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Niels Einer-Jensen

Publications and source records attributed to Niels Einer-Jensen.

8 recordsLinked to original sources
PubMed2006

Presence and significance of temperature gradients among different ovarian tissues.

After recalling male gonadal physiology in respect of tissue temperatures within the scrotal sac, and raising questions concerning abdominal testes, attention turned to mature Graafian follicles and ovarian stroma. Temperature gradients between such tissues were summarized for human, rabbit, pig, and cow, and generally fell in the range of 1.3-1.7 degrees C: follicles were always cooler than stroma. Measurements were made principally by means of a thermo-sensing camera at midventral laparotomy, but also using microelectrodes or thermistor probes sited in the follicular antrum of rabbits and pigs, respectively. When thermo-imaged under the fimbriated extremity of the Fallopian tube, mature pig follicles and stroma could still be distinguished. Such follicles cooled slightly more rapidly during the first 10 s of a 60-s recording interval, after which curves for the two tissues remained parallel. Arresting ovarian blood supply for 5 min had a negligible influence on the temperature differentials. Endoscopy in three models recorded mean differentials of 0.6 +/- 0.1 degrees C - 1.1 +/- 0.1 degrees C between follicles and stroma, but such follicles had not attained mature diameter. Temperature gradients were thought to be generated at least in part by endothermic reactions within mature follicles, reflecting hydration of large extracellular matrix molecules such as proteoglycans. A contribution to the cooling process from the products of leukocyte activity in the follicle wall and antrum could also be involved. Temperature gradients would be maintained locally by counter-current heat exchange mechanisms and, in this context, the microvasculature and lymphatic flow of individual follicles were found to be appropriate. Observations on the temperature of preovulatory follicles appear relevant to procedures of in vitro maturation and in vitro fertilization.

Animals↗
PubMed2004

Preferential transfer of endogenous ovarian steroid hormones to the uterus during both the follicular and luteal phases.

BACKGROUND: Ovarian steroids are thought to be released into the systemic circulation and reach the uterus via the uterine arteries. However, results of experimental and clinical studies suggest the existence of local transfer of steroids from the ovary to the uterus. This study aimed to verify the existence of preferential distribution of ovarian steroids to the uterus in the two phases of the menstrual cycle. METHODS: We performed parallel measurements of serum levels of estradiol and progesterone in the systemic circulation (arterial and venous) and in the uterine vessels in two groups of cycling women; one group were in the follicular phase (six women) and the other group were in the luteal phase (10 women) of the menstrual cycle. RESULTS: Both in the follicular phase and in the luteal phase groups, mean estradiol levels in the uterine blood were significantly higher than in both sides of the systemic circulation (F = 7.30, df = 15, P < 0.006; and F = 4.70, df = 27, P < 0.02). Similar results were obtained in the luteal phase group for progesterone (F = 9.38, df = 27, P < 0.0001). Both estradiol and progesterone levels in arterial and venous systemic blood were similar. CONCLUSIONS: The results of this study demonstrate that ovarian steroid levels are significantly higher in the uterine vessels than in both sides of the systemic blood circulation, and strongly suggest the existence in the female pelvis of mechanisms of local distribution of ovarian hormones.

Adult↗
PubMed2004

Blood to the cornual area of the uterus is mainly supplied from the ovarian artery in the follicular phase and from the uterine artery in the luteal phase.

BACKGROUND: The blood supply to the uterus is provided by the uterine and ovarian arteries, which form anastomoses. Yet the flow direction through this anastomoses and the primary source of blood supply to the tubes and uterine cornua remains unknown. To clarify this issue, we studied the spatial propagation of temperature changes following cooling of the upper vaginal area. METHODS: A thermocatheter with eight measurement points at 5-mm intervals was inserted into the uterus of nine women in the follicular phase and 11 in the luteal phase. The distal tip was positioned in the cornual area and temperatures were registered every 2 s. The vagina was then cooled for 7 min with 25 degrees C saline. RESULTS: The pattern of uterine cooling based on local counter-current transfer differed between the follicular and luteal phase. Cooling of the cornual area was significantly lower in the luteal phase compared with the follicular phase, indicating a shift in the prevailing source of arterial supply in that area following ovulation. CONCLUSIONS: The divide between the territories irrigated by the uterine and ovarian arteries moves between the follicular and luteal phase. This constitutes the first description of a functionally determined shift in the territorial divide of two vascular systems, and has numerous practical implications.

Adult↗
PubMed2004

The vascular cast of the human uterus: from anatomy to physiology.

The blood supply to the uterus originates mainly from the uterine artery. However, the uterine and ovarian arteries form anastomoses bilaterally. Controversy exists about the direction of the flow in the anastomoses and thus the origin of the arterial supply to the tube and tubal part of the uterus. A similar arcade is formed by the vaginal and uterine arteries. We have investigated the vascular border of supply between the uterine and ovarian arteries in postmenopausal women, which was positioned in the uterus 1-2 cm from the tube. A similar result was found in younger, ovulating women. However, the border between the territories irrigated by the uterine and ovarian arteries differs between the follicular and luteal phase; more uterine tissue is perfused from the ovarian artery when a large follicle is present. This constitutes the first description of a functionally determined shift in the territorial divide of two vascular systems and has numerous practical implications. The venous system copies the arterial one with one major exception: some of the uterine veins join the ovarian outlet. The close contact between veins and arteries facilitates transfer of substances, thus forming semilocal systems of regulation; for example, the ovary locally influences the function of the ipsilateral tube and part of the uterus. From a therapeutic point of view, it has been documented that application of progesterone to the vagina creates high uterine concentrations due to local vascular transfer.

Arteries↗
PubMed2003

Local vascular pathway for progesterone transfer to the brain after nasal administration in gilts.

In the present study we examined whether local transfer of intranasally administrated tritiated progesterone (3H-P4) would increase its concentration in blood supplying the brain and hypophysis in comparison with other organs. Additionally, the effect of estrous cycle on the P4 transfer was evaluated on isolated gilts' heads. In the first experiment 3H-P4 was instilled into the nasal cavities of anaesthetized, immature pigs (n=10). Simultaneous blood samples were collected for radioactivity measurement every minute from the same occluded carotid artery through two catheters; one catheter was pointed towards the head, the other one towards the heart. In eight animals the ratio calculated between the 'head' and 'heart' samples was significantly (p<0.05) higher than 1 and reached a mean (+/- SEM) level of 3.23 +/- 0.81. In two animals a much higher ratio was observed. A head/heart ratio>1 indicates an existence of local transfer of 3H-P4 from venous blood to the carotid blood. In the second experiment, heads of 26 mature, cycling gilts were perfused through the right carotid artery with autologous blood. The outflow from the left carotid artery was collected as 1 min samples. 3H-P4 was infused into the angularis oculi veins. Transfer of 3H-P4 from the venous blood into the arterial blood reached the mean (+/- SEM) level of 4.11 +/- 1.08 pg/ml on days 2-4, 3.2 +/- 0.70 on days 17-21 and 0.94 +/- 0.22 pg/ml on days 15-16 of the estrous cycle. No 3H-P4 transfer was observed on days 9-11. These findings demonstrate that nasally administered progesterone can reach the brain in locally higher concentration through the vascular pathway. Moreover, the between-vessel transfer of P4 is significantly affected by the stage of the estrous cycle.

Administration, Intranasal↗
PubMed2002

Can intubation harm the brain in critical care situations? A new simple technique may provide a method for controlling brain temperature.

Many animal species are able to keep the brain temperature some degrees centigrade lower than the deep body temperature when exposed to environmental heat stress. The lower temperature is based on cooling of the nasal venous blood through the respiratory airflow and local counter-current transfer of heat between venous and arterial blood in the cavernous sinus-carotid artery complex. Anaesthetized, intubated animals do not have any air flow through the nasal cavities. However, when the nasal cavities were flushed with oxygen, the deep brain temperature dropped within minutes and returned to previous values when the oxygen flushing was stopped. Cooling was found in animals with a rete mirabile (pigs), and in animals without a rete (rats). If a similar cooling mechanism is present in man (no rete) under intensive care, a simple flushing of the nasal cavities with gas will protect the brain against hyperthermal damage.

Animals↗
PubMedDate not supplied

Nasal administration.

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Administration, Intranasal↗