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THE HORSEMEN OF APOCALYPSE,
A MICROSCOPIC VIEW. PART I
MANUEL del CERRO, USA,
INTRODUCTION
The Apocalypse attributed to John of Patmos (John the Divine), also
called the Book of Revelation, is the last canonical book of the New
Testament in the Christian Bible [1]. Prominent in the narrative are the socalled Horsemen of Apocalypse, mounted knights that run the Earth
disseminating sorrow and death (Figure 1).
Theology is not one of my fields of exploration, but I think I may
have found the microscopic equivalent of Horsemen of Apocalypse and
would like to share that finding with fellow microscopists.
Figure 1. The Horsemen of Apocalypse in an early Renaissance
version. (Woodcut by Albrecht Dürer, 1471–1528)
MICROSCOPIC VIEW
I have recently acquired (2008) a set of slides that show tissues
infected with the microbes of anthrax, leprosy, syphilis, tuberculosis, and an
opportunistic fungal infection in an AIDS patient. These infectious agents
are the microscopic equivalents of the Horsemen that spread dead and
sorrow. Since the subject of infectious disease is of general interest, I will
comment on the slide set, on each of the individual slides, and briefly, on the
corresponding disease.
THE SLIDE SET
These five slides (Figure 2) were sold as a set in Ebay in August 2008.
They are sections of tissues heavily infected with the agents of anthrax,
leprosy, syphilis, tuberculosis, and with pneumocystis carinii. As for
technical information I only have that provided in the label of each slide,
complemented by the examination of the slides under the microscope. The
slides are signed with the initials A. J. D. These initials correspond to the
name of Anthony J. DiDonato. Mr. DiDonato, from Philadelphia, is widely
known as a most prolific microphotographer. These slides attest to his
proficiency as histotechnologist and slide mounter as well. [Discalimer: I
never met Mr. DiDonato and have no monetary interest in his work].
Figure 2. Scanned image of the set of slides.
SLIDE 1. ANTHRAX INFECTION OF THE LUNG.
Anthrax is a disease that has been recently in the news for some very
unfortunate reasons. It was known as a disease of the livestock since the
Classical Antiquity (Virgil, Georgics, 29 BC), and it was not much later that
human infection was also recognized, making of this a zoonotic disease (one
shared by animals and humans). Its causative agent is Bacillus anthracis, a
gram-positive, spore-forming, facultative anaerobic bacteria (one able to live
with little or no oxygen if needed). There are cutaneous, intestinal,
pulmonary, and meningeal forms of the disease [2]. This slide shows the
pulmonary form. Typically, pulmonary anthrax starts with chest pain, low
fever, and dry cough. As the disease advances there are breathing
difficulties, high fever, and low blood-oxygen levels, as evident by bluish
coloration of the skin. In severe cases the patient experiences profound
respiratory distress. Comparison between the lung seen in Figure 3, and that
of a normal lung (Figure 4) explains why.
Figures 3 and 4. Microscopic views of the anthrax-infected lung
(top) and of a normal lung (bottom). Both pictures were taken at the
same magnification and under the same conditions. The empty areas in
both are the respiratory alveoli or air sacs; these receive inhaled air and
allow oxygenation of the circulating blood. The density of those empty
sacs is considerably lower in the anthrax-infected lung; hence, the
respiratory distress experienced by the patient. Occlusion of blood
vessels by heavily infected blood clots compounds the situation (Figures
5 A & B). Field width for pictures 3 & 4 is 420 µm.
[A description of the photographic technique used to obtain these
and all other photomicrographs is given in the Appendix]
Figure 5 A & B. A blood vessel (V) is seen in a panoramic view in
A, and at higher magnification in B. A) The lumen of the vessel is
occluded by a blood clot. The field width is 420 µm. B) The blood clot
and the lung tissue around it are infiltrated by an incredible number of
deeply stained anthrax bacilli (thin, short, darkly stained rods); the fact
that the section is relatively thick emphasizes this fact. The stain is
superb. The field width is 170 µm.
SLIDE 2. LEPROSY LESION OF THE SKIN
Leprosy has been known for millennia. For almost as long, leprosy
has been feared and misunderstood, thought to be a hereditary disease, a
curse, or the expression of divine punishment. The patients were shone from
contact with their communities; they often were segregated into colonies,
sometimes under dismal conditions. It is sad to recognize that all that
unnecessary extra suffering was imposed on the patients for no valid medical
reason - leprosy is minimally contagious!
Clinically, the disease is a chronic, progressive (if untreated)
inflammatory process that affects preferentially the upper respiratory
mucosa, the skin (Figure 6), and the nerves. The nerve lesions, leading to
loss of sensation, are indirectly responsible for the progressive aggravation
of unfelt wounds that may lead to ulcerations or even to loss of fingers.
Leprosy does not express itself with the same intensity or lesion distribution
in all patients; thus a number of classifications were devised trying to
distinguish between the different forms. Recently, the World Health
Organization has replaced a widely used classification that recognized six
forms with a new one that recognizes only two: the pauci-bacillary and the
multi-bacillary. This is based on the presence of few or many bacilli in the
affected tissues.
The causative agent is Mycobacterium leprae, a rod-shaped, aerobic
(oxygen-dependent) bacillus, remarkable in being unable to live freely,
being only able to exist intracellularly. The bacillus was discovered in 1873,
by Dr. Gerhard Hansen of Norway (Figure 7). In recognition of this fact,
leprosy was also called Hansen’s disease [4]. Microscopically, M. leprae is
an extremely difficult organism to stain on account of the waxy coat that
prevents many stains from reaching the body of the bacterium proper. That
difficulty was overcome with the introduction in 1882 of the Ziehl-Neelsen
carbol-fuchsin stain that makes M. leprae appear as a red, acid-fast organism
(Figure 8 A). It would be out of place to describe the staining method in
detail here as such a description can be easily found in texts [3] and
particularly on the web [5], instead I will discuss the microscopic findings
made in the corresponding slide.
Figure 6. An old (ca 1900) picture of a leprosy patient exhibiting
profuse skin lesions.
Figure 7. A late 1800s photograph of Dr. Gerhard Henrik Hansen,
the discoverer of the leprosy agent.
Figure 8 A. A multi-bacillary skin lesion as seen in the leprosy
slide. It shows myriads of Mycobacteria, single or in clusters, stained in
red by the Zielhl-Neelsen method. The V-shaped structure in the top is
part of a tangential section of a hair shaft. The field eight is 170 µm.
Figure 8 B. Panoramic view of the same lesion. The area seen in
figure 8 A, including the section of the hair shaft is located near the
center of the field. The Mycobacteria are concentrated in the dermal
region (dermis) of the skin (see figure 10 for orientation). Contrast in
this picture is low since the stain purposely keeps the tissue lightly
stained in order to emphasize the heavily stained bacilli. The field eight
is 2,100 µm.
Figure 9. A view of the normal skin. A few sections of hair shafts
are present, compare with the field seen in figure 9.
This concludes the overview of the slide set and of two of the disease
represented in it. In the second part of this survey I will continue with the
“apocalyptic” view of the remaining slides. I will discuss, briefly but from a
general perspective, the microscopic correlates of tuberculosis, syphilis, and
of a complication of the AIDS infection. This two-part series will end on a
note of hope, as the book of Apocalypse does.
APPENDIX
All the photomicrographs were taken using a Nikon D80 camera, set
in manual mode and attached to an Olympus BHS microscope. Planapochromat objectives ranging from 4x to 40x were used. In figure 8 A, a
yellow-green filter was used to enhance the red-stained bacilli. Koehler
illumination was used for all pictures. Field size was measured with a 2 mm
long stage micrometer. The images were digitally enhanced using Apple’s
iPhoto program.
REFERENCES
1. The Book of Revelation, or Apocalypse of John. The Jerusalem
Bible (1966). New Testament, pages 430-451. Doubleday & Company, Inc.,
Garden City, New York.
2. A Brief History of Anthrax. The Office of the Public Health Service
Historian.
http://lhncbc.nlm.nih.gov/apdb/phsHistory/resources/anthrax/anthrax.html
3. Luna, Lee G. (1992) Histopathological Methods and Color Atlas of
Special Stains and Tissue Artifacts. American Histolabs, Inc., Gaithersburg,
Maryland, p. 183.
4. History of Leprosy (2008). www.stanford.edu /group/parasites/
ParaSites2005/Leprosy/history.htm
5. Ziehl-Neelsen Stain (2008). www.123expbiology.com/t/01174369005/