Unbiased and efficient estimation of the total number of terminal bronchiolar duct endings in lung: a modified physical disector

Effect of local, long-term delivery of platelet-derived growth factor (PDGF) on injected fat graft survival in severe combined immunodeficient (SCID) mice

SUMMARY BACKGROUND

Autogenous fat injection is widely used for the correction of acquired and congenital soft tissue defects. However, the high absorption rate results in the need for over-correction of the defect and repeat procedures. We hypothesised that platelet-derived growth factor (PDGF), a potent mitogen and known stimulant for murine preadipocytes, would improve fat graft survival when concentrations were sustained with a gelatine microsphere delivery system.

METHODS

Abdominal fat was harvested from an otherwise healthy 43-year-old woman during a breast reconstruction. Prior to subdermal injection into severe combined immunodeficient (SCID) mice, the fat grafts were divided into 1-ml aliquots, mixed with microspheres bound to PDGF, free PDGF, or nothing depending on its experimental group, and weighed. The following experimental groups were thus created (minimum n=8 per group): (1) fat graft control, (2) fat graft with free PDGF, (3) fat graft with blank microspheres, and (4) fat graft with microspheres bound to PDGF. After 12 weeks, the fat xenografts were harvested for analysis of weight maintenance and histological and morphometric evaluation.

RESULTS

The addition of PDGF bound to gelatine microspheres was effective in improving xenograft weight maintenance (P=0.018) and preservation of adipose tissue architecture (P<0.0005) compared to controls at 3 months. The microspheres were completely absorbed at 12 weeks.

CONCLUSIONS

Sustained, local delivery of PDGF via a gelatine microsphere delivery system resulted in improved weight maintenance of the xenografts with greater preservation of adipose tissue architecture at 3 months compared to controls.

Evidence for the disproportionate mapping of olfactory airspace onto the main olfactory bulb of the hamster

Olfactory receptor neurons (ORNs) project to the rodent main olfactory bulb (MOB) from spatially distinct air channels in the olfactory recesses of the nose. The relatively smooth central channels of the dorsal meatus map onto the dorsal MOB, whereas the highly convoluted peripheral channels of the ethmoid turbinates project to the ventral MOB. Medial and lateral components of each projection stream innervate the medial and lateral MOB, respectively. To ascertain whether such topography entails the disproportionate representation seen in other sensory maps, we used disector-based stereological techniques in hamsters to estimate the number of ORNs associated with each channel in the nose and the number of their targets (glomeruli and mitral and tufted cells) in corresponding divisions of the MOB. Each circumferential half of the MOB (dorsal/ventral, medial/lateral) contained about 50% of the 3,100 glomeruli and about 50% of the 160,000 mitral and tufted cells per bulb. We found equivalent numbers of ORNs with dendritic knobs in the medial and lateral channels (4.5 million each). However, the central channels had only 2 million knobbed ORNs, whereas the peripheral channels had 7 million. Thus, there is a disproportionate mapping of the central-peripheral axis of olfactory airspace onto the dorsal-ventral axis of the MOB, encompassing a greater than threefold variation in the average convergence of ORNs onto MOB secondary neurons. We hypothesize that the disproportionate projections help to optimize chemospecific processing by compensating, with differing sensitivity, for significant variation in the distribution and concentration of odorant molecules along the olfactory air channels during sniffing.

Organogenesis of lung and kidney in Thoroughbreds and ponies

Equine lung and kidney organogenesis has not previously been examined with the use of unbiased stereological techniques. The present study examined healthy (control) pony and Thoroughbred lungs and kidneys to establish baseline data of organ development from before birth until maturity at age 3-18 years. Whole left lungs and kidneys were collected from 45 equine postmortem examinations (34 Thoroughbred, 11 pony). Stereological techniques were used to estimate whole kidney, cortex and medulla volume, total glomerular number and volume-weighted mean glomerular volume, lung volume, total terminal bronchiolar duct ending number and total gas exchange surface area. Lungs were demonstrated to be more developed at birth in ponies compared with Thoroughbreds. Thoroughbreds showed continued lung development after birth, a unique micromorphogenic postnatal development. Kidneys were developed equally in ponies and Thoroughbreds. This study has provided data on the baseline development of the equiune lung and kidney which can be used in further studies to examine whether the development of these organs is affected by specific illnesses.

Terminal bronchiolar duct ending number does not increase post-natally in normal infants

Organ development may be assessed by estimating the total number of functional units within an organ over time; the potential functional capacity of that organ may be represented by the total number of functional units present in the fully developed, mature organ. Relative development of the lung at birth is essential to provide sufficient oxygenation of body tissues and so maintain ex utero life. Estimation of the number of one type of functional unit of the lung - terminal bronchiolar duct endings - provides important information regarding development of the lung. This investigation used stereological techniques, specifically Cavalieri's Principle and the "physical disector", to estimate total number of terminal bronchiolar duct endings in the upper lobe of the right lung of a group of 14 control infants between 0 and 66 weeks post-natal age. Results demonstrate that total terminal bronchiolar duct ending number does not increase significantly over the first 24 weeks of post-natal life in normal infants (P=0.997). The unbiased, design-based techniques used in this paper confirm previous model-based research that indicates that terminal bronchiolar duct ending development is completed before birth.