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PubMed2006

Magnetic resonance imaging and the detection of fetal brain anomalies, injury, and physiologic adaptations.

PURPOSE OF REVIEW: Magnetic resonance imaging is playing an increasingly prominent role in depicting brain maturation, especially gyral formation that follows a temporospatial pattern, and in detecting developmental abnormalities of the cortex and other brain sectors. Knowledge of the technical advantages and limitations of in-utero magnetic resonance imaging techniques, relative to those of the postnatal period, is essential to optimize magnetic resonance sequences for early diagnosis. This includes an understanding of the changes in both brain anatomy and magnetic resonance signals that occur with an increase in gestational age. RECENT FINDINGS: Magnetic resonance imaging has evolved has an important adjunct in the diagnosis of brain malformations, particularly in the late-second or third trimester. Noxious conditions elicit more of a chronic rather than acute response in the fetal brain, which differs from that observed postnatally. Clinical applications of proton magnetic resonance spectroscopy may help elucidate fetal brain maturation and its abnormalities from a metabolic point of view. SUMMARY: Indications for fetal brain magnetic resonance imaging have increased because of improvements in magnetic resonance techniques and the ability to detect subtle changes within the cerebral parenchyma, especially in fetuses at increased risk of brain damage.

Brain↗
PubMed2000

Physiological adaptation to low temperatures of strains of Rhizobium leguminosarum bv. viciae associated with Lathyrus spp.(1).

Strains of Rhizobium leguminosarum bv. viciae, isolated from the legume species Lathyrus japonicus and Lathyrus pratensis in northern Quebec (Canada), showed different capacities for growing at low temperature. In the present study, we investigated some mechanisms related to cold adaptation. Two cold-adapted strains (psychrotrophs) were compared to a poorly adapted strain and to a cold-sensitive strain (reference strain) for freezing survival, protein induction and fatty acid composition under low temperature. Following cold shocks (25 degrees C to 10, 5 and 0 degrees C), a common 6.1-kDa CSP (cold shock protein) was induced in all strains, but the total number of CSPs synthesized at 0 degrees C was higher in cold-adapted strains than in the cold-sensitive strain. The synthesis of CAPs (cold acclimation proteins) was observed under continuous growth at 5 degrees C in all three strains capable of growth at this temperature. Levels of survival after 24 h at -80 degrees C where higher in cold- (79%) and poorly adapted (64%) strains than in the cold-sensitive strain (33%), but a 2-h acclimation period at 5 degrees C before freezing doubled the survival of the cold-sensitive strain. Low temperature conditions affected similarly the fatty acid composition of all strains, regardless of their cold adaptation level. The proportion of unsaturated fatty acids increased significantly with the lowering of growth temperature from 25 to 5 degrees C, but showed a tendency to decrease after a cold shock from 25 to 5 degrees C. A specific unsaturated fatty acid, cis-12 octadecanoic acid, was produced during growth at 5 degrees C. The unsaturated cis-vaccenic acid was the principal component under all conditions. The cold adaptation trait was weakly reflected in symbiosis with the agronomic legume, Lathyrus sativus, with which one cold-adapted strain showed a slightly higher nitrogenase activity and shoot dry matter yield than a commercial strain under a sub-optimal temperature regime.

Journal Article↗
PubMed1982

Physiological adaptation to the loss of amino acid transport ability.

A strain of Neurospora crassa devoid of constitutive amino acid transport ability can utilize arginine as the sole nitrogen source. Nitrogen starvation, presence of arginine, and mutational inactivation of the general permease are key factors in signaling production of an extracellular enzyme which removes the alpha-amino group from the amino acid.

Amino Acids↗
PubMed2006

Experimental ischemic cardiomyopathy: insights into remodeling, physiological adaptation, and humoral response.

Ligation of the left anterior descending coronary artery (LAD) is used to induce experimental myocardial infarction (MI). Most previous studies have focused on the early postoperative period, while data on mid-term follow-up are scanty. This study examined the mid-term effects of LAD ligation in 95 MI rats and 28 controls. The following parameters were evaluated: systemic blood pressure (SBP), heart rate (HR), and plasma brain natriuretic peptide (BNP) level. In addition, M-mode and B-mode echocardiography, histologic examinations, and cardiac hydroxyproline assays were performed. Forty-seven perioperative and 5 late deaths were recorded. Left ventricular dilation, observed 1 mo after MI, did not progress with time. Septal thickening was similar in the 2 groups, while wall thickening was lower in the MI rats at 1 mo only. Stroke volume was diminished in MI rats, while cardiac output was depressed only at 1 and 2 mo, due to increased heart rate. SBP was unchanged and plasma BNP level was similar in the 2 groups. The infarcted area (mean +/- SD) was 35 +/- 10%. The ventricles in MI rats were heavier and had increased hydroxyproline content. In conclusion, these data show that LAD ligation is not only a model of acute MI, but at mid-term it provides a model of chronic ischemic dilated cardiomyopathy.

Animals↗
PubMed1989

[Physiologic adaptation of the thermal manikin].

At present time thermal manikins (TM) are used as standard method to determine the thermal quality of clothing. Besides, in the last time TM's apply to estimate indoor climate. Now used types of TM enable quantitative assertions on human convective and conductive heat exchange, as for the whole body as for different parts. The limited factor for this heat flow is the topical value of TM's skin temperature which is regulated by software. As a rule, this temperature is the same like human's skin temperature at thermal comfort conditions. Distal change of skin temperature takes a leading part to determine thermal conditions which are still tolerable regarding human thermoregulation. The influence of this kind of thermal regulation on topical convection and conductive heat exchange was examined by variation of TM's skin temperature on a concrete indoor situation and defined clothing and metabolic conditions.

Body Temperature Regulation↗
PubMed1989

[A heart rate adaptable "physiologic" pacemaker. Is the effort worthwhile?].

The dual-chamber pacemaker provides an approximately physiologic cardiac action in patient with 3rd degree AV-block and preserved sinoatrial function. Newly developed so-called rate-responsive systems are now available. Initial clinical experience has been reported with pacemakers controlled via respiration rate, activity, central venous blood temperature, or intracardially measured QT-interval. The sensitivity and specificity of rate regulation like the effort of implantation and setting is not completely satisfactory and adequate until now. At the present time, such systems are being implanted mainly according to individual indications. Before a general use can be recommended, several problems still remain to be solved, in particular the question as to what therapeutic advantage is to be expected with respect to the underlying disease, arrhythmia and patient group.

Bradycardia↗
PubMed1986

Physiological adaptation of the heart to pathological overloading.

Chronic overloading of the rat heart induces a cascade of adaptational events that compensate for the increase in work. At the myocardial level there are two types of adaptational mechanisms: qualitative, represented by the isomyosin changes leading to an improved efficiency; and quantitative, the hypertrophy. We present new approaches exploring possible adaptational changes at other levels within the myocardial cell. Studies of heart overload were performed either in young rats with experimental aortic stenosis or in humans with chronic compensatory hypertrophy. By means of double immunofluorescence labeling of isolated myocytes with anti-V1 and anti-V3 myosin immunoglobulins, we showed that the shift from high- to low-ATPase isomyosins occurs rapidly after aortic stenosis (2-3 days). Cardiac myocytes were shown to be poor in tubulin but a microtubule pattern was clearly visualized by an immunofluorescence approach. Their role in the onset of adaptational processes after aortic stenosis in not yet clear. On the other hand, we showed that in humans, contrary to small rodents, the adaptational process at the isomyosin level is very small or nonexistent.

Animals↗
PubMed1999

Cannibalism facilitates the use of a novel environment in the flour beetle, Tribolium castaneum.

Cannibalism is well known to affect both the population dynamics and the competitive relationships of organisms. Cannibalistic behaviour commonly increases in stressful conditions, such as when density is high or food is scarce, and cannibals often obtain a nutritional benefit. Might cannibalism also increase in a novel environment to which a population is poorly adapted physiologically? Moreover, might cannibalistic behaviour provide enough of a nutritional advantage in a nutritionally stressful environment to rescue individuals from its adverse effects and thus permit colonization and range expansion? Previous work has shown that oat flour is a particularly stressful environment for Tribolium castaneum. In the study reported here, egg cannibalism by two strains of T. castaneum was significantly enhanced in oat flour, and egg eating rescued larvae from the adverse demographic effects of this poor environment. Development time of the cannibals was accelerated almost to the level seen for individuals reared in the nutritionally superior environment (wheat plus brewer's yeast). Their survival and fecundity also increased relative to individuals reared in oat flour without the opportunity to cannibalize. A sib analysis revealed that for larvae reared in the presence of victim eggs, the extent of cannibalism was genetically variable, so that this trait could evolve, given a selective benefit exceeding its cost. These results suggest that colonization of a marginal new environment could be facilitated by enhanced rates of cannibalism. The possible interplay between cannibalism and physiological adaptation to a new environment is discussed.

Adaptation, Physiological↗