Blubber and flipper heat transfer in harp seals

The trunk of marine mammals is encased in a blubber layer which provides thermal insulation that can be changed by circulatory adjustments. The extremities, on the other hand, are poorly insulated but have vascular arrangements constructed for prevention or promotion of heat loss, depending on the thermal state of the animal. We have studied the importance of different body parts as sites for heat dissipation and also assessed the effect of circulatory adjustments on heat transfer through blubber, by combining direct measurements of heat flux from the flippers and trunk with simultaneous recordings of temperature gradients through the blubber and metabolic rates of harp seals (Phoca groenlandica) subjected to water temperatures between 1 and 24 °C. We also determined the thermal conductivity of blubber samples from the same animals after death, and compared this with the insulative properties of live blubber. At the lowest water temperatures, the insulative properties of live blubber were similar to those of dead blubber, and heat loss from the flippers only accounted for 2–6% of the metabolic heat production. As heat load increased with increasing water temperatures, the fraction of heat lost from the flippers increased, to 19–48% at 24 °C, while the fraction lost from the trunk decreased, despite an increase in the convective (circulatory) heat transfer through the blubber layer.     

Sleep in the harp seal (Pagophilus groenlandica). Comparison of sleep on land and in water

Four young harp seals (aged three to five months) were implanted with electrodes for recording electrocorticograms (ECoG) of the two hemispheres, and electrocardiogram, electroculogram, and electromyogram of the neck muscles. In all the seals ECoG slow waves developed simultaneously in both hemispheres, irrespective of whether they slept on land, on the water surface or submerged. Slow-wave sleep (SWS) was present in animals on the water surface and submerged, while paradoxical sleep (PS) occurred only when the animals were submerged. Breathing in SWS could be both regular (pauses less than twenty seconds) and intermittent (pauses lasting up to three minutes alternating with hyperventilation periods). All the PS episodes occurred during single respiratory pauses and ended by waking while the seal ascended to the water surface to breathe. Flipper movements were sometimes observed in SWS, but never in PS. The ability of harp seals to cease respiration during sleep and to sleep under water could be an adaptation to living conditons in the freezing seas.     

Preoptic hypernatremic syndrome and the regulation of water balance in the rat

Lesions of the medial preoptic area in rats cause a transient adipsia and aphagia, with a weight loss of 15–20%. Feeding and drinking behaviours return, with water intakes similar to sham-operated rats. However, the rats remain chronically hypernatremic for a period of at least 2 months. The hypernatremia persists during food deprivation and during stimulation of drinking by extracellular dehydration. No deficiency is evident in urinary concentrating ability or in ability to excrete sodium ions; extrarenal water loss is similar to that of sham-operated rats. The rats do not drink in response to hypertonic saline injection, and they do not retain an imposed water load. A comparison with rats with diabetes insipidus, which avoid hypernatremia by sharply increasing their water intakes, demonstrates that the hypernatremia is related to a dysfunction of intake as well as output. The findings suggest that medial preoptic lesions may reset the set-point for regulation of plasma sodium concentration; they also suggest that the lesions may cause reduced sensitivity to an increase in plasma sodium concentration.     

OX52 is the rat homologue of CD6: evidence for an effector function in the regulation of CD5 phosphorylation

The MRC OX52 monoclonal antibody is a marker of rat T lymphocytes. We have cloned by polymerase chain reaction the rat homologue of CD6, and fluorescein-activated cell sorter analysis and immunoprecipitations using OX52 in COS7 cells transfected with rat CD6 cDNA showed that CD6 is the cell-surface molecule recognized by OX52. Immunoprecipitation analysis showed that CD6 coprecipitated with CD5, which in turn, was coprecipitated equivalently with CD2, CD6, and the T cell receptor (TCR), but the fraction of CD5 associated with CD6 was highly phosphorylated in kinase assays, in marked contrast with the low level of phosphorylation of CD5 associated with TCR or CD2. Examination of protein kinases associating with these antigens showed that paradoxically, CD2 coprecipitated the highest amount of Lck and Fyn. CD6 also associated with Lck, Fyn, and ZAP-70, although at lower levels but additionally coprecipitated the Tec family kinase Itk, which is absent from CD2, CD5, and TCR complexes. Lck together with Itk was the best combination of kinases, effectively phosphorylating synthetic peptides corresponding to a cytoplasmic sequence of CD5. Overall, our results suggest that CD6 has an important role in the regulation of CD5 tyrosine phosphorylation, probably as a result of its unique feature of associating with kinases of different families.     

Dynamics of heat,water, and soluble gas exchange in the human airways: 1. A model study

In order to provide a means for analysis of heat, water, and soluble gas exchange with the airways during tidal ventilation, a one dimensional theoretical model describing heat and water exchange in the respiratory airways has been extended to include soluble gas exchange with the airway mucosa and water exchange with the mucous layer lining the airways. Not only do heat, water, and gas exchange occur simultaneously, but they also interact. Heating and cooling of the airway surface and mucous lining affects both evaporative water and soluble gas exchange. Water evaporation provides a major source of heat exchange. The model-predicted mean airway temperature profiles agree well with literature data for both oral and nasal breathing validating that part of the model. With model parameters giving the best fit to experimental data, the model shows: (a) substantial heat recovery in the upper airways, (b) minimal respiratory heat and water loss, and (c) low average mucous temperatures and maximal increases in mucous thickness. For resting breathing of room air, heat and water conservation appear to be more important than conditioning efficiency. End-tidal expired partial pressures of very soluble gases eliminated by the lungs are predicted to be lower than the alveolar partial pressures due to the absorption of the expired gases by the airway mucosa. The model may be usable for design of experiments to examine mechanisms associated with the local hydration and dehydration dynamics of the mucosal surface, control of bronchial perfusion, triggering of asthma, mucociliary clearance and deposition of inhaled pollutant gases. This work was supported in part by Grant No. HL24163 of the National Institutes of Health.     

The heat stable antigen (CD24) is not required for the generation of CD4+ effector and memory T cells by dendritic cells in vivo

Previous work has established that CD24 is a costimulatory molecule for T-cell clonal expansion. Studies using CD24 -/- mice demonstrated that CD24 plays a critical role in the CD28-independent immune response against virus and soluble antigens. The role of CD24 on dendritic cells (DCs) has not been reported. Here, we compare the CD24(+/+) and CD24(-/-) DCs in the induction of initial clonal expansion and elicitation of memory CD4(+) T cells in vivo. Our results demonstrate that the CD24 expressed on DCs is essential neither for the induction of initial T-cell clonal expansion nor for elicitation of memory activity of primed T cells in vivo.     

Behavioral and autonomic temperature regulation in competition with food intake and water balance of pigeons

Four adult pigeons were conditioned to adjust to a preferred ambient temperature and to receive food or water by instrumental responses. The experiments were performed in a Skinner-box under heat load conditions. Each session lasted 1 h. The birds were deprived of food and water for several days before the actual experiments with the exception of the control tests.The exposure to different heat loads (50°, 55° and 60° C) effected both an increase in the responses for cold reward and a rise in respiratory evaporation (panting). The combined effort of behavioral and autonomous responses resulted in constant body temperature (42° C) under the three heat conditions (Fig. 1).The food deprivation effected a preference of instrumental response for feeding and a negligence of behavioral temperature regulation, whereby a slight hyperthermia resulted in the first part of heat exposure (55° C, Fig. 2).Water deprivation reduced the rate of respiration and simultaneously forced the response for cold reward, through which the deep body temperature was adjusted to the control level of 42° C (Fig. 3).Intragastric infusion of 20 ml NaCl (0.8 mol) half an hour before starting heat load (55° C) produced the same result as water deprivation. Whereas infusion of isoosmotic KCl solution did not produce any deviation from the control tests (Fig. 4).The results show competition between the conditioned thermal behaviour and the motivation of feeding or drinking in animals which may permit to compare the conditioned thermal behaviour with the natural kinds of behavioral temperature regulation. The non-appearance of hyperthermia under conditions of water deprivation and NaCl loading may indicate that the animals are able to use the autonomous and the behavioral types of heat defence responses to a greater or lesser extent as circumstances demand. This question seems to be of great interest and is fully discussed here.     

Angiogenesis but not neurogenesis is critical for normal learning and memory acquisition

Aerobic exercise has been well established to promote enhanced learning and memory in both human and non-human animals. Exercise regimens enhance blood perfusion, neo-vascularization, and neurogenesis in nervous system structures associated with learning and memory. The impact of specific plastic changes to learning and memory performance in exercising animals are not well understood. The current experiment was designed to investigate the contributions of angiogenesis and neurogenesis to learning and memory performance by pharmacologically blocking each process in separate groups of exercising animals prior to visual spatial memory assessment. Results from our experiment indicate that angiogenesis is an important component of learning as animals receiving an angiogenesis inhibitor exhibit retarded Morris water maze (MWM) acquisition. Interestingly, our results also revealed that neurogenesis inhibition improves learning and memory performance in the MWM. Animals that received the neurogenesis inhibitor displayed the best overall MWM performance. These results point to the importance of vascular plasticity in learning and memory function and provide empirical evidence to support the use of manipulations that enhance vascular plasticity to improve cognitive function and protect against natural cognitive decline.     

The association between maternal cocaine use during pregnancy and physiological regulation in 4- to 8-week-old infants: an examination of possible mediators and moderators

OBJECTIVE: To examine the association between maternal cocaine use during pregnancy and physiological measures of regulation, which included heart rate (HR) and respiratory sinus arrhythmia (RSA). METHODS: Potential mediators and moderators of this association were explored. Participants were 141 mother-infant dyads (77 cocaine exposed and 64 nonexposed) recruited at birth. Average infant HR and RSA was assessed at 4-8 weeks of age during a 15 minute period of sleep. RESULTS: Results indicated a dose-dependent effect of prenatal exposure to cocaine on RSA. There was no evidence that fetal growth or other prenatal exposure to substances mediated this association or that fetal growth or maternal age moderated this association. Regression analyses also indicated that birth weight (BW), but not birthlength (BL), head circumference (HC) or other substance use, mediated the association between prenatal exposure to cocaine and heart rate. CONCLUSIONS: These results suggest that cocaine exposure is associated with physiological regulation at 4-8 weeks of age and highlight the importance of considering level of exposure when assessing infant outcomes.     

Biochemical characteristics and water exchange in the surface layer of human joint cartilage

We compared the contents of collagen, glycosaminoglycans, and various forms of water in the surface layer and whole tissue of joint cartilages of different localization. It was found that the surface layer is characterized by reduced content of glycosaminoglycans compared to the whole tissue and higher water-holding capacity due high content of bound water.     

Food and water intake and weight regulation in the pigeon

The interaction of eating and drinking and the relation between intake and body weight was examined in pigeons maintained under laboratory conditions in order to obtain normative data on intake and weight regulation in this species. Under ad lib conditions food and water intake values are correlated, while deprivation of either nutrient leads to a reduction in the intake of the other. A linear relation between the log food intake and the log body weight was found under both ad lib and deprivation conditions. Following a period of food deprivation the pigeon shows both a short-term and a long-term compensatory increase in food intake whose magnitude is directly proportional to the degree of body weight loss produced by deprivation. The findings for the pigeon are similar in many respects to those reported for the rat and are discussed in relation to weight regulation and motivational mechanisms in hunger and thirst.     

Na+-H+ exchange is not important for pancreatic HCO-3 secretion in the pig

Veel , T., Villanger , O., Holthe , M.R., Cragoe jr ., E.J. & Reder , M.G. 1992. Na⁺-H exchange is not important for pancreatic HCO^-₃ secretion in the pig. Acta Physiol Scand 144 , 239–246. Received 13 September 1991, accepted 14 November 1991. ISSN 0001–6772. University of Oslo, Institute for Experimental Medical Research and Surgical Department, Ullevaal Hospital, Oslo, Norway. Pancreatic inter- and intralobular duct cells extrude H⁺-ions to interstitial fluid when they secrete HCO^-₃ to pancreatic juice. This study assesses the potential importance of Na⁺-H⁺-ion exchange for H⁺-ion extrusion and secretion of HCO^-₃ using the Na⁺-H⁺ exchange blockers amiloride and hexamethylene-amiloride. Intracellular pH (pH,) in inter- and intralobular pancreatic duct epithelium was measured using BCECF fluorescence. H⁺-ion efflux was measured using a NH₄Cl prepulse, acid-loading technique. In HCO^-₃-free media, pH₁ recovery following acid loading was blocked by amiloride (10^-4 m) and hexamethylene-amiloride (10^-6 m) , demonstrating amiloride-and hexamethylene-amiloride-sensitive Na⁺-H⁺ exchange. However, 5 × 10^-6 M hexamethylene-amiloride did not reduce secretin-dependent pancreatic HCO, secretion in vivo. Maximal H⁺-efflux through Na⁺-H⁺ exchange was 1.5 ± 0.2μmol min^-1 ml cell volume^-l, i.e. less than 1 % of estimated net H⁺-ion efflux during HCO^-₃ secretion. Conclusion: amiloride- and hexamethylene amiloride sensitive Na⁺-H⁺ exchange is not important for secretin-dependent pancreatic HCO^-₃ secretion in the pig. Other mechanisms for H⁺ extrusion dominate.     

DFNB49 is an important cause of non-syndromic deafness in Czech Roma patients but not in the general Czech population

?afka Bro?ková D, La?t?vková J, ?těpánková H, Kr?tová M, Trková M, My?ka P, Seeman P. DFNB49 is an important cause of non-syndromic deafness in Czech Roma patients but not in the general Czech population. Due to endogamy, the Roma have a higher risk for autosomal recessive (AR) disorders. We used homozygosity mapping on single-nucleotide polymorphism chips in one Czech Roma consanguineous family with non-syndromic hearing loss (NSHL). The second largest homozygous region in a deaf patient was mapped to the previously reported DFNB49 region. The MARVELD2 gene was recently reported as a causal gene for NSHL DFNB49. Sequencing of the MARVELD2 gene revealed a previously reported homozygous mutation c.1331+2 T>C (IVS4 + 2 T>C) in the deaf child. Subsequently, the same mutation was found in two more Roma families from an additional 19 unrelated Czech Roma patients with deafness tested for the MARVELD2 gene. To explore the importance of MARVELD2 mutations and DFNB49 for the general Czech and Central European population with early hearing loss we also tested 40 unrelated Czech patients with AR NSHL. No pathogenic mutation in the MARVELD2 gene was found in a group of 40 Czech non-Roma patients. Mutations in the MARVELD2 gene seem to be a significant cause of early NSHL in Czech Roma and this gene should be tested in this group of patients after GJB2.     

犬急性肺损伤早期不同通气策略对气体交换和血管外肺水的影响

目的: 探讨急性肺损伤(ALI)早期应用控制性高浓度氧疗、持续气道内正压(CPAP)和双水平气道内正压(BiPAP)不同通气策略对气体交换和血管外肺水的影响。方法: 24只杂种犬在制作油酸ALI模型成功后(PaO₂/FiO₂≤300 mmHg),保持自主呼吸,随机分为:(1)控制性高浓度氧疗组(n=8);(2)CPAP组(n=8);(3)BiPAP组(n=8)。连续记录并计算正常、ALI早期(阳性对照)和干预后1~4 h内各项气体交换和血流动力学指标。结果: 在氧合指数(PaO₂/FiO₂)的改善上,干预后4 h BiPAP组效果最明显(375.83±81.55, P<0.01),其次是CPAP组(327.17±78.82, P<0.01),氧疗组改善不显著(255.00±49.85, P>0.05)。在肺泡死腔与潮气容积之比值[V_D(alv)/V_T]上,氧疗组进一步增大(P<0.01),CPAP组和BiPAP组显著降低(P<0.01)。3种通气策略均可提高氧输送量(DO₂),BiPAP组效果最明显(P<0.01),其次是CPAP组和氧疗组。氧疗组的氧耗量(VO₂)显著增高,氧摄取率(O₂ER)明显高于CPAP组和BiPAP组(P<0.05, P<0.01)。干预后3组肺泡气-动脉血氧分压差[P_(A-a)O₂]较正常基础值和ALI早期均显著增高(P<0.01),3组间两两比较无显著差异(P>0.05)。在肺内分流比例(Qs/Qt)上,BiPAP组改善最明显(P<0.01),其次是CPAP组(P<0.01),氧疗组效果不显著。3组实验动物的肺动脉楔压(PAWP)和心排指数(CI)保持相对稳定。在平均肺动脉压(MPAP)和肺循环阻力指数(PVRI)上CPAP组和BiPAP组均进一步增高(P<0.05, P<0.01)。3组对血管外肺水指数(ELWI)的改善无显著作用(P>0.05)。结论: 在ALI早期,BiPAP和CPAP对于改善气体交换和组织氧合具有积极作用,其中BiPAP效果更为显著。3种通气策略对血管外肺水的改善无显著作用。     

Presence of interstereocilial links in waltzer mutants suggests Cdh23 is not essential for tip link formation

Cadherin23 has been proposed to form the upper part of the tip link, an interstereocilial link believed to control opening of transducer channels of sensory hair cells. However, we detect tip link-like links in mouse mutants with null alleles of Cdh23, suggesting the presence of other components that permit formation of a link between the tip of one stereocilium and the side of the adjacent taller stereocilium.     

Genetic evidence that action of cAMP-dependent protein kinase is not an obligatory step for antiviral and antiproliferative effects of human interferon in Chinese hamster ovary cells

Several Chinese hamster ovary (CHO) cell mutants with altered cAMP-dependent protein kinases were utilized to study the possible involvement of this enzyme in mediating interferon effects in cultured cells. Human fibroblast interferon had a pronounced protective effect for CHO cells against encephalomyocarditis virus (EMCV). This protective effect was also observed in cAMP-resistant CHO mutants with protein kinase defects, although to a slightly lesser extent. EMCV, however, which grows well in wild-type CHO cells, grew poorly in the cAMP-resistant CHO mutants even in the absence of interferon, suggesting that cAMP-dependent protein kinase is involved in the normal growth of this virus. The growth inhibitory and morphological effects of human fibroblast interferon on CHO cells as well as the induction of 2',5'-oligoA synthetase and the level of RNase F activity (which is constitutive in CHO cells) were very similar in wild-type and mutant CHO cells. It is concluded from these studies that cAMP-dependent protein kinase may have a facilitating role in antiviral activity of interferon, but does not have an obligatory role in mediating either the antiviral or antiproliferative effects of interferon in CHO cells.     

Reciprocal mitotic recombination is the predominant mechanism for the loss of a heterozygous gene in saccharomyces cerevisiae

The loss of a functional copy of a heterozygous tumor suppressor gene represents an important step during neoplastic transformation. In order to learn more about the genetic events that lead to spontaneous and drug-induced loss of heterozygosity, a diploid Saccharomyces cerevisiae strain was constructed that allows the detection of the loss of a heterozygous gene by means of direct selection. The strain contains a single functional URA3 gene copy inserted at the ADE2 locus located on the right arm of chromosome 15. In addition, the chromosome contains two other phenotypic marker genes, HIS3 which is located distal from URA3, and PHO80 which is closely linked to the centromere. The homologous chromosome lacks all three marker genes. Loss of the heterozygous copy of URA3 can easily be detected by 5-fluoro-orotic acid resistance of the resulting clones. Simple phenotypic tests of the resistant clones further allows one to distinguish whether the loss of the URA3 gene copy occurred by crossing over, chromosomal loss, or point mutation and gene conversion. Loss of heterozygosity was found to be induced in a dose-dependent fashion by UV radiation and by several chemical agents. All the tested mutagens induced loss of heterozygosity predominantly by crossing over. © 1994 Wiley-Liss, Inc.