Autonomic control of heart rate in the neonatal rhesus monkey

Autonomic control of resting heart rate was assessed using atropine and propranolol in 20 neonatal (2 to 3 weeks old) male Rhesus monkeys. After release from restraint for placement of a venous catheter, the average heart rate significantly decreased from 220 +/- 7 beats/min to 181 +/- 6 beats/min within 15 minutes and remained stable for the 2 hours. Autonomic control of resting heart rate is mediated through both divisions of the autonomic nervous system with the sympathetic system having a dominant influence. This is in contrast to the adult Rhesus, where the parasympathetic nervous system controls resting heart rate.     

Presence of Kynurenine Hydroxylase in Developing Rat Brain

Abstract: Kynurenine-3-hydroxylase, an enzyme that is part of the degradative pathway for tryptophan, was present in the cerebral cortex of neonatal rats and exhibited a K_m , for L-kynurenine close to that of the liver enzyme. This enzyme was enriched in mitochondrial fractions isolated from cerebral cortices of neonatal rats by Ficoll-sucrose gradient centrifugation, with some activity also present in synaptosomal fractions probably due to the mitochondrial content of synaptosomes since cytochrome c oxidase, another mitochondrial enzyme, had a similar distribution in the gradient. Kynurenine hydroxylase as well as monoamine oxidase, another mitochondrial enzyme, had increased specific activities in synaptosomal fractions isolated from 14-day-old rats compared to fractions from 8-day-old rats. Hypothyroidism, induced on the day of birth, resulted in increased activities of kynurenine hydroxylase and monoamine oxidase in synaptosomal fractions isolated from 14-day-old rats.     

Prevalence and age at development of enamel hypoplasias in Mexican children

Enamel hypoplasias, deficiencies in enamel thickness resulting from disturbances during the secretory phase of enamel development, are generally believed to result from nonspecific metabolic and nutritional disruptions. However, data are scare on the prevalence and chronological distributions. of hypoplasias in populations experiencing mild to moderate malnutrition. The purpose of this article is to present baseline data on the prevalences and chronological distributions of enamel hypoplasias, by sex and for all deciduous and permanent anterior teeth, in 300 5 to 15-year-old rural Mexican children. Identification of hypoplasias was aided by comparison to a published standard (Federation Dentaire Internationale: Int. Dent. J. 32(2):159-167, 1982). The location of defects, by transverse sixths of tooth crowns, was used to construct distributions of defects by age at development. One or more hypoplasias were detected in 46.7% (95% CI = 40.9-52.5%) of children. Among the unworn and completely erupted teeth, the highest prevalence of defects was found on the permanent maxillary central incisors (44.4% with one or more hypoplasias), followed by the permanent maxillary canine (28.0%) and the remaining permanent teeth (26.2 to 22.2%) Only 6.1% of the completely erupted and unworn deciduous teeth were hypoplastic. The prevalence of enamel defects on the permanent teeth was up to tenfold greater than that found in studies of less marginal populations that used the FDI method. The prevalence of defects in transverse zones suggests a peak frequency of hypoplasias during the second and third years for the permanent teeth, corresponding to the age at weaning in this group. In the deciduous teeth, a smaller peak occurs between 30 and 40 weeks post gestation. The frequency of defects after three years of age is slightly higher in females than males, suggesting a sex difference in access to critical resources.     

Infection of mammalian hosts by milk-borne nematode larvae: A review

Milk-borne or transmammary infection has been observed to occur in several host-parasite systems. In the order of their observation, these are Uncinaria lucasi-fur seal; Strongyloides ransomi-swine; Ancylostoma caninum-dog; Toxocara canis-dog; Strongyloides westeri-horse; Neoascaris vitulorum-cow; Strongyloides papillosus-cow and -sheep; and Toxocara cati-cst. Some of these parasites are largely dependent on milk-borne infection of neonatal animals. All have a tissue migratory phase in their life cycle. Most of these parasites also utilize other modes or combinations of modes in infecting new hosts. The potential importance of milk-borne infection as a factor in human hookworm disease is pointed out as is the need for complete assessment of this avenue of infection.     

Estrogen treatment during development alters adult partner preference and reproductive behavior in female laboratory rats

There is broad acceptance for the idea that during development estradiol ‘organizes’ many aspects of reproductive behavior including partner preferences in the laboratory rat. With respect to partner preference, this idea is drawn from studies where estrogen action was in someway blocked, either through aromatase or estrogen receptor inhibition, during development in male rats. The lack of estrogens neonatally results in a decrease in the male rat's preference for females. In this study, the effect of early postnatal estradiol treatment on the partner preferences of female rats was examined as a further test of the hypothesis that male-typical partner preference is dependent upon early exposure to estrogens. Our principal finding was that increased postnatal estradiol exposure during development affected partner preference in the expected direction, and this effect was seen under several adult hormonal and behavioral testing conditions. Female rats that received exogenous estradiol during development spent more time with an estrous female and less time with a sexually active male than did cholesterol treated females. The estradiol treatment also disrupted normal female sexual behavior, receptivity, and proceptivity.     

Neonatal coagulopathies: A review of established and emerging treatments

Despite the relative frequency of both bleeding and clotting disorders among patients treated in the neonatal intensive care unit, few clear guidelines exist for treatment of neonatal coagulopathies. The study and treatment of neonatal coagulopathies are complicated by the distinct hemostatic balance and clotting components present during this developmental stage as well as the relative scarcity of studies specific to this age group. This mini-review examines the current understanding of neonatal hemostatic balance and treatment of neonatal coagulopathies, with particular emphasis on emerging treatment methods and areas in need of further investigative efforts.     

Activation of PH-domain leucine-rich protein phosphatase 2 (PHLPP2) by agonist stimulation in cardiac myocytes expressing adenylyl cyclase type 6

The Ser/Thr-specific phosphatase PHLPP (pleckstrin homology domain leucine-rich repeat protein phosphatase) regulates the amplitude and duration of agonist-evoked Akt signaling by dephosphorylating the hydrophobic motif (Ser473) of Akt, therefore inactivating Akt. We recently reported that gene transfer of adenylyl cyclase type 6 (AC6) into neonatal rat cardiac myocytes was associated with increased Akt phosphorylation and activity. To determine the underlying mechanisms for AC6-associated increase in Akt activation, we determined how AC6 gene transfer regulated the activity of PHLPP2 (one of the three PHLPP family phosphatases) in neonatal rat cardiac myocytes. We found that increased Akt activity was associated with inhibition of PHLPP2 activity by AC6. AC6 was physically associated with PHLPP2, which prevents PHLPP2-mediated Akt dephosphorylation. However, isoproterenol or forskolin stimulation immediately activated PHLPP2, which resulted in markedly dephosphorylation of Akt at Ser473. Activation of PHLPP2 by isoproterenol and forskolin was cAMP-independent, but required an intact cytoplasmic domain of AC6. Mutation in the cytoplasmic domain of AC6 abolished agonist-induced PHLPP2 activation. This novel bidirectional regulation of Akt activity may contribute to the unexpected favorable effects of AC6 on the failing heart.     

建立新生大鼠吸入麻醉模型及异氟醚对其海马凋亡的影响

目的:建立新生大鼠吸入麻醉模型并探讨吸入麻醉药异氟醚对其海马凋亡的影响。方法:Penlon Prima SP麻醉机、异氟醚挥发罐及自制带进出气口的麻醉小室。共55只7日龄的SD大鼠用于实验。将其中35只大鼠随机分为7组(n=5)。实验组(Ⅰ-Ⅵ组)异氟醚挥发罐刻度分别为0.125%,0.25%,0.5%,1%,1.5%,2%;新生大鼠置于自制密封麻醉小室内,分别通入含上述异氟醚浓度的混合气体。对照组(第Ⅶ组)给予未混合异氟醚的30%的氧气。将小室安放于37℃恒温箱内。调节气体流量2L/min。实验组于通入气体5,10,15,30,90,180,360 min(T1-7)时于小室出口处抽取10mL气体,采用气相色谱法测定麻醉小室内异氟醚浓度。于通入气体360 min(T7)自新生大鼠左心室采血行血气分析;另取SD大鼠20只,随机分为对照组(C组,n=10),1.5%异氟醚组(I组,n=10),按上述方法建立异氟醚吸入麻醉模型,麻醉结束后2h处死大鼠,采用免疫组织化学法观察C组和I组大鼠大脑海马区Active caspase-3的表达。结果:①麻醉小室出口异氟醚浓度(Y)与麻醉机挥发罐异氟醚浓度(X)的直线回归方程为Y=1.5472X-0.0575(r=0.9993)。②血气分析结果显示:Ⅰ-Ⅵ组与Ⅶ组血气分析组间差异无统计学意义(P0.05)。③免疫组化结果显示:与C组相比,I组大鼠海马Active caspase-3明显增加,差异有统计学意义(P0.05)。结论:通过麻醉机、异氟醚挥发罐及自制密封带进出气口的麻醉小室成功建立了新生大鼠异氟醚麻醉模型;为进一步研究异氟醚及相关吸入麻醉药对突触发生期的神经毒性提供了实验基础。