the single-photon excitation regime and in lightly scattering specimens, Airy-LSM has given competitive performance with advanced Bessel-LSM techniques. Airy and Bessel beams share the property of self-healing, the ability of the beam to regenerate its transverse beam profile after propagation around an obstacle. Bessel-LSM techniques have been shown to increase the penetration-depth of the illumination into turbid specimens but this effect has been understudied in biologically relevant tissues, particularly for Airy beams. It is expected that Airy-LSM will give a similar enhancement over Gaussian-LSM. In this paper, we report on the comparison of Airy-LSM and Gaussian-LSM imaging modalities within cleared and non-cleared mouse brain tissue. In particular, we examine image quality versus tissue depth by quantitative spatial Fourier analysis of neural structures in virally transduced fluorescent tissue sections, showing a threefold enhancement at 50 µm depth into non-cleared tissue with Airy-LSM. Complimentary analysis is performed by resolution measurements in bead-injected tissue sections.

Introduction: Advances in human immunodeficiency virus (HIV) treatment have led to greater survival rates and have brought about a shift in the burden of disease from mortality to morbidity. The main purpose of this study is to estimate the Disability Adjusted Life Years (DALYs) of HIV infected patients associated with different modes of transmission. Methods: Non-parametric Kaplan-Meier estimate has been utilised to develop survival function, and the mean residual life model has been utilised to estimate the life expectancy of patients alive at the end of the study. The impact of factors such as age, sex, hepatitis B and syphilis on life expectancy has also been assessed by fitting a proportional mean residual life model. DALYs have been calculated based on the results of both models. Results: Retrospective time to event data of HIV patients undergoing Antiretroviral Therapy (ART) in Dr Ram Manohar Lohia Hospital, New Delhi, India has been utilised to illustrate the modelling technique. The study suggests that in total, 42300.15 DALYs were lost which includes 39765.10 years of life lost due to premature death and 2535.05 years of life lived with disability. When the covariates were taken into consideration, 47592.14 DALYs were found to have been lost with an average of 17.64 DALYs lost per patient. Conclusion: Our results suggest that the high-risk groups such as homosexuals and parent to child transmission are a major cause of concern, which are in accordance with the existing national policies. Also, we would suggest that gender-based and age-based policies should be incorporated to reduce the burden of disease.