Observations on the sex ratio and the position of the lactating mammary gland in the brush-tailed possum, Trichosurus vulpecula (Kerr) (Marsupialia)

1972 ◽  
Vol 20 (2) ◽  
pp. 131 ◽  
Author(s):  
RM Hope
Keyword(s):  
Mammary Gland ◽  
Sex Ratio ◽  
Age Groups ◽  
Differential Mortality ◽  
Sex Ratio At Birth ◽  
Significant Excess ◽  
Lactating Mammary Gland ◽  
Left And Right ◽  
Significant Regression ◽  
The Right

Data on age, sex, and location of the lactating mammary gland in T. vulpecula have been obtained from animals captured in 14 different localities in southern Australia. There is no evidence of differences between localities in the sex ratio of pouch young and the overall totals of 113 males and 94 females do not differ significantly from equality. When these data are combined with data on the sex ratio of T. vulpecula pouch young obtained by other workers, there is a consistent and significant excess of males. On partitioning the data obtained in this study into four age groups of 50 days, the 0 to 50-day group contains a significant excess of males, whereas the older groups show a sex ratio close to 1. Also, there is a significant regression of sex ratio on age, the proportion of males decreasing with increasing age. These observations may be accounted for by proposing that the sex ratio at birth favours an excess of males, and that differential mortality between the sexes occurs during pouch life. A sample of adults and independently living juveniles from Rocky River, Kangaroo I., S.A., contains a highly significant excess of males (202 males, 92 females). In all other population samples the sex ratio is close to 1. In samples from two of the localities, namely Rocky River and Adelaide, there is a significant departure from equality with respect to the number of pouch young suckling from the left and right teat. At Rocky River the right teat appears to be favoured, while in Adelaide the situation is reversed.

Studies on the sex-ratio and related phenomena. (7) The foetal sex-ratio in the pig

1925 ◽  
Vol 15 (3) ◽  
pp. 284-299 ◽  
Author(s):  
A. S. Parkes
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Inverse Correlation ◽  
Differential Mortality ◽  
Average Weight ◽  
Significant Difference ◽  
Approximate Equality ◽  
Left And Right ◽  
Males And Females ◽  
The Right

1. Of 583 pig foetuses of all ages, 331 were found to be males and 252 females, giving a male percentage of 56·8, which is much higher than the approximate equality between the sexes that seems to exist at birth. This result confirms Jewell, who found a male percentage of 55 among 1000 cow foetuses.2. These 583 pig foetuses when classified by weight (0–100 gm., 101–300 gm., 301+gm.) gave the following percentages of males for the respective groups, 59·1, 57·0, 53·2. In other words, the percentage of males decreases as gestation proceeds, a result which can only be brought about by a differential mortality of males and females. It would appear that the percentage at conception must be very near 60 per cent. or 150 males per 100 females.3. The sex-ratios of foetuses from the left and right cornua show no significant difference, 55·0 for the right and 54·7 for the left.4. The males were found to average about 7 per cent. heavier than the females.5. There seems to be an inverse correlation between the number of foetuses in a horn and their average weight. Foetuses from the left cornu have a slightly greater weight than those from the right, and this may be connected with the slightly inferior fertility of this horn.6. The excess of males at conception is discussed in the light of the implications of the chromosome mechanism of sex determination, and reference is made to the greater mortality of the males.

The Breeding Cycle of the Female Humpback Whale, Megaptera nodosa (Bonnaterre)

1958 ◽  
Vol 9 (1) ◽  
pp. 1 ◽  
Author(s):  
RG Chittleborough
Keyword(s):  
Mammary Gland ◽  
Sex Ratio ◽  
Post Partum ◽  
Humpback Whale ◽  
The Other ◽  
Breeding Cycle ◽  
Sex Ratio At Birth ◽  
Modal Length ◽  
The Third ◽  
Normal Period

The gestation period in the humpback whale is of almost 12 months' duration, most conceptions occurring early in August with parturition at the beginning of the following August. The modal length of calves at birth is 14 ft. The sex ratio at birth is 51.4 per cent. males to 48.6 per cent. females. Twin foetuses are occasionally recorded. There is no preference towards either right or left ovary or uterine cornu with regard to ovulation or pregnancy. The breaking of the umbilical cord at birth is described. The histological appearances of the mammary gland during advanced pregnancy and during lactation are described and illustrated. Upon the evidence presented it is concluded that lactation in this species extends over 104 months, suckling generally commencing in mid August and terminating at the end of the following June. The composition of the milk has been determined during various stages of lactation. Oestrous cycles rarely occur during pregnancy, but examples of ovulation following shortly after parturition, while the females are suckling their calves, are cited. It is shown that when the calf is lost at or soon after birth, oestrous cycles usually recommence at once. Where the calf is suckled for the normal period (10½ months) there is no anoestrous period following the end of lactation as oestrous cycles recommence in July, immediately after (occasionally just before) weaning at the end of June. Three types of breeding cycle are shown for the humpback whale. In the most common cycle, absence of the post-partum ovulation, or its occurrence without conception, results in one calf in 2 years. On the other hand, a successful postpartum ovulation results in two calves in 2 years. In the third type of cycle, loss of the first calf at or just after parturition is balanced by a second pregnancy succeeding immediately afterwards. This results in two pregnancies in 2 years with only one calf reared.

scholarly journals A Study to Evaluate and Compare Right and Left Condylar Discrepancy between Centric Relation and Maximum Intercuspation in Three Age Groups

2016 ◽  
Vol 5 (1) ◽  
pp. 984
Author(s):  
Chetan Hegde ◽  
Swapnil Mahade ◽  
Krishna Prasad D.
Keyword(s):  
Age Groups ◽  
Orientation Relation ◽  
Group Iii ◽  
Area Of Interest ◽  
Centric Relation ◽  
Group I ◽  
Left And Right ◽  
The Mean ◽  
Group Ii ◽  
The Right

<strong><em>Background</em>:</strong>Since discrepancy between centric relation and maximum intercuspation has been an area of interest for dental fraternity for decades, the study was conducted to expand the concepts of the same when age is taken into consideration.<p><strong>Objective:</strong> This study was conducted to assess and measure the discrepancy between centric relation (CR) and maximum intercuspation (MI) at right and left condyles in three age groups, compare the discrepancy at right and left condyles between three age groups and right and left side condyles within the same age group.</p><p><strong>Methods:</strong> Sixty healthy subjects were selected and divided into three groups of twenty subjects each. Group I: 18-25 years, Group II: 30-45 years and Group III: more than fifty years. Preliminary impressions were made. Orientation relation was transferred to a semi-adjustable arcon articulator. Subjects were guided into centric relation using Dawson's bimanual manipulation technique and centric interocclusal record was made. The mandibular cast was related to the maxillary cast using centric interocclusal record. The casts were then allowed to fall into maximum intercuspation and the distance that the condylar analogues had moved was measured using Feeler gauge.</p><p><strong><em>Results:</em></strong> The mean CR-MI discrepancy in Group I was 0.417±0.137 mm and 0.364±0.123 mm, Group II was 0.528±0.160 mm and 0.512±0.158 mm and Group III was 0.873±0.228 mm and 0.815±0.172 mm at the right and left condyles respectively.</p><p><strong><em>Conclusion:</em></strong> Within the limitations of the study it was concluded that all the sixty subjects had a CR-MI discrepancy in both left and right condyles. The variation in discrepancy between the three age groups was found to be very highly significant.</p>

scholarly journals Measurement of the Mammary Gland Cistern of Dairy Ewes

2019 ◽  
Vol 67 (4) ◽  
pp. 957-961
Author(s):  
Pavol Makovický ◽  
Melinda Nagy ◽  
Milan Margetín ◽  
Janka Poráčová ◽  
Michal Milerski ◽  
...  
Keyword(s):  
Mammary Gland ◽  
Average Length ◽  
Variance Analysis ◽  
Dairy Ewes ◽  
Stage Of Lactation ◽  
Length Width ◽  
Left And Right ◽  
The Difference ◽  
The Right ◽  
Data Length

At the 3rd and 5th month of lactation, using the ALOKA‑250 ultrasonograph with a 3.5 MHz probe, the udder cistern size of the breed Improved Valachian (IV) and the crossbreed IV x Lacaune (IV x LC) was surveyed. Using the method from side 72 ewes were measured, in which the probe was placed in the inguinal‑abdominal fold. Variance analysis was used to evaluate the obtained data (length, width and udder cistern area), taking into account the effect of the genotype, stage of lactation and lactation order. The average length, width and area of the left udder cistern (LUC) was 80.72 mm; 33.53 mm and 1907 mm2; for the right udder cistern (RUC) 79.44 mm; 33.01 mm and 1851 mm2. The genotype had a statistically significant effect on the LUC as well as the RUC size (P < 0.05 to 0.001). The LUC area of the IV x LC ewes was 32.7% bigger than at IV (2175 mm2 and 1639 mm2, respectively), and the difference of the RUC was up to 51% in favour of the crossbreed (2227 mm2 and 1475 mm2, respectively). This may be due to laterality, the natural asymmetry found in many mammals. The variability in the observed variables of the left and right udder cisterns was greater in crossbreeds than in the purebred IV ewes.

A positive correlation between population size and egg-content in Metastrongylus apri (Gmelin, 1790)

Parasitology ◽  
1971 ◽  
Vol 63 (2) ◽  
pp. 191-194 ◽  
Author(s):  
J. B. Dixon
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Sex Ratios ◽  
Positive Correlation ◽  
Significant Tendency ◽  
Large Numbers ◽  
Left And Right ◽  
The Right ◽  
Two Populations ◽  
Microbiological Research

SUMMARYObservations on the egg-content of 78 counted populations of Metastrongylus apri showed that there was a positive correlation between population size and mean egg-content per female. In bilateral infections within one host, a significant tendency was shown for the larger of the two populations to outstrip the smaller in mean egg-content per female. There was no correlation between sex-ratio and mean egg-content. It is suggested that the effect of the host's defences against individual parasites is mitigated when large numbers of parasites are present.A positive correlation was found between the sex-ratios of populations in left and right lungs, and there was a significant predilection of M. apri for the right lung.I am indebted to Dr S. Peto, Microbiological Research Establishment, Porton, Wilts, for statistical advice, and to T. Wall and Sons Ltd., Atlas Road, London, N.W. 10, for access to abattoir material.

scholarly journals The influence of functional skewness on prognosis of cancer of mammary gland

2002 ◽  
Vol 1 (1) ◽  
pp. 36-40
Author(s):  
L. E. Erendeeva ◽  
M. V. Zavyalova ◽  
E. M. Slonimskaya ◽  
V. M. Perelmuter
Keyword(s):  
Breast Cancer ◽  
Mammary Gland ◽  
Left Breast ◽  
Morphological Features ◽  
Left And Right ◽  
The Right ◽  
Worse Prognosis

In this study the features of developing cancer both in the left and right breast have been compared. We examined 45 parameters which characterize clinical as dell as morphological features of breast cancer. Of all parameters investigated only 5 are more informative ones. They show that breast cancer is developing differently in the right and the left breast. We conclude that localization of cancer in the right breast has a worse prognosis. The results obtained are discussed.

Ontogenetic Trends in Gnostic Hand Function in 3- to 12-Yr.-Old Children

2003 ◽  
Vol 96 (3_suppl) ◽  
pp. 1043-1061 ◽  
Author(s):  
W. van Grunsven ◽  
C. Njiokiktjien ◽  
M. Vranken ◽  
M. Vuylsteke-Wauters
Keyword(s):  
Hand Function ◽  
Age Groups ◽  
Control Analysis ◽  
Correct Reproduction ◽  
Wooden Object ◽  
Intimate Relation ◽  
Left And Right ◽  
The Right ◽  
Right And Left Hands ◽  
Two Age Groups

The intimate relation between the sensory and motor functions of the hands during object manipulation and exploratory touch, the well-known improvement in object handling and constructive performance in ontogenesis and the emergent laterality thereof, assume changes in morphognostic capabilities in children. In this study we tried to corroborate the hypothesis of Mesker that mature and lateralized finger-thumb opposition is preceded by a stage of two-sided manual form agnosia in preschool children, followed by acquisition of morphognosis of the fingers and, finally, the thumbs. This study examined the development of gnostic hand function in 290 children from 3 to 11 years of age who drew the outlines of a meaningless wooden object passively felt with each hand without visual control. Analysis showed a clear ontogenetic change across the two age groups of increasing morphognostic function: 48% of the 6-yr.-olds drew correctly what the fingers of both left and right hands had perceived (thumbs, 14%). Of the 11-yr.-olds 91% and 61% performed perfectly with the right and left hands, respectively. The fingers preceded the thumbs in reproduction by most children, and the correct reproduction by the left thumb precedes that of the right thumb. The ontogenesis of bimanual sensorimotor functioning is discussed in the light of cortical and callosal development.

scholarly journals Greater loss of female embryos during human pregnancy: A novel mechanism

2018 ◽  
Author(s):  
John F Mulley
Keyword(s):  
Sex Ratio ◽  
Human Development ◽  
Follicular Fluid ◽  
Sex Ratio At Birth ◽  
Maternal Condition ◽  
Acceptance Threshold ◽  
Human Pregnancy ◽  
The Right

SummaryGiven an equal sex ratio at conception, we can only explain the excess of human males at birth by greater loss of females during pregnancy. I propose that the bias against females during human development is the result of a greater degree of genetic and metabolic “differentness” between female embryos and maternal tissues than for similarly aged males, and that successful implantation and placentation represents a threshold dichotomy, where the acceptance threshold shifts depending on maternal condition, especially stress. Right and left ovaries are not equal, and neither are the eggs and follicular fluid that they produce, and I further hypothesise that during times of stress, the implantation threshold is shifted sufficiently to favour survival of females, most likely those originating from the right ovary, and that this, rather than simply a greater loss of males, explains at least some of the variability in the human sex ratio at birth.

EFFECT OF LOCALLY IMPLANTED OESTROGEN ON THE RESPONSE OF THE RAT'S LACTATING MAMMARY GLAND TO OXYTOCIN

1973 ◽  
Vol 73 (4) ◽  
pp. 700-712 ◽  
Author(s):  
J. D. Bruce ◽  
X. Cofre ◽  
V. D. Ramirez
Keyword(s):  
Mammary Gland ◽  
Mammary Glands ◽  
Myoepithelial Cells ◽  
Recording System ◽  
Saline Infusion ◽  
High Dose ◽  
Low Doses ◽  
Milk Ejection ◽  
Lactating Mammary Gland ◽  
Small Rise

ABSTRACT On the day following delivery (day 1 of lactation) one abdominal mammary gland was implanted with oestrogen and the contralateral gland received an empty needle. At 2, 5 or 10 days of lactation the rats were anaesthetized with pentobarbital and the nipples of both abdominal glands were cannulated and their pressures recorded by means of transducers coupled to an amplifier and recording system. The normal mammary glands of 5-day lactating rats responded to very low doses of oxytocin (Syntocinon®, Sandoz) (5× 10−8 mU) with a rhythmic elevation in pressure. However, saline infusion also evoked a small rise in intra-mammary pressure. Earlier (2 days) and later (10 days) in lactation the responses were smaller. Oestrogen decreases significantly the milk ejection response to oxytocin, and the effect was maximal at day 10 of lactation. Histological observations confirmed the diminished reaction of the gland to oxytocin, since the milk was retained in the alveoli of rats bearing a mammary-oestrogen implant. A paradoxical rise in pressure was detected in normal as well as in oestrogen-implanted glands when the lowest dose of oxytocin was injected in lactating rats which had previously received a high dose of oxytocin (50 mU or 500 mU). These results reinforce the hypothesis that oestrogen alters the milk ejection response to oxytocin and that the mechanism is probably related to changes in the contractility of the myoepithelial cells.

ÜBER DIE WIRKUNG PHARMAKOLOGISCHER OXYTOCINDOSEN AUF DIE MILCHDRÜSE

1960 ◽  
Vol XXXIV (IV) ◽  
pp. 543-557 ◽  
Author(s):  
B. Berde ◽  
A. Cerletti
Keyword(s):  
Mammary Gland ◽  
Intravenous Administration ◽  
Intravenous Infusion ◽  
Intranasal Administration ◽  
Intramuscular Injection ◽  
Different Types ◽  
Lactating Mammary Gland ◽  
Synthetic Oxytocin

ABSTRACT A study was made of the influence of pharmacological amounts of synthetic oxytocin (»Syntocinon«) on the lactating mammary gland of the rabbit. The drug was given by intravenous infusion, by intramuscular injection and by intranasal administration. Two different types of reaction were noted: a tonic reaction, i. e. a lasting increase in pressure in the mammary gland without significant fluctuations, or a rhythmic reaction, i. e. a series of increases in pressure at more or less regular intervals. In order to elicit reactions approximately identical in intensity and character with those produced by intravenous infusion, it was necessary to give approximately 1.5 to 8.0 times as much by intramuscular injection and approximately 10 to 100 times as much by intranasal administration. Intravenous administration of adrenaline transiently suppressed a long-lasting reaction to oxytocin.

Sign in / Sign up

Export Citation Format

Share Document