close

Вход

Забыли?

вход по аккаунту

?

The blood supply of the areas of langerhans a comparative study from the pancreas of vertebrates. (Preliminary paper.)

код для вставкиСкачать
.4UTHOR'S ABSTRkCT OF THIS P A P E R I S S U E D
B Y T HE BIRLIOGRAPHIC SERVICE, h l 4 R C H
17
THE BLOOD SUPPLY OF THE AREAS OF LANGERHANS,
A COMPARATIVE STUDY FROM THE PANCREAS OF
VERTEBRATES. (PRELIMINARY PAPER.)
h/IARY DRUSILLA FLATHER
Bryn Mawr College
EIGHT FIGURES
INTRODTJCTION
Since 1895, when the islets of Langerhans were declared by L.
A. Shaeffer to be endocrinous glands, secreting a substance capable of modifying the metabolism of carbohydrates in the tissues,
the study of these organs has been provocative of deep interest
and much controversy. It is my purpose in this paper to present
a purely comparative study of the specialized blood supply in the
islets. Therefore, in my consideration of the work already
accomplished in the general field, I shall mention only those facts
which are necessary for an adequate comprehension of my problem. A detailed summary of the literature up to 1906 is given by
Laguesse in La Revue Generale d'Histologie, vol. 2, 1906-1908.
Two important contributions since then are the papers of Lydia
M. Dewitt in The Journal of Experimental Medicine, 1906, vol.
8, and of R. R. Bensley in The American Journal of Anatomy,
1911-1912, vol. 12.
It is generally conceded that islets are groups of internally
secreting glands embedded in the pancreatic tissue of all species
of vertebrates. Their origin is still a matter of controversy,
although the careful work of Dewitt and of Bensley seems to
prove conclusively that the islets and acini arise from common
anlagen, later becoming differentiated and incapable of transformation one into the other. The cells, varying in form and
structure, are always arranged in cords or masses separated by
71
72
MARY DRUSILLA FLATHER
large anastomosing blood-vessels. The nature of this vascular
network is analogous to that found in other endocrinous glands,
especially the thyroid and suprarenals. According to Jordan
and Ferguson, certain arterial branches enter the islets and form
a plexus of large capillaries from which the blood is drained
through the venous system. Dewitt, however, claims that the
sinusoids communicate intimately with an interacinar capillary
plexus and with larger vessels of venous origin only, basing her
theory upon her inability to find near the islets any of the characteristic arterial endothelium.
The islets vary in size and shape according to their vascular
content and according to whether they are singular or compound.
Harris and Gotv find three distinct types of islets-those which are
lymphoid in appearance with many small, deeply stained nuclei
in a syncytial mass of tissue; those having distinct cell outlines,
and those consisting of compound cell groups divided into
smaller areas by strands of connective tissue. It is probable
that the first two types represent physiological differentiation
only. Usually the cells toward the periphery of the islet are
massed, while those in the center are arranged in irregular cords
one or two cells in depth resting directly on the walls of the
capillaries. As a rule, a connective-tissue sheath surrounds the
islet, sometimes penetrating within, and frequently failing to
separate the acinous and islet cells completely. It is often difficult to distinguish the islet from the peri-insular zone, but in
general the islet cells may be recognized by their polymorphism,
their slight colorability, their small size, and the large chromatin
content of their nuclei. I n addition to the rich blood supply
there is also in the islet a plexus of nerve fibers, which was shown
by Pensa to pass along the blood-vessels and in between the cells.
TECHNIQUE
I n my own investigations on the histology of the islet cells I
am much indebted to Dr. Frederick M. Allen for supplying me
with the greater part of the material which I have used. The
specimens of alligator, opossum, horse, coon, badger, and skunk
BLOOD SUPPLY AREAS O F LANGERHANS
73
pancreas which I obtained from him had been fixed in either
chrome sublimate or Zenker’s solution and embedded in paraffin.
From these blocks I cut sections 3 to 5 p thick, and stained them
all in Mallory’s connective-tissue stain before mounting them
for observation. Fresh material was taken from a guinea-pig
and a rabbit. Following Bensley’s directions, I employed all
four of his methods of fixation, and used the neutral gentian
stain. The most successful results were from the Zenker bichromate sublimate fixation. Both neutral gentian and Mallory’s
connective-tissue stain proved excellent in the differentiation of
the islets and the surrounding tissue. The drawings were made
with a camera lucida, using a Zeiss oil-immersion lens and no. 4
ocular, resulting in a total magnification of 1250.
T H E BLOOD SUPPLY O F THE AREAS O F LANGEBHAKS
A cursory glance at the accompanying figures shows how varied
is the arrangement of the vascular areas in the islets of Langerhans. To a certain extent there may be variation even in the
islets from the same individual, but I shall endeavor to show
that there are certain distinctive features which characterize
islets in the different species of vertebrates.
In the alligator, figure 1, the islets are noticeably large, compound, and syncytial in appearance, with a very appreciable
granular content due to great physiological activity. This latter
feature may be due merely to the youth of the specimen. With
the physiological vascular injection produced by congestion it is
easy to see how the distended blood-vessels surround the area,
rarely penetrating within it, except in the connective-tissue
sheaths, and forming almost a complete barrier between the islet
and acinous cells. There is no differentiationbetween the peripheral cells and those of the interior of the islet,, and no indication of a capillary network. In ten islets from the same
individual there was no appreciable variation except in size.
Many of the islets were larger than the one represented here.
The islet from the opossum, figure 2, presents a quite different
appearence with distinct cell divisions, a sinusoidal arrangement
T i i l .4B&TOMICXL RECORD, VOL.
16, NO. 2
74
MARY DRUSILLA FLSTHER
of blood-vessels in the interior of the area, no encircling vessels,
arid no definite capsule or sheath to separate the islet from the
acinous cells. A peculiarity of the cell arrangement not found
in any other pancreas observed is the radial grouping around
capillaries, which is most suggestive of the radial form of acinous
cells about their lumiiia. These essential features were found
in ten islets from the same pancreas.
The islet from the horse, figure 3, is definitely ovoid in shape,
and is surrounded by a frame of blood-vessels and connective
tissue, which in places penetrate within the area. The cells are
clearly outlined, but show no differentiation between the central
and peripheral grouping in any of the ten islets studied.
The distinctive feature of the raccoon islet, figure 4,is the compound form and lobular appearance. The smaller masses are
separated by a network of blood-vessels and connective tissue
which also lies between the acinous cells and the large islet area.
Another characteristic is the extensive penetration of the lobules
by the capillaries. The cell outlines are fairly distinct, but again
there is no differentiation, even where the blood-vessels have
invaded the central mass. There was no variation worthy of
note in ten islets from the same pancreas.
As might be expected from their close relationship, the skunk
and badger, figures 5 and 6, have islets with many similarities
of structure. In both, the blood-vessels only partially separate
the acinous from the islet cells. There is a definite sinusoidal
network running through the central mass. This makes it possible for nearly every cell to come in contact with the capillaries,
a feature which should greatly facilitate the circulation of the
secretion. Figure 6 shows a large accumulation of interlobular
connective tissue at one side where the area of the islet reaches
the periphery of the lobule. From a study of ten islets from
Fig. 1 Island of Langerlians from young alligator. Aq chrome sublimate
Mallory. X 417.
Fig. 2 Island of Langerhans from opossum. Zenkrr blallory. X 417.
Fig. 3 Islandof Langerhans from horse. hq. chomc sublirnatehIallory. X 417.
Fig. 4 Island of Langerhans from r:xoon Zenker AIallory. X 417.
a, :xcinous cells; b, islet cells; c, blood vessels; d, connective tissue.
BLOOD SUPPLY AREAS O F LANGERHANS
75
76
MA4RP DRUSILL 4 FLATHEK
BLOOD SUPPLY AREAS O F LANGERHANS
77
each individual it was concluded that the islet areas were smaller
in the skunk than in the badger pancreas.
In the islet of the rabbit, figure 7, the line of demarcation
between the islet and acinous cells is difficult to define because the former frequently extend into the acinous area and
there is no circle of blood-vessels or connective-tissue sheath to
mark the division. The blood supply is sinusoidal in nature. In
this form there is a slight indication of cord-liKe cell grouping and
a massing of cells with larger nuclei toward the periphery. Unlike Dewitt, I found in the ten islets examined no radial arrangement similar to that which was observed in the opossum.
The guinea-pig islet, figure 8, shows a fairly regular contour,
a connective-tissue sheath separating the islet and acinous areas,
and an irregular network of insular cells frequently but one cell
in depth surrounding the large and abundant sinusoids. After
careful observation of islets from two individuals and with due
allowance for faulty fixation, I decided that these islet areas.were
the most sponge-like of any that I have examined.
From the islets which I have described I feel that there is an
arrangement of the cells and blood-vessels which may be regarded
as characteristic of a species. Within certain limits there may
be variation in size and in abundance of capillaries with a consequent rearrangement of the islet cells. However, I believe that
the special features can be proved peculiar to the species. I
realize that the proof is inadequate as yet owing to the fact that
wit,h one exception I have studied islets from only one individual
of a species. It is my intention to continue the investigation
with many more species and more individuals of the species. I
am greatly indebted to Dr. David H. Tennent for his helpful
supervision of the work.
Fig. j Island of Langerhans from skunk. Chrome sublimate Mallory.
417.
Fig. 6 Island of Langerhans from badger. Chrome sublimate Mallory.
X
X
417.
Fig. 7 Island of Langerhans from rabbit. Zenlrer neutral gentian. X 417.
Fig. 8 Island of Langerhans from guinea-pig. Zenker neutral gentian. X
417.
a, acinous cells; b, islet cells; c, blood vessels; d, interlobular connective
tissue.
Resuniido por la autora, Inez Whipple Wilder.
Una anomalia de la circulacih de la porta en el gato.
E n un gat0 macho de gran tamaiio y aproximadamente de
un aiio de edad, un espacioso canal sanguine0 colateral, formado
por la anastomosis de 10s tributarios de la porta con l a vena
fr6nica izquierda, hacia posible el paso direct0 de la sangre desde
dichos tributarios a la vena postcava, evitando de este mod0 el
trayecto normal a trav6s del higado, si bien este trayecto estaba
abierto. Con esta anomalia estaban asociados: un aumento de
tamaiio de 10s riiiones y una disposicih irritable en extremo, por
parte del animal.
Translation by Jose F. Nonidez
Columbia University
Документ
Категория
Без категории
Просмотров
1
Размер файла
550 Кб
Теги
paper, stud, area, vertebrate, langerhans, supply, pancreas, comparative, blood, preliminary
1/--страниц
Пожаловаться на содержимое документа