Oxytocin Messenger Ribonucleic Acid Levels in the Medial Preoptic Area are Increased During Lactation

The peptide hormone oxytocin has an important role in parturition, lactation and maternal behavior. The present study employed in situ hybridization histochemistry to determine whether oxytocin messenger ribonucleic acid (mRNA) levels in cells in the medial preoptic area, a brain area known to control maternal behavior, change during pregnancy and lactation in the rat. Female rats were perfused on either Day 18 or 22 of pregnancy or Day 5 of lactation. Ovariectomized female rats were included as an additional control group. Cells expressing oxytocin mRNA were detected by in situ hybridization using an [¹²⁵ l]-labeled 38 base synthetic oligodeoxynucleotide probe complementary to the C-terminal coding region of the preprooxytocin. Relative differences in oxytocin mRNA levels were determined by silver grain counting of labeled cells. A group of oxytocin neurons in the dorsal medial preoptic area, called the lateral subcommissural nucleus, showed elevated oxytocin mRNA levels in lactating animals relative to ail other groups. Oxytocin mRNA levels in the neurons of the periventricular nucleus of the preoptic area did not change across pregnancy and lactation. This result extends the findings of others showing elevated oxytocin mRNA levels in magnocellular nuclei of lactating animals. The results are discussed in terms of the possible role of oxytocin cells in the medial preoptic area in the expression of maternal behavior.     

Activity of monoamine oxidase in the medial preoptic area and median eminence of female rats of different ages

Total monoamine oxidase activity in the medial preoptic area and median eminence (with surrounding tissue) has been studied in female rats of three age groups, viz., those aged 1.5–2 months (peripubertal), 4–5 months (mature), and over 12 months (aging). Monoamine oxidase activity was measured using kynuramine as a substrate and changes in the concentration of product (4-hydroxyquinoline) were recorded at 327 nm. In the medial preoptic area, the lowest activity (nmole kynuramine/min/mg protein, M ± m) was found during the peripubertal period (1.55 ± 0.11), while in mature and aging rats the activities were similar (1.93 ± 0.12 and 2.01 ± 0.15, respectively). In the median eminence, the greatest activity of monoamine oxidase was found in the aging rats (6.61± 0.56), whereas in the rats of peripubertal and mature age the activities were similar (4.79 ± 0.57 and 4.36 ± 0.25, respectively). In animals aged 4–5 months, we found a tendency toward a negative correlation between the activity of monoamine oxidase in the medial preoptic area and the activity in the median eminence. Our results suggest that opposing changes in enzyme activity are necessary for the coordinated work of the monoaminergic systems in the areas studied.     

Opioid receptor subtypes associated with ventral tegmental facilitation and periaqueductal gray inhibition of feeding

Eating was induced in sated animals by lateral hypothalamic electrical stimulation following central microinjections of mu- (morphine), delta-([D-Pen2,D-Pen5]enkephalin) or kappa-(U-50,488H) receptor agonists, or saline. With stimulation intensity fixed at a moderate level, time to eat 3 45-mg food pellets decreased with increases in stimulation frequency, approaching an asymptote near 7 s at ca. 70 Hz. Ventral tegmental injections (8 but not 0.8 nmol) of each of the 3 drugs reduced the minimum frequency required to produce eating of 3 pellets within 20 s and reduced the frequency at which asymptotic performance was produced; the drugs were equally effective at these doses. Naloxone (2 mg/kg) reversed the effects of each drug; naloxone was slightly more effective against morphine than against DPDPE or U-50,488H. These data suggest that all 3 receptor classes may contribute to the ventral tegmental facilitation of feeding. Periaqueductal gray injections (16 but not 1.6 nmol) of morphine had the opposite effect; they increased the stimulation frequency required to cause eating of 3 pellets in 20 s, and decreased the speed of eating across all stimulation frequencies. Periaqueductal gray injections of the delta- and kappa-agonists were each without effect. These data indicate that the periaqueductal gray inhibition of feeding is mediated solely by mu-receptors and their associated periaqueductal gray circuitry.     

Evidence for a morphologically distinct subpopulation of striatipetal axons following injections of WGA-HRP into the ventral tegmental area in the rat

Following injections of small volumes (10-30 nl) of WGA-HRP (1-2%) into the ventral tegmental area, axonal transport of the lectin-peroxidase conjugate to ventral striatum was evaluated by light microscopy after TMB histochemistry and by electron microscopy following stabilization of the TMB reaction product with DAB and H2O2. Label was distributed more or less evenly in ventral striatum, with only slight patchiness observable in the boundary zone between the nucleus accumbens and ventromedial caudate-putamen. The electron microscope revealed that labeled axons contained markedly flattened vesicles and dense axoplasm and contacted perikarya, dendrites and dendritic spines of short (0.2-0.3 microns) symmetric appositions. Boutons with a similar triad of morphological features were observed in preparations processed for conventional electron microscopy and for tyrosine hydroxylase immunocytochemistry, suggesting that the characteristic morphological features observed are not an epiphenomenon related to histochemical processing.     

家兔大鼠延髓呼吸中枢压力感受区的细胞构筑

24只家兔和10只大鼠的延髓呼吸中枢压力感受区(BSA),经HE、Cajal等染色及免疫组化技术作细胞构筑学研究。BSA在软脑膜2～82μm之下,范围为390μm×490μm×1000μm,由中、小型多极和梭形神经元构成,属B1/35-羟色胺能神经元。其表层的胶质纤维及神经纤维与脑表面平行呈板层状排列。BSA富于毛细血管。     

THE EFFECTS OF 4-METHYL-2-THIOURACIL ON FIBRE TYPE AND CROSS-SECTIONAL AREA IN THE SOLEUS MUSCLE OF THE RAT

The effects of 4-methyl-2-thiouracil (MTU, 0.1% in drinking water) on the composition and cross-sectional area of muscle fibres of the rat soleus muscle were studied. The percentage of fast twitch-oxidative-glycolytic (FOG) fibres fell after 2 weeks of treatment with MTU to zero at 8 weeks. In contrast the percentage of FOG fibres in untreated animals fell to 19.2 +/- 2.1% during this period. The mean cross-sectional area of FOG and slow twitch-oxidative (SO) fibres were respectively 39.9% and 23.8% smaller than those of their respective controls 6 weeks after treatment. At 8 weeks the percentage reduction of SO fibre area was 26.8% of the control value. This study indicates that MTU treatment causes atrophy and redistribution of fibre type in the soleus muscle.     

Immunocytochemical localization of aromatase in the brain

An immunocytochemical peroxidase-antiperoxidase procedure using a purified polyclonal antibody raised against human placental aromatase was used to localize aromatase-containing cells in the Japanese quail brain. Immunoreactive cells were found only in the preoptic area and hypothalamus, with a high density of positive cells being present in the sexually dimorphic medial preoptic nucleus, in the ventromedial nucleus of the hypothalamus and in the infundibulum. The positive material was localized in the perikarya and in adjacent cytoplasmic processes. Aromatase-containing cells were a specific marker for the sexually dimorphic preoptic nucleus. Treatment with testosterone produced a 6-fold increase in the aromatase activity of the preoptic area and a 4-fold increase in the number of immunoreactive cells in the medial preoptic nucleus. Thus, the increase in aromatase activity observed after testosterone administration is caused by a change in enzyme concentration.     

地震灾区野战医疗所预防与控制感染的做法和体会

根据“5·12”汶川大地震灾区野战医疗所感染的流行特点，结合野战医疗所在预防和控制感染方面的实践经验，提出以下预防与控制感染的具体措施，即：严格区域划分，准备必要物资，制定相关制度，严格操作规程，加强环节控制，严格垃圾管理，强化人员培训，做好质量监控。实践证明，重视人员培训、强化组织管理和制度落实、加强环节监控是预防和控制感染的有效保证。     

Reticular formation activity during wakefulness and sleep in a hibernator (Spermophilus lateralis)

This study examined ground squirrel reticular formation (RF) cell activity as a function of: (1) arousal state, and, (2) phasic alterations in neck muscle activity. A total of 37 neurons were recorded from 11 behaving squirrels (Spermophilus lateralis). Five cells were located in the midbrain RF, 15 were in the lateral pontine site implicated in inhibition of motor output, i.e. the subcoeruleus area, 11 were in the medial pontine RF, and 6 were in the medullary RF. Regardless of location, the majority of the cells (81%; 30 of 37) exhibited greatest activity when the animals were awake and/or in rapid-eye-movement (REM) sleep. However, the relationship between neuronal activity and phasic alterations in neck muscle activity differed as a function of location. The activity of 53% of cells (8 of 15) located in the subcoeruleus area increased with phasic decreases in electromyographic (EMG) activity, whereas the activity of cells (22 of 22) in other RF sites decreased or did not change with phasic decreases in EMG activity. The increased activity of subcoeruleus area cells during phasic decreases in neck muscle activity is further evidence suggesting that the lateral pontine RF is involved in promotion of muscle atonia during REM sleep and possibly wakefulness.