QUANTITATIVE STUDIES OF HAIR GROWTH IN THE ALBINO RAT

1958 ◽  
Vol 16 (4) ◽  
pp. 351-359 ◽  
Author(s):  
ELIZABETH JOHNSON
Keyword(s):  
Hair Growth ◽  
Female Rats ◽  
Male Rats ◽  
Hair Length ◽  
Inhibitory Effects ◽  
Albino Rat ◽  
Rate Of Growth ◽  
Quantitative Studies ◽  
Reduced Rate ◽  
Second Wave

SUMMARY 1. Spaying of female rats aged 7 weeks accelerated the passage of the second wave of hair growth. Longer hairs were produced as a result of faster growth, and the rate of loss of dead or 'club' hairs [cf. Johnson, 1958] was increased. 2. Oestradiol implanted into spayed females delayed the initiation and passage of the wave. Shorter hairs were produced by a reduced rate of growth, and loss of club hairs was inhibited. 3. Castration of male rats aged 7 weeks accelerated the passage of the second wave of growth, and implantation of testosterone slowed it down. Testosterone had no effect on the definitive length of hair produced or on the rate at which club hairs were lost. 4. Oestradiol implanted into castrated males produced the same effects as in spayed females except that it had no effect on the time of initiation of the wave. 5. Combined implantation of testosterone with oestradiol into castrated males did not off-set the inhibitory effects of the oestradiol on hair length or rate of loss of club hairs, but may have slightly speeded the hair wave.

QUANTITATIVE STUDIES OF HAIR GROWTH IN THE ALBINO RAT

1958 ◽  
Vol 16 (4) ◽  
pp. 360-368 ◽  
Author(s):  
ELIZABETH JOHNSON
Keyword(s):  
Hair Growth ◽  
Ovarian Hormones ◽  
The Body ◽  
Female Rats ◽  
Inhibitory Effects ◽  
Albino Rat ◽  
Adrenal Hormones ◽  
Quantitative Studies ◽  
Males And Females ◽  
Second Wave

SUMMARY 1. Adrenalectomy 2 weeks before the start of the second wave of hair growth advanced the beginning of the wave in female rats, and speeded its passage over the body in both males and females. The rate of loss of club hairs was slightly accelerated, but there was no effect on the definitive length of hair produced. 2. Adrenalectomy after the wave of hair growth had begun was less effective. 3. ACTH did not affect the time at which the wave of hair growth began but delayed its passage. ACTH had no effect on the loss of club hairs nor on the definitive length of hair produced. 4. Implantation of oestradiol retarded the start and rate of passage of the wave, and the loss of club hairs in both spayed and spayed adrenalectomized animals. Oestradiol must therefore have some action which is independent of the adrenals. Nevertheless, inhibitory effects of oestradiol on these aspects of hair growth were enhanced by the presence of the adrenals. The action of oestradiol in reducing the rate of hair growth was, on the other hand, unaffected by the presence or absence of the adrenals. 5. Adrenal hormones delay the passage of the growth wave to a greater extent than ovarian hormones, but they have no effect on the rate of hair growth, and, compared with ovarian hormones, affect the loss of club hairs only slightly. It is therefore suggested that these three main phases of hair growth may be controlled by mechanisms which are at least partially independent.

QUANTITATIVE STUDIES OF HAIR GROWTH IN THE ALBINO RAT

1958 ◽  
Vol 16 (4) ◽  
pp. 337-NP ◽  
Author(s):  
ELIZABETH JOHNSON
Keyword(s):  
Hair Growth ◽  
The Body ◽  
Female Rats ◽  
Albino Rats ◽  
Albino Rat ◽  
Growing Period ◽  
Quantitative Studies ◽  
Rates Of Growth ◽  
Resting Period ◽  
Follicular Activity

SUMMARY 1. The patterns of the first and second hair growth waves, forming the second and third coats, were followed in albino rats which had been dyed black before the start of hair growth. 2. The length of hair produced during the growth waves varies from region to region of the body. These regional differences are partly the result of differences in rates of growth, but mainly due to differences in the duration of the period of follicular activity. 3. The duration of the growing and resting periods varies in different areas of the body. For example, in the ventral region the resting period between the first and second waves lasts for about 14 days and the growing period of the second wave for only 12 days, whereas in the mid-dorsal region the resting period lasts for about 4 weeks and the growing period about 19 days. 4. As the growth wave spreads over each area every follicle produces a new hair alongside the dead or 'club' hair. Loss of club hairs then begins, and the rate of loss varies from region to region of the body. 5. In female rats the growth wave moves more slowly, the definitive length of hair is shorter, and the loss of club hairs is slower than in the male. The sexual differences in hair length are the result of differing rates of growth, and there is no difference in the duration of follicular activity between the sexes. 6. It is suggested that in assessing the effect on hair growth of any treatment the following aspects should be considered: (a) Time of initiation of the growth wave and its duration. (The length of the resting period in any region will depend on both these factors.) (b) Duration of the growing period. (c) Rate of elongation of the hair during the growing period. (d) Rate of loss of club hairs.

Hair Growth and its Relation to Vascular Supply in Rotated Skin Grafts and Transposed Flaps in the Albino Rat

Development ◽  
1959 ◽  
Vol 7 (3) ◽  
pp. 417-430
Author(s):  
F. J. Ebling ◽  
Elizabeth Johnson
Keyword(s):  
Hair Growth ◽  
Vascular Supply ◽  
Albino Rats ◽  
Skin Grafts ◽  
Albino Rat ◽  
Growing Period ◽  
Rate Of Growth ◽  
Second Wave ◽  
Follicular Activity

Hair-Growth in the rat occurs in a series of waves which start ventrally and pass over the flanks to the back (Dry, 1926; Butcher, 1934). In our colony of randomly mated albino rats the first wave begins at about 5 weeks of age and is complete 3 weeks later; the second wave starts at 8½–9 weeks of age and is not complete until a further 12–14 weeks have elapsed. In both these waves dorsal hairs are longer than ventral ones, and this appears to be due to a longer growing period rather than to any differences in the rate of growth (Johnson, 1958a). Haddow & Rudall (1945) demonstrated that such waves of growth are accompanied by increased vascularization of the dermis, and suggested that follicles become active as a response to increased vascularity. Durward & Rudall (1949) seem to have modified this view to the extent of suggesting that vascularization cannot cause follicular activity until a required resting stage has been completed.

THE ACTION OF HORMONES ON SPONTANEOUS HAIR GROWTH CYCLES IN THE RAT

1964 ◽  
Vol 29 (2) ◽  
pp. 193-201 ◽  
Author(s):  
F. J. EBLING ◽  
ELIZABETH JOHNSON
Keyword(s):  
Hair Growth ◽  
Hair Follicles ◽  
Female Rats ◽  
Hair Length ◽  
Growth Cycles ◽  
Hormonal Effects

SUMMARY Hypophysectomy of, or administration of thyroxine to, male or female rats advances the activity of hair follicles in the ensuing wave of growth; administration of propylthiouracil retards it. The effects seem to be more marked in the dorsal and head regions than in the flank or belly. Propylthiouracil does not prevent the activation of the follicle induced by plucking of the club hair. It is suggested that the hormonal effects may be produced indirectly through the dermis. Hypophysectomy increased definitive hair length in females but not in males; thyroxine also produced a small increase and propylthiouracil a decrease which proved to be significant in females, but not in males.

DEVELOPMENT OF THE MECHANISMS INVOLVED IN THE FACILITATORY AND INHIBITORY EFFECTS OF OVARIAN STEROIDS ON THE RELEASE OF FOLLICLE-STIMULATING HORMONE IN THE IMMATURE RAT

1973 ◽  
Vol 58 (3) ◽  
pp. 547-554 ◽  
Author(s):  
L. CALIGARIS ◽  
J. J. ASTRADA ◽  
S. TALEISNIK
Keyword(s):  
Follicle Stimulating Hormone ◽  
Significant Rise ◽  
Feedback Effect ◽  
Female Rats ◽  
Male Rats ◽  
Facilitatory Effect ◽  
Inhibitory Effects ◽  
Immature Rat ◽  
The Central Nervous System ◽  
Stimulating Hormone

SUMMARY Serum follicle-stimulating hormone (FSH) concentration was found to be higher in neonatal female rats than in adults. The values increased to a maximum on day 15 and decreased thereafter. Ovariectomy soon after birth or at 5 days of age induced a significant rise in serum FSH concentration 9 days later. Administration of 10 μg oestradiol benzoate (OB) lowered FSH concentration in both intact and spayed animals. Progesterone (1 mg) injected 3 days after priming female rats with a single dose of 10 μg OB induced, on the same day, a significant rise in serum FSH concentration in animals older than 22 days of age. In younger animals progesterone reversed the effect of OB. The facilitatory effect of progesterone occurred when the hormone was given in the afternoon but not when it was given in the morning. Male rats, although showing the negative feedback effect of OB injection, failed to show the positive feedback effect of progesterone. It is concluded that the central nervous system—hypophysial mechanism responsible for FSH secretion is ready to function before puberty. In female rats initiation of puberty probably depends on the activation of that mechanism by appropriate facilitatory ovarian steroid signals.

The Influence of Adrenaline on Gender Difference in Adenosine Diphosphate-Induced Aggregation of Platelets in the Rat

1988 ◽  
Vol 60 (03) ◽  
pp. 481-485 ◽  
Author(s):  
A O Oyekan ◽  
J H Botting
Keyword(s):  
Fibrinolytic Activity ◽  
Adenosine Diphosphate ◽  
Female Rats ◽  
Male Rats ◽  
Rate Measurement ◽  
Inhibitory Effects ◽  
Adrenaline Infusion ◽  
Induced Aggregation ◽  
Aggregation Of Platelets

SummaryThe role of adrenaline on the inhibitory effects of physiological levels of oestradiol on ADP-induced intravascular aggregation has been studied. Platelets from pro-oestrous female rats aggregated less than those from dioestrous and male rats. Following adrenalectomy, there was no longer any difference(s) in the aggregability of the platelets to ADP in any of the rats. Adrenaline infusion (20 mg kg−1 hr−1) restored platelet aggregation to preadrenalectomy levels in pro-oestrous rate. Measurement of spontaneous fibrinolytic activity of the plasma showed highest value in pro-oestrous rats. Adrenalectomy reduced, while adrenaline infusion increased the fibrinolytic activity. The results suggest that the inhibitory effects of oestradiol on intravascular aggregation are dependent on endogenous adrenaline possibly working through the fibrinolytic pathway.

THE INFLUENCE OF SEX ON THE MATURATION OF THE CENTRAL NERVOUS SYSTEM IN THE ALBINO RAT

1951 ◽  
Vol 7 (3) ◽  
pp. 271-279 ◽  
Author(s):  
J. T. EAYRS
Keyword(s):  
Spinal Cord ◽  
Central Nervous System ◽  
Nervous System ◽  
The Body ◽  
Female Rats ◽  
Male Rats ◽  
Albino Rat ◽  
Litter Mate ◽  
Male And Female Rats ◽  
The Central Nervous System

The growth of the body and central nervous system and the emergence of stereotyped behaviour have been studied in male and female rats during the first 24 days of life. The effects of daily injections of equine gonadotrophin on these measures have also been investigated. The weight of the body and of the central nervous system was significantly less in the female than in the male. The daily administration of 10 i.u. of equine gonadotrophin was without effect on either. The movements of the trunk and limbs concerned in the body-righting reflex became coordinated more slowly in the gonadotrophin-injected animals than in their litter-mate controls. At 15 days old, male rats were able to right in mid-air more successfully than litter-mate females. The placing reflex appeared earlier in the male than in the female. Its appearance was accelerated in the females given gonadotrophin, but not in the males. In the ventral funiculus of the spinal cord of 24-day-old experimental animals, the axis cylinders occupied more space relative to that occupied by myelin than did those of the controls. The total amount of myelin present was unchanged. There was no sex difference in the progress of myelination in the spinal cord. The significance of these findings in relation to the secretion of sex hormones is discussed. It is suggested that the secretion of androgen may be responsible for an acceleration of nervous maturation.

5-HT1B receptor agonist attenuates cocaine self-administration after protracted abstinence and relapse in rats

2021 ◽  
pp. 026988112110192
Author(s):  
Samantha N Scott ◽  
Raul Garcia ◽  
Gregory L Powell ◽  
Sophia M Doyle ◽  
Brielle Ruscitti ◽  
...  
Keyword(s):  
Cue Reactivity ◽  
Fixed Ratio ◽  
Test Session ◽  
Female Rats ◽  
Male Rats ◽  
Inhibitory Effects ◽  
Self Administration ◽  
Training Dose ◽  
Male And Female Rats ◽  
Cocaine Seeking

Background: The 5-HT1B receptor (5-HT1BR) agonist, CP94253, enhances cocaine intake during maintenance of self-administration (SA) but attenuates intake after 21 days of forced abstinence in male rats. Aims: We examined whether CP94253 attenuates cocaine intake in female rats after a period of abstinence, and if these attenuating effects persist or revert to enhancing cocaine intake during resumption (i.e. relapse) of daily cocaine SA. Methods: Male and female rats trained to lever press on a fixed ratio 5 schedule of cocaine reinforcement underwent ⩾21 days of forced abstinence. They were then tested for the effects of CP94253 (5.6 mg/kg, SC) or vehicle on cocaine SA. During the test session, rats had 1-h access to the training dose of cocaine (0.75 mg/kg, IV) followed by 1-h access to a lower cocaine dose (0.075 mg/kg, IV). Rats then resumed cocaine SA for 15 days to mimic relapse and were retested as done previously. Subsequently, rats underwent abstinence again (21–60 days) and were tested for CP94253 effects on locomotion and cue reactivity (i.e. responding for light/tone cues previously paired with cocaine infusions). Results: Regardless of sex, CP94253 decreased cocaine intake after abstinence and during resumption of SA and decreased cue reactivity while having no effect on locomotion. Conclusions: CP94253 decreases cocaine intake and cocaine seeking in both males and females even after resumption of cocaine SA. These findings suggest that the inhibitory effects of CP94253 observed after abstinence are long-lasting, and therefore, 5-HT1BR agonists may have clinical efficacy as anti-relapse medications for cocaine use disorders.

scholarly journals ENLARGEMENT OF THE ADRENAL CORTEX IN EXPERIMENTAL UREMIA

1927 ◽  
Vol 46 (3) ◽  
pp. 429-442 ◽  
Author(s):  
Eaton M. MacKay ◽  
Lois Lockard MacKay
Keyword(s):  
Adrenal Cortex ◽  
Adrenal Glands ◽  
Female Rats ◽  
Male Rats ◽  
Cortical Tissue ◽  
Albino Rat ◽  
Irregular Distribution ◽  
Storage Materials ◽  
Adrenal Enlargement ◽  
Medullary Cells

The production of an experimental uremia in the albino rat by removal of both kidneys is followed by hypertrophy of the adrenal glands. In the case of male rats 90 days of age this adrenal enlargement amounted to 65 per cent and in the case of female rats 180 days of age 47 per cent. The increase in the size of the whole gland is due entirely to hypertrophy of the cortex. This increase in the volume of cortical tissue amounted to approximately 40 per cent for males and 61 per cent for females and was due in large part to an increase in the size of the cells. The content of water and material soluble in fat solvents was higher in the uremic than the control glands. However after subtraction of such storage materials a true hypertrophy of the cortex still remained. It amounted to 21 per cent. Histologically the stainable fat had a more irregular distribution and was present in lesser amount in the adrenals from the uremic animals. The capillaries of the medulla and reticular cortex were distended. The nuclei of both the cortical and medullary cells were swollen and stained faintly.

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