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Medical Sciences	50%

Selected Abstracts

Adaptations of amphibious fish for surviving life out of water

FISH AND FISHERIES, Issue 3 2005
Martin D J Sayer
Abstract There are a small number of fish species, both marine and freshwater, that exhibit a truly amphibious habit that includes periods of aerial exposure. The duration of emersion is reflected in the level of physical and physiological adaptation to an amphibious lifestyle. Fish that are only briefly out of water retain predominantly aquatic attributes whereas there are semi-terrestrial species that are highly adapted to prolonged periods in the aerial habitat. Desiccation is the main stressor for amphibious fish and it cannot be prevented by physiological means. Instead, amphibious fish resist excessive water loss by means of cutaneous modification and behavioural response. The more terrestrially adapted fish species can tolerate considerable water loss and may employ evaporation to aid thermoregulation. The amphibious habit is limited to fish species that can respire aerially. Aerial respiration is usually achieved through modification to existing aquatic pathways. Freshwater air-breathers may respire via the skin or gills but some also have specialized branchial diverticula. Marine species utilize a range of adaptations that may include modified gills, specialized buccopharyngeal epithelia, the intestine and the skin. Areas of enhanced respiratory activity are typified by increased vascularization that permits enhanced perfusion during aerial exposure. As with other adaptations the mode of nitrogenous elimination is related to the typical durations of emersion experienced by the fish. Intertidal species exposed on a regular cycle, and which may retain some contact with water, tend to remain ammoniotelic while reducing excretion rates in order to prevent excessive water loss. Amphibious fish that inhabit environments where emersion is less predictable than the intertidal, can store nitrogen during the state of emersion with some conversion to ureotelism or have been shown to tolerate high ammonia levels in the blood. Finally, the more amphibious fish are more adapted to moving on land and seeing in air. Structural modifications to the pectoral, pelvic, dorsal and anal fins, combined with a well-developed musculature permit effective support and movement on land. For vision in air, there is a general trend for fish to possess close-set, moveable, protruberant eyes set high on the head with various physical adaptations to the structure of the eye to allow for accurate vision in both air and water. [source]

Night-time science with large solar telescopes: The magnetic Sun through time

ASTRONOMISCHE NACHRICHTEN, Issue 6 2010
2Article first published online: 18 JUN 2010, S.C. Marsden
Abstract Today the Sun has a regular magnetic cycle driven by a dynamo action. But how did this regular cycle develop? How do basic parameters such as rotation rate, age, and differential rotation affect the generation of magnetic fields? Zeeman Doppler imaging (ZDI) is a technique that uses high-resolution observations in circularly polarised light to map the surface magnetic topology on stars. Utilising the spectropolarimetric capabilities of future large solar telescopes it will be possible to study the evolution and morphology of the magnetic fields on a range of Sun-like stars from solar twins through to rapidly-rotating active young Suns and thus study the solar magnetic dynamo through time. In this article I discuss recent results from ZDI of Sun-like stars and how we can use night-time observations from future solar telescopes to solve unanswered questions about the origin and evolution of the Sun's magnetic dynamo (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Reproductive hormonal changes and catamenial pattern in adolescent females with epilepsy

EPILEPSIA, Issue 9 2008
Hamed A. El-Khayat
Summary Purpose: We aimed to evaluate the effect of epilepsy on the reproductive hormones levels among female patients, and to investigate the frequency of catamenial pattern of seizures. Methods: A total of 42 female patients with epilepsy and 21 healthy females (control group) were included. Subjects were at least 2 years postmenarche with regular cycles. Symptoms of premenstrual syndrome (PMS) were assessed using calendar of premenstrual experience scoring. Patients were evaluated for catamenial pattern of seizures. Levels of FSH, LH, estradiol (E), and progesterone (P) were assessed for all subjects in the three phases of the cycles. Pelvi-abdominal ultrasound was performed near time of ovulation, to follow up size of mature follicle. Results: Symptoms of PMS were not different in patients and controls, or in patients with and those without catamenial tendency. In both perimenstrual (M) and midluteal phases, FSH and P levels were lower and E/P ratio higher in patients group. There was a catamenial pattern of seizures in 31% of patients (53.8% M C1; 46.15% inadequate luteal phase C3pattern). Patients with C3pattern showed lower P levels in the midluteal phase compared to patients with noncatamenial pattern, to those with C1pattern or to controls. Patients with C1pattern had lower P levels than controls in the M phase. Conclusion: There was evident disruption in the reproductive hormones in female patients with epilepsy with lower FSH and P levels and higher E/P ratio. A total of 31% of patients showed catamenial pattern of seizures (C1and C3patterns) that was significantly related to P withdrawal. [source]

Ethnicity and fetal growth in Fiji

AUSTRALIAN AND NEW ZEALAND JOURNAL OF OBSTETRICS AND GYNAECOLOGY, Issue 4 2004
Matthews MATHAI
Abstract Background:, Indigenous Fijians and the descendants of Asian Indians constitute the two major ethnic groups in Fiji. There are differences between the two groups in perinatal outcomes. Aims:, To study fetal growth patterns in the two ethnic groups and to ascertain the influence, if any, of ethnicity on fetal growth. Methods:, A longitudinal study was carried out on women with sure dates, regular cycles, no known risk factor complicating pregnancy and having their first antenatal examination before 20 weeks. Symphysis-fundal height, biparietal diameter, abdominal circumference and femur length were measured by the same observer at recruitment and at follow-up visits until delivery. Infant measurements were recorded soon after birth. Results:, Indian babies were on average 795 g lighter, had 5.5 days shorter mean length of gestation and slower growth of biparietal diameter and abdominal circumference when compared to Fijian babies. Ethnicity of the mother was significantly associated with the difference in growth even after adjusting for other factors known to influence fetal growth. Conclusion:, Given the ethnic differences in fetal growth and maturation, it would be appropriate to use ethnicity-specific standards for perinatal care in Fiji. [source]