Professor Bromage directs the Hard Tissue Research Unit (HTRU), a mineralized tissue preparation and imaging technology development laboratory of the Department of Biomaterials and Biomimetics, NYUCD. Mineralized tissue biology with emphasis on its translation to environmental and evolutionary studies are key to many of Bromage's HTRU pursuits, which include microanatomical correlates of bone and tooth biomechanics, enamel and bone growth rate variability in respect to environmental perturbations, and skeletal disease research. Recently, he has reported on a hitherto unrecognized chronobiological rhythm in bone microstructure that corresponds to a previously observed but enigmatic enamel formation rhythm in mammals, establishing the basis for understanding how chronobiology and organismal life history evolution are integrated.
Professor Bromage supplements laboratory research with African Late Pliocene paleontological fieldwork of significance to human evolutionary research, the surveys of which have recovered the oldest known representative of the human genus, Homo rudolfensis, 2.4 Ma, as well as its contemporary, Paranthropus boisei, from the shores of Lake Malawi. Fieldwork on Late Pleistocene pygmy elephant and pygmy hippopotamus localities in the Turkish Republic of Northern Cyprus are also ongoing, which provides a natural experiment of relevance to interpretations of modern human dental reduction.
The integration of graphic and heuristic elements in the digital photomicrography of bone and tooth microanatomy is important to Professor Bromage, who presents the work as abstract art; his exhibit is currently touring Europe. Images include a variety of subjects of relevance to his equally integrative research agenda, from images of gene knockout mice in novel cancer research, to human evolutionary studies including micro-anatomical images from the bones of "Lucy" (a representative of the earliest humans from Ethiopia, ca. 3.0 Ma).
Professor Bromage is recipient of the 2010 Max Planck Prize in the Life Sciences (paleobiomics; emphasis in Human Evolution), is Honorary Professor of La Salle University, Madrid, Spain, and is Honorary Research Fellow of the Department of Paleoanthropology, Senckenberg Research Institute, Frankfurt, Germany. (Source: http://dental.nyu.edu/faculty/ft/tgb3.html)
HUMAN ENAMEL PRISMS
The enamel of modern humans and their ancestors varies in microanatomical structure in ways that are thought to resist the propagation of cracks. To examine this problem it is necessary to image and observe the orientations of units of enamel structure called prisms that course outward from the junction with underlying dentine to the outer surface of the tooth. In this example of modern human enamel deep to the surface of a cut and polished tooth and imaged by backscattered electron imaging in the scanning electron microscope, we see that the prisms have divergent courses. Some prisms are seen to course longitudinally and wander lengthwise in the plane of the image while others course in and out of the plane of the image and appear semicircular. This heterogeneity provides crack propagating resistance to a tooth, enabling it to withstand the mechanical forces of chewing. Some early hominins with large robust teeth have more anti-crack propagating heterogeneous enamel than other species. Color was imparted to the image by an image analysis program for measuring prism orientation (original size 180 μm).
ATAPUERCA CAVE ATTACK 1
Image of bone microanatomy by portable confocal scanning optical microscopy. A novel portable Nipkow disk-based confocal microscope was employed in the imaging of bone from human and bear skeletons discovered from fossil bearing deposits at Atapuerca, Spain, approximately 0.4-0.7 m.y old.Bones from Atapuerca have been severely affected by bacterial attack during fossilization, eliminating much of the internal microanatomy, but leaving the external macroanatomy in perfect condition.
In order to visualize any remaining microanatomy it is necessary to use the autofluorescence potential of bone. Thus, instead of using normal white light, the microscope is configured to image the fluorescence of bone when using ultraviolet light. The image obtained here is a 3D image of bacterial attack, the colors depicting damage at various levels from top (blue) to bottom (red). The colors are very mixed up because of the degree and nature of the attack (original size 700 μm).
ATAPUERCA CAVE ATTACK 2
This is an image of tooth root (dentine) microanatomy by portable confocal scanning optical microscopy. A novel portable Nipkow disk-based confocal microscope was employed in the imaging of cave bear bone from from fossil bearing deposits at Atapuerca, Spain, approximately 0.4-0.7 m.y old.Some bones from Atapuerca have been severely affected by bacterial attack during fossilization, eliminating much of the internal microanatomy, but leaving the external macroanatomy in perfect condition. In this case the bacterial attack occurs in “plaques” of damage, roughly circular areas of damage.Specimens courtesy of the Departamento de Paleontología de la Universidad Complutense de Madrid (original size 700 μm).
This exciting image shows bone from the femur (thigh) of an Emu, a large flightless bird from Australia. The image was acquired by incident optical microscopy of a rough cut block surface of the bone. The image has been color coded according to depth in the bone. Dark blue-to-black illustrates a deep plexus of vascular canals, coursing more or less from left to right, that run circumferentially around the bone. Light blue striae represent near-surface marks left by the sawing of the bone and yellow striae are such marks at the very top surface of the bone block (original size 1750 μm).
EARLY HOMO ENAMEL
This is an image of enamel macro- and microanatomy by portable confocal scanning optical microscopy. A novel portable Nipkow disk-based confocal microscope was employed in the imaging of an early human tooth discovered from fossil bearing deposits on the eastern shore of Lake Turkana, Kenya. Enamel surface macro-anatomy is characterized by vertical bands representing near 7-day increments of enamel deposition, called perikymata, while subsurface microanatomical details of enamel prisms are visible as a regular arrangement of small circular spots. Color is imparted to the grey-level image based on reflection intensities (Specimen courtesy of the National Museums of Kenya, Nairobi, Kenya Field width 0.6 mm).
The image shows bone microanatomy by portable confocal scanning optical microscopy. A novel portable Nipkow disk-based confocal microscope was employed in the imaging of femoral bone from the famous “Lucy” discovered from fossil bearing deposits at Hadar, Ethiopia, approximately 3.0 m.y old. This image provides information about the degree of orientation of the cell spaces beneath the surface of the bone, which in turn can tell us about the way in which the bone was growing during childhood. Well oriented cells means that the surface was depositing bone during growth, while randomly oriented cells means that the surface was resorbing bone during growth; bone deposition, coupled with bone resorption, is how bones grow. Comparing the organization of bone cells between Lucy, belonging to the species Australopithecus afarensis, with other species of early human, can help us to understand changes in how bones grew over human evolutionary time. Imaging courtesy of the Ethiopia National, Addis Ababa, Ethiopia (original size 110 μm).
3D BONE STRUCTURE
Here you can see 3D images of a blood vessel contained within layers of bone called lamellae. Using specialized software, various color schemes were applied to color lamellae depending upon the orientation of their collagen, and areas of surrounding lamellae (bottom and left) were rendered transparent to enable a look at internal features. Each lamella in human bone takes about 8 (males) or 9 (females) days to form.
The rings, called circuli, of a fish scale represent increments of growth; their departure from uniform widths between rings is an indication of variation in growth rate. Thus waters that are polluted, too warm, or too cold, affect the growth rate of the fish and its scales. We notice that the rings of fish living near to the Chernobyl nuclear power plant following the April 26, 1986 disaster are of a different character than those living far away.
Scale from fish living in a lake distant from the Chernobyl nuclear power plant in Russia.
Scale from fish living in lake near to the Chernobyl nuclear power plant in Russia.
CUTMARK COLOR RELIEF
This is an image from a bone “plaque” from the Grotte du Taï, France, ca. 10,000 BC, which records a continuous serpentine sequence of sets and subsets of daily engraved marks for a period of more than three years.
The depth characteristics are rendered as a color-coded map. From deepest to highest, the colors grade from dark blue, through greens at intermediate heights, and yellows, reds, and brown at highest points on the tool.
FISH IN SPACE
The image shows a scale of a Zebra fish (Xiphophorus helleri
) flown aboard the NASA Space Shuttle. Fish scales grow from the small inner ring outward, the number of rings corresponding to the age of the fish. Measurements of widths between rings help to describe how the fish reacts to zero gravity. Preliminary studies indicate that growth rate is little perturbed, establishing the future possibility of developing aquaculture in space.
HUMAN ENAMAL CRACK
This is an image of a human molar enamel that was mechanically tested to generate a crack. The image was acquired by incident optical microscopy of the crack, which had been stained with colored inks to reveal its propagation through the enamel. In this instance, a major crack, colored yellow, separated the enamel around the boundaries of enamel formed by adjacent enamel forming cells. Here, these boundaries are represented as an undulating upper and lower border to the yellow crack.
HUMAN FEMUR FIGURE MARS & VENUS
Here you can see a collage of polarized light montages of human thighbones. These images, from the middle of the thighbone of thirty males and females through the adult age range, represent colorized versions of circularly polarized light images, highlighting regions of collagen fibers of differing orientation. Areas assigned warm colors (yellows, pinks and reds) represent collagen fiber orientations resistant to compressive forces during life. Areas assigned to cool colors (dark blues, light blues and greens) represent collagen fiber orientations resistant to tensile forces.
We use these color maps to document between-individual variation in walking and way of life, about which you can see there is considerable variability. Individuals in their twenties are at the base of the Venus and Mars figures. The tip of the male figure is comprised of individuals in their eighties, while the top of the female group comprises women from their mid-fifties to seventies, equivalent in age to the men’s stem of the arrow.
Specimens courtesy of Dr. John G. Clement, University of Melbourne School of Dental Science and the Victorian Institute of Forensic Medicine, Australia.
To determine the strength of a material, such as this human dentine from a molar tooth, a diamond point is applied to the surface with a known force. The resulting indent diameter is related to how deep the diamond is able to penetrate the surface with that force. This method, therefore, measures density, which is of interest to many disciplines, including health science and materials science. We find it also interesting that this mark provides a record of an event and, as such, reflects the “culture” of science.
This image shows a bone microanatomy by portable confocal scanning optical microscopy. A novel portable Nipkow disk-based confocal microscope was employed in the imaging of femoral bone from the famous “Lucy” discovered from fossil bearing deposits at Hadar, Ethiopia, approximately 3.0 m.y old. This image provides information about the degree of orientation of the collagen fibers within the bone, which in turn can tell us about the ability of the tissue to resist different kinds of mechanical stresses encountered in everyday life; green is collagen perpendicular with the plane of the screen, and light blue represents collagen parallel with the screen. Comparing the organization of bone tissue between Lucy, belonging to the species Australopithecus afarensis
, with other species of early human, can help us to understand more about how bone structure and function has varied over human evolutionary time.
Imaging courtesy of the Ethiopia National, Addis Ababa, Ethiopia
ON THE CUSP
The cusp of a human molar tooth is a wonderfully complex structure. While the mechanisms remain obscure, we can observe the behavior of enamel forming cells by the tooth material they lay down during development. In this histological thin section, the “hill” below, is the dentine of the tooth. From the surface of the dentine, enamel developed upward in swirling patterns that have some relevance to the biomechanical resistance of the tooth to chewing forces. The junction between enamel and dentine is called the enamel-dentine junction, or EDJ. At tooth cusp tips this swirling phenomenon renders a tissue called “gnarled enamel” for its appearance. Other characteristics observed in this image are “enamel tufts”, which are enamel deficient defects arising from the EDJ upward into enamel, which here are like flames on the surface of dentine. Color in this image arises from the employ of circularly polarized light imaging by a conventional compound light microscope. Typically, apart from their general growth trajectory away from the EDJ at cusp tips, because the enamel cells regularly swirl into and out of the plane of section, the enamel is formed in patterns that, when mineralized, reveal crystal orientations that appear in orange when in the plane of the section, or blue when passing up and down through the section.
Fractured enamel surface of an early hominin Paranthropus robustus molar from Swartkrans, South Africa, ca 1.5-2.0 m.y. Imaging deep to the surface reveals incremental enamel microanatomy; striae seen from upper left to lower right, across which course the enamel prisms.. Overlain on this image is a color relief map of the actual 3D topography of this surface; superficial orange and blue to green regions somewhat deeper. Specimen courtesy of the Transvaal Museu, Pretoria, South Africa.
RAT IN SPACE SERIES
Forelimb bone of a growing rat (Rattus rattus) flown aboard the NASA Space Shuttle.
RAT IN SPACE BINARY
RAT IN SPACE FLUORESCENCE
A 100-micron thick section from the femur (thighbone) of Vombatus ursinus
, a wombat. Wombats are members of Marsupiala, the highly diverse group of mammals that includes pouched animals such as the kangaroo, koalas, opossums, and many other species. Native to Australia, wombats are powerful, robustly built, dog-sized diggers. The thickness of the bone seen here is a good indication of the strength of a wombat. The colors in this image represent differences in the orientation of collagen fibers present in the bone, as viewed in circularly polarized light. Despite their close evolutionary relationships to one another, marsupials are expected to show a diversity of collagen fiber patterns, depending on the way that they move during life and the resulting forces to which their bones are subjected.
The upper molar root dentine of a southern African zebra (Equus burchelli) is observed by backscattered electron imaging in the scanning electron microscope. The image derives from the polished cut surface of a tooth sectioned through its center. The image is called a “density-dependent” image; black represents holes (i.e. no dentine), blue is least densely mineralized (i.e. relatively less hard dentine), and yellow is most densely mineralized (i.e. relatively more hard dentine). Each hole actually represents a tube associated with one long dentine cell process in life. The number of holes and the proportion of yellow to blue may characterize certain species and relate to their feeding habits.
This research concerns interests in the skeletal and conservation biology of African mammals. Ongoing efforts include the collection of animal skeletons immediately upon death (of natural causes) from National parks in South Africa, Zambia, Malawi, Tanzania, and Kenya.