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The effect of fat in simplified diets on the reproductive organs of the female albino rat during gestation.

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Interest has recently been stimulated by the low-fat studies
of Burr and Burr, and Evans and Lepkovsky, on the relationship betweeii f a t cleficienc-y and disturbances in reproduction.
The present investigation was undertalien to study in ctctail
the effect of fat-poor diets upon the reproductive organs of
the femdc alhino rut during gestation. T wish to tlianlr Dr.
Jenniiigs C. Litzenberg, Dr. c‘. 31. Jackson, Die. Georgc 0.
Burr and Dr. W. R. Bi-owii for their invaluable advice and
criticism during the course of this investigation.
Eighty-seven female albino rats (Mus norvegicus albinus)
of the ~ ~ i n n e s o t a - T ~ ~strain
i s t a r were used in the experiments.
The females m e ~ ebred from stock animals reared on McCollnm’s diet no. 1, and were placed o n diet 551-B (Brown and
Burr. ’36) at tvenning. The weaning weight averaged 44 gm.
Diet 551-I5 consists of :
84.1% siicrose (eommercinl)
12.n<& crude casein
3.9% salt mixture (McCollum’s no. 185).
Accepted in partial fulfillment of the requirements f o r the degree of doctor of
philosophy at TJniversity of Minnesota.
TRB A N . ~ T O ~ I I C %
mLr n m , T - m . 7 0 , NO. 1 A N D s r m r , m r x N i ’ NO. 1
I n addition, each animal was individually fed 0.65 gm. of ether
extracted d r y yeast, 14 y of British Drng House ‘A,’ riosterol
equal to 2 drops of high grade cod live^* oil, and the nonsaponifiable matter from 36 mp. of wheat germ oil. The rats
were weighed ~~-eelcly
undcr carefully standardized conditions.
A t regular inter\-& following maturity, orulation cycles were
determined in order to rlassify the oestrous beliavior of each
TVhe~ibrcediiig was desired, the females at the pro-oesttrons
stage Twre placed in the cage o i a tested male and allowcd to
remain over night. Tlie first day of pregnancy was coiisiderecl
as tlie clay following that on mhich the vaginal plug o r sprrmatozoa were observed. l’ositiw pregnancy was diagnosed
by the appearance of ‘red blood-cell sign’ from the tliirteenth
to fifteenth day following insemination. Daily weights were
recorded during gestation in order to detect resorbing pregnancies.
After R definite plateau in weight liacl been rcaclied the
animals were clirided into two groups. The first group of
forty-one animals was Bcpt on a low-fat diet ; the second g r o ~ i p
of sixteen animals ~ v a sfed a supplement of fresh lard daily.
These were then used laicr as the ‘cared’ controls. A third
group of stock control aiiimwls (Minnesota-T;C’istar strain)
wits used a s a comparative staiiclavd for the ‘cured’ control
animals. ,4 f o u r t h small group of ‘ciired’ control animals
was later furnished from the l o w f a t experiments of Brown
and Burr. These aniinals diffcrccl from tlie second group in
that the protein lcrel was 24%) crude casein and the lard dose
10 instead of 20 drops.
Animals from these groups were Idled on successive days
of pregiiancy from the seventh to the twenty-second day. In
tlic Iosvfat group, d i e r e prolonyed gestation was observed,
aiiiitials were sacrificed daily, up to and including the twentpsixth day.
The preparation o i material f o r microscopic cxarnina1’1011
consisted in the removal of tlie ovaries and the embryos o r
resoi*ption I)odies with a corresponding segment of tlw uterus.
These were fixed in Bouin ’ s solution, cleared aiid dehydrated
in diosan solution and embcddcd in paraffin by the usual
methods. The early specimens were sectioned and mounted
seriaIlJ-; in the larger. ones, every tenth section was mounted.
Hcmatosyliii and eosin were used to stain all sections.
T’lie cliiiical appearances a d characteristics of such fatpoor aiiimals conformed closely willi thosc of Burr and
Brown, whose animals were reared on the same diet in an
adjacent coloiiy room, The rats used in this investigation
sho-\wclfat deficiency symptoms o n l y t o a moderate degree.
Tlie scaliness of tlie feet was not serere and the tail lesions
were not the most marked. A t autopsy marked renal lesions
were not routinely found, and although the mesenteric fat v a s
absent o r very scant, the omcntal fat, as a rule, was abundant.
No indication of xerophthalmia occiirred. The animals on
tlie low-fat diet were not hyperactive and, although weighing
only $OFl as much as their controls, consumed about. the same
amount of food. It was found that the fat-poor animals consumed daily over two times tlie amount of water averaged by
the controls. According t o Burr and Burr (’30) thc excess
water consumption is cvaporalcd from the lungs and skin.
The animals placed on a low-fat diet at weaning did not
show any great retardation of growth during the first 60 days.
As was previously reported by Burr aiid Burr (
and ’30),
the animals were always somewhat subnormal in size and
readied a growth plateau earlier than normal. They started
t o plateau a t about 4 months of age at a weight of approximately 156 to 158 gm. (fig. 1).
After being placed on a cure of 20 drops daily, o r approximately 4% of fresh lard, which contains about 7% of the
essential liiiolic acid, the deficiency s:-mptoms started t o disappear. I n 3 or 4 weeks the scaly condition of the feet cleared
up. Tlie tail lesions disappeared, and there was a marked
clearing of tlie skin. Dandruff disappeared a n d the hair coat
became improved. Renewed growth both in length and weight
(fig. 1) occurred almost immediately.
B u r r and B u r r (’30) observed that orulatiori is often irregular or ceased entirely in fat-free animals (diet 550-B). When
a curative oil is fed, ovulation is resumed. Female rats on
the fat-free diet will mate whcn ovulation occurs. The added
oils so improve the animals as a whole that ovulation is resumed. From the observation of 402 cycles of fifty-seven fat
deficient animals, 80.35c/, were found t o be of 3, 4 and 5 clays
duration. After sixteen animals from the above group had
been on a cure for several weeks, 115 cycles were further
studied, of which 96.53% were of the same duration.
Only three of the ‘cured’ control animals were allowed to
litter. Parturition was normal ; two of the litters were allowed
to lactate and were subsequently successfully weaned.
The control ‘c11red’ and normal stock animals revealed 110
essential difference in the gross nature of the reproductive
organs and their contents.
In the pregnancies that failed to reach term, the abnormal
enlargements were of’ a softer consistency and of a blue color,
in marked contrast to the purple color of normal pregnancy.
The blue discoloration was due to blood in the amniotic cavity.
In the older resorptions the enlargements became more fusiform in shape and assumed a bluish-black color. When
opened, they revealed only dark blood stained debris. Frequently copious hemorrhage into the lumen of the uterine
horns was observed. The decidual bodies (Dnval, 1891) at
the inesometrial border were relatively prominent.
The great variation in the size of‘ the uterine pregnancy
sites indicated that the beginning or rate of resorption was
by no nieans uniform. The conditions encountered were
wholly iinpredictahle. Frequeiitly dead and resorbing fetuses
were intei*mingleed with others whose gross appearance was
normal. When all, or a portion of the fetal sites failed to
undergo early resorption, growth of the fetus mas often retarded and fetal death occurred at different periods during
late pregnancy. ISecause in the fat deficient group of animals
no incidence of successful parturition was encountered, it is
believed that the normal sites observed at the different stages
of pregnancy would have eventually succumbed either to resorption in utero or t o late fetal death with or without delivery.
TT’hen resorption did not occur the pregiiancies were frequently prolonged to the twenty-fourth, twenty-fifth and
twenty-sixth days. If the resorption occurred late in pregnancy, or if there was prolongation of gestation, excessive
ainounts of dark brown, tarry-colored exudate with some
necrotic cellular debris was u s u a l l ~observcd in tlie vaginal
smears, resulting in a delay in the reappearance of oestrus
indicating some pathology of placentation. I n a few cases of
early resorption blood was noted prematurely in the vaginal
smears several days prior to the appearance of the red blood
I n the few animals that were delivered after prolonged
gestation some difficulty in parturition with increased bleeding was noted but none of the animals died. I3owever, during
the period of prolong~dgestation, the animals appeared weals,
inactive and listless.
Periods of prolonged gestation usually terminated in the
dclivcry of a variable number of dead and living fetuses. The
litters were usually small and under-sized. The decrease in
the average number of young per litter was due t o a sporadic
resorption of fetal sites during the early stages of pregnancy
and also to an apparent relative failure of implantation.
Growth of the fetuses in utero was quite rarinble. The live
fetuses appeared weak and anemic, usually succurnbiiig a few
hours after delivery.
In the prolongation of' gestation the placentas appearcd
dark and hemorrliagic. They were of soft consistency and
varied in size. The amniotic fluid disappeared, in some instances, being represented only by a fern strands of a stringy,
tarry-colored material. I n some cascs the fetuses were cast
inside with the membrane intact and mitli the degenerating
placenta adherent outside. The fetuses in these cases were
removed with difficulty from the dry amniotic sacs. S o gross
evidence of pus was noted. Hemorrhage and edema, of the
uterine wall were i'reyuentlp observed suggestive of the
' Couvelaire uterus ' seen in human cases of prematnre separation of the placenta.
The ovaries of the lotv-fat animals where resorption and
prolonged gestation occurred showed cliaracteristic gross
clianges. The corpora lutea of pregnancy appeared larger,
paler and became chalky white in color. The ovaries showing
these signs of degeneration weighed relatively more than
those of the controls. No iicw o r extra corpora lutea were
observed in prolonged gestation.
I n some of the fat deficient animals, blood mas observed
early in the uterine lumen, soon aiter implantation had occurred. Free blood in the uterine lumen dnring early stages
of pregnancy has been found by Huber ('15) in uteri possessing- an abnormal endometrium. Evans, Burr and Althausen
('27) noted in pregnant E-free mothers on the eighth day of
pregiancy extravasated blood in and about the free lumen
of the uterus which lies mesometrial to the dccidual cavity in
which the egg is found.
The placenta gave a varied histological picture. Areas of
localized hemorrhage from rupture of the maternal blood
sinuses were commonly observed near the periphery of the
placenta with exudation into the uterine cavity. Distension
and rupture of the vascular sinuses of both the maternal deciclua and fetal tropholnlast were frequently seen, possibly due
to an increased permeability of the vascixlar endothelium.
Edema was often rioted associated with the vascalar congestion arid hemorrhage in both the uterine wall and placenta.
Following this severe hemorrhage and decidual in jury,
areas of necrosis of varying iiitensity were observed, starting
usually at the maternal side of ilie placenta and progressing
toward the fetal surface. The maternal tissues were prim a d ) - in\dved more than the fetal structures. Areas of
focal necrosis were occasionally observed in the decidua near
the region of the trophoblast.
In cases of early resorption no definite evidence of infection mas encountered. However, in the late resorptions and
cases of prolonged. gestation considerable evidence of inflammation, most likely secondary in nature, was observed. These
areas of focal and diffuse exudation were associated with the
process of necrosis. Both of these processes seemed to occur
secondary t o the hemorrhagic lesions. The histological picture \$-as both that of ail acute polymorphonuclear and polyblastic type of inflammation. I n some sections only granulocytes and macropliages in varying proportions were observed,
while in other sections a more low grade type of inflammat'ion
with a predominance of lymphocytes and plasma cells w7as
observed. The leukocytic infiltration mas most common and
intense usually at the junction of the placenta and chorion
forming along with the associated necrosis, a ring around the
periphery of the placenta. I n many instances tlie leukocytic
infiltration extended into tlie uterine wall.
I n animals autopsied hefore the process of resorption had
been initiated, normal anatomical development of both the
placentas and fetuses was obsprved.
Except in cases of early resoi*ption, the yolk sac with its
entodermal villi, allantois, and other fetal structures showed
normal development. I n cases of prolonged gestation, tlic
yolk sac structure could still be readily identified. Hematopoiesis and differentiation of fetal tissues revealed a normal
histological picture. No failure of mesodermal elements was
I n spite of severe placental injury, very little retardation
of fetal development was observed. Marked decidnal and
placental injury in\-ariahly preceded the alteration in the fetal
tissues. The fetal injury consisted of general disintegration
of the tissues due to lack of nutrition subsequent to placental
injury. I n late resorptioris and prolonged gestation, where
the disease was leas acute, late fetal death and general retardation of fetal development was observed.
The intermuscular and mesometrial deciclual reaction of the
decidual body was delayed in the process of resorption, as
compared with the control sections, still being visible a t the
end of pregnancy and in prolonged gestation. It regr
by lympliocytic aiid leukocytic invasion aiid often extrarasation of blood was noted.
a b o u t the same time that abnormal histological finclings
were noted in the placenta and uterus, microscopic changes
in the ovary were first observed. The lnteal cells becanir
coarsely granulatd, clear and vacuolated ; they swmed to
lose their affinity f o r the eosin stain, and developed a foamy
appearance. Vacuolization arid coarse granulation of the
luteal cell do not normally occur until about tlie seventeenth
day of pregnancy. By the end of pregnancy degeneration is
moderately advanced, but many luteal cells retain their normal structure. No new corpora lutea or maturation of the
graafian follicles were noted in the cases of prolonged gestation and late resorptions. Oestrus was considerably delayed
in cases of prolonged gestation and late resorptions. Only in
some instances of early resorptions did ovulation reappear
before the end of the usual gestation period.
Rats used in this investigation and reared 011 diet 551-B
developed typical fat deficiency symptoms. Brown and Burr
(’36) stated that relatively impure diets may be used for the
production of typical fat deficiency symptoms. When crude
casein is substituted €or purified casein, the weight at the
time of plateau is slightly higher and decline and death are
postponed. However, hematuria, scaly feet, and scaly and
necrotic, tails still occur i o almost the same extent.
The process of reproduction was early impaired and was
more resistant to treatment with curative doses of lard, u~hile
ovulation was affected late and returiiecl t o normal a €ew
weeks after the animal received the lacking dietary unsaturated fatty acids. The dosage of the oil fed seemed to affect
also the rate of cure. Two 01 the ‘cured’ animals (Alaeder)
after receiving 20 drops of lard f o r 95 days, had successful
litters, while some of the Brown and Burr ‘cnred’ rats, after
receiving 10 drops of lard daily for over a year, failed t o
reproduce although manifesting external clinical cures. This
plienomena is probably rxplainecl on the basis that pliysiological cures are not as rapid as external o r clinical cures.
Hansen and 131-own (’37) have shown illat animals given small
quantities 01the methyl estcrs of liiiolic acid suficient to affect
clinical cixres were found to have a vcry little change in the
iodine number of the total blood lipids. I n general, once the
physiology of reproduction was definitely iiitcrfered with,
considerable difficulty was encountered in aEecting an internal
cure. In some cases the contlition secmcd irrc~parablc.
Lowfat diets resulted in atrophic clianges in the uterine
mucosa and maternal deciclua, interfering with the nutrition
necessary f o r the satisfactory nidation of the fertilized ovum,
and f o r the successful continuation arid termination of gestation. A definite relative decrease in the number of implantation sites was apparent. These observations suggested some
disorder of implantation, due most likely to a lack of hormonal stimuli, which interfered with uterine nutrition. If the
fatty acids are associated with the ovarian hormones, it is
possible that on a fat deficient diet the syuthesis of ovarian
hormone may be impaired.
When the fetal sites failed t o undergo early resorption,
fetal death occurred a t different times during late pregnancy
often resulting in prolonged gestation due to abnormalities of
placentation wliich were frequently associated with copious
hemorrhage. Variation in the size of tlie placeiita with hemorrhage, tissue necrosis and infection in tlie placenta and iaterine wall WXR often noted. These atero-placental changes are
similar to these noted by Mason ('35) in ritamiii 'A' deficiency and by Ueno ('34) where there was a lack of vitamin B.
In prolonged gestations there was a significant decrease in
the average number of young per litter and a marked variation in the size of the dead and living fetuses delivered o r
observed at autopsy. Death of the fetus during the latcr
stages of pregnancy mas attributed t o a less acute manifestation of the same factors responsible f o r earlier resorption.
However, the small litters were usually uiidersized and the
living young anemic, weak and of impaired vitality. According t o King ('15) it is possible that prolongation of the gestation period for even 1day materially increases the weight of
the young at birth and further adds that individiials in small
litters weigh more at birth than do individuals in large litters.
Prolonged gestation up t o 26 days and difficult parturition
was frequently associated with copious hemorrhage and great
weakness of the mother. These findings agree with those of
Evans and Lepkovsky ('34) and are similar to the observations of Mason ('35) on the prolongation of pregnancy and
the associated phenomena in vitamin A deficiency. KO signs
of xerophthalmia, abnormal vaginal cornification, o r any
other indication of vitamin A deficiency were observed. Similar prolongation of gestation was also rioted by Barry ( '20)
in rats coming to term after underfeeding from the eleventh
day of gestation. However, in view of the large proportion
of deliveries observed by Barry ('20) in rats in wliicli inanition was much more severe than in our fat deficient rats, there
is no reason to believe tliat growth retardation played a significant role in tho reproductive disturbances. On tlie other
hand, Burr and Browii ( ' 3 6 ) report that when fats high in
unsaturated fatty acids are fed, the gestation period tends to
be less than that found f o r normal stock animals. The prolongation of gestation and difficult parturition is apparently
due in part to deereased vitality and death of fetuses during
the late stages of pregiizancy. Another contributing factor is
the general weakness of the mother, associated with decreased
tone of the abdominal musculature. Decreased responsiveness of the uterine musculature due to lack of necessary liormonal aiid mechanical stimulation is ailother important consideration. Furtliermore, toxicity arising from tlie aiitolysis
of the placental aiid fetal tissues must be recognized.
I n the fat-deficient animals, secondary fetal death is best
cxplained on the basis of decreased nutritive supply as a result of hemorrhage aiid tissue injury in the placenta and
uterine wall. In vitamin A deficiency blason ( ' 3 5 ) wriles that
fetal death is also secondary to marked placental injury.
There is no interfercnee primarily with tlie development of
the fetal structures a i d hematopoiesis as in vitamin E deficiency. According t o Eraiis and Burr ( '27) aiid Uriier. ( T l ) ,
lack of vitamin E produces a retardation of clevelopment and
differentiation of the fetal tissue, with no direct involvement
of the maternal tissues.
It was particularly rioted that in some of tlie partially
'cured' control group, which had first been bred before a
physiological cure had becii affected, that ovulation was considerably dclaycd follomiiig the process of late resorption. It
seems that postpartum oestrus is considerably clelaped by tlie
preseiicc o i retained intra-uterine gestational products. Tlicse
same aniinals often showed bloody vagiiial smears due to excessive uterine bleeding for many days following the expected
date of delivery. Newton ( ' 3 5 ) states that the placeuta plays
an essential part in the inhibition oP oestrus during the latter
half of pregnancy and probably also determines the date of
parturition. After delivery of t h e placenta (pseudoparturition) oestrus occurs in 1to 2 days.
Coincidentally with I h e placental change, alterations both
grossly and microscopically were observed in the ovaries. In
the fat deficient rat (luring prcgiiaiiq- the degenerating
ovaries became relatively larger and heavier than those found
under normal pregnancy conditions. In cases of late pregnancy resorptions and prolonged gestation, the ovaries appeared pale, prominent and chalky. Evans and J q k o v s k y
('34) noted that the ovaries of fat deficient rats in cases of
prolonged gestation very frequently had an unnatural white,
chalky appearance. lllasoii ( ' 3 5 ) found in rats autopsied after
prolonged gestations that the ovaries usually contained very
pale and prominent corpora lutea. Microscopically, these
large chalky corpora lutea rerealed degenerative changes in
the luted cells which hecome clear and vacnoliaed, presenting
a foamy appearance. Some of the cells besides losing their
affinity for the eosin stain, become coarsely granulated. This
histo-pathological picture corrcsponds to that observed hy
Kasper ('31) in vitamin F: deficient rats.
Mason ('35) removed the oraries of vitamin A deficient rats
between the eighteenth and twenty-first clays of pregnancJaiid failed to demonstrate any lessening of the abnormalities
of late gestation in tlie olwratecl rats, thus ruling out hyperfunction of the corpora lutea as the cause of prolonged gestation. Prolongation of gestation and abnormalities of parturition have been observed by Snyder ( '34) in rabbits in which
an adclitional set of corpora liitea was induced by iiijcction of
extracts of pregnancy urine (Aiituitrin S) near term. A normal number of corpora lutca was oljserved in the low-fat
animals hotli grossly and microscopically. The ova and developing graafian follicles revealed no histo-patholog?.
Thew degenerative changes both in the ovaries and placenta appear to occur concomitantly, apparently resulting
from the same etiologic basis, probahly due to a lack of proper
ovarian hormone synthesis and improper endocrine balance.
From extensive experimentation with rats, Selye, Collip and
Thomson ( '35) conclude that the placenta furnishes the necessary stimuliis f o r the maintenance of the corpus luteurn of
pregnancy and determines the length of prcgiiancy either by
its effect on the corpus lutenrn or by its own progestin production, or which is more likely, by both of these means. They
further found that in the rat ovariectomy during pregnancy
does not interfere with the life of the placenta. It terminates
pregnancy only because it causes the death of the fetus probably due t o partial involution of the uterus which considerably
increases the pressure in the gestation sac. The life span of
the placenta was not markedly influenced by the removal of
the embryo. The length of the gestation period must be determined hy factors inherent in the placenta.
The decidual body appeared more prominent both grossly
and microscopically in the pregnant fat deficient animals.
TJrner ( '29) noted the same findings in the failed pregnancies
of vitamin F: deficient animals.
As a practical aspect of the study it might be well to point
out at iliis time that as Burr arid Burr ('30) suggest, the
human diet is often exceedingly low in fats of any kind and
that when fats are added they usually contain little of the
acids more unsaturated than oleic. It is possible that our high
carbohydrate and protein diets, carrying very little of the
unsaturated oils, a r e contributory factors to poor health and
sterility. The addition of egg yolk and cod liver oil to diets
may often improve the patient because of the fatty acid rather
than the vitamin content. F o r example, cures of anemia with
cod liver oil have been reported and it has been sliotvn that
there is a relation between experimented anemia aiid uiisaturated fatty acids of the blood plasma. The preralence of dry
skin and abiiormal kidneys may be directly attributed t o improper fat intake. As the liver is apparently limited in its
ability to produce these acids, they should be plentifully supplied through the diets.
1. Animals reared on diet no. 551-B sliowed the typical
characteristics of tlie f a t deficiency syndrome.
2. Reproductive function is early impaired on a f a t clcficient
diet. The findings substantiated tlie observations of Burr and
Brown, that reproduction was n o t normal until some time
after a clinical cure had been obtained.
3. Ovulation is impaired late on a fat-poor regimen, but
responds early t o curative doses of uiisaturated fatty acids.
4. A definite relative failure of implantation was observed,
due t o atrophic changes and undevelopment of thc uterine
miieosa and maternal decidua.
5. Resorptions o r prolonged gestation resulted from fat
deficient diets. No successfiil gestations were obtained with
fat deficient animals.
6. His tologically, rariable degrees of hemorrhage, necrosis
and secondary inflammatory csuclate were observed in the
placenta and uterine wall.
'7. In fat deficiency, fetal death was secondary to marlred
placental injury.
8. Early interruption of gestation frecjuentlp occurred if
the fat dcficiency symptoms TIYW very acute.
9. I n less acute fat cleficimcy, prolonqed qcstation occurred.
10. Prolonged gestations n'ere frequently associated with
excessive uterine bleeding, difficult partnritioii and great weakness of the mother.
11. T,essenecl vitality or death of fetuses, decreased tone of
tlie abdoniinal and uterine musculature, and possihle lack of
the necessary hormonal stimulation, were reo.ardecl as the
important etiologic faetors of p r o l o n g d gestation.
12. Degenerative changes in the ovaries of fat deficient animals occnrred conconiitaritly with the ntero-placental pathology, The large chalky ovaries, commonly observed, microscopically showed vacnolization and coarse granulation.
13. The decidual bodies arc prominent i n prolonged gestation and late resorption.
14. The failure of reproduction in linmaiis due to lack of
adequate fat in the diet is considered possible.
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E R&I.
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albina, effect, simplifing, diet, gestational, female, fat, rat, organy, reproduction
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