On the mechanism by which dopamine inhibits prolactin release in the anterior pituitary

An $\text{in}$$\text{vitro}$ perfusion system was used to assess the effects of chloride channel blockers, dopamine (DA) receptor agonists and antagonists, and GABA receptor agonists and antagonists on prolactin release from the mouse anterior pituitary. Dopamine and muscimol inhibited prolactin release ($\text{IC}{}_{50}{}^1\text{= 6 × 10}{}^{\mathrm{?8}}\text{M and}\text{10}{}^{\mathrm{?5}}\text{M}$ respectively). The GABA receptor antagonist bicuculline blocked the inhibition of prolactin release by muscimol but not dopamine. The dopamine receptor antagonist chlorpromazine blocked the dopamine- but not muscimol-induced inhibition of prolactin release. Haloperidol, however, reversed both the muscimol and dopamine induced inhibition of prolactin release. Furthermore, the chloride channel blocker picrotoxinin blocked the inhibition of prolactin release elicited by both dopamine and muscimol. These later results suggest that the anterior pituitary dopamine receptor which mediates the inhibition of prolactin release may be coupled to a picrotoxinin sensitive chloride ionophore and that haloperidol may affect the function of both DA and GABA receptors in the anterior pituitary.     

Environmental Particulate (PM2.5) Augments Stiffness-Induced Alveolar Epithelial Cell Mechanoactivation of Transforming Growth Factor Beta

Dysfunctional pulmonary homeostasis and repair, including diseases such as pulmonary fibrosis (PF), chronic obstructive pulmonary disease (COPD), and tumorigenesis have been increasing over the past decade, a fact that heavily implicates environmental influences. Several investigations have suggested that in response to increased transforming growth factor - beta (TGFβ) signaling, the alveolar type II (ATII) epithelial cell undergoes phenotypic changes that may contribute to the complex pathobiology of PF. We have previously demonstrated that increased tissue stiffness associated with PF is a potent extracellular matrix (ECM) signal for epithelial cell activation of TGFβ. The work reported here explores the relationship between tissue stiffness and exposure to environmental stimuli in the activation of TGFβ. We hypothesized that exposure of ATII cells to fine particulate matter (PM2.5) will result in enhanced cell contractility, TGFβ activation, and subsequent changes to ATII cell phenotype. ATII cells were cultured on increasingly stiff substrates with or without addition of PM2.5. Exposure to PM2.5 resulted in increased activation of TGFβ, increased cell contractility, and elongation of ATII cells. Most notably, on 8 kPa substrates, a stiffness greater than normal but less than established fibrotic lung, addition of PM2.5 resulted in increased cortical cell stiffness, enhanced actin staining and cell elongation; a result not seen in the absence of PM2.5. Our work suggests that PM2.5 exposure additionally enhances the existing interaction between ECM stiffness and TGFβ that has been previously reported. Furthermore, we show that this additional enhancement is likely a consequence of intracellular reactive oxygen species (ROS) leading to increased TGFβ signaling events. These results highlight the importance of both the micromechanical and biochemical environment in lung disease initiation and suggest that individuals in early stages of lung remodeling during fibrosis may be more susceptible than healthy individuals when exposed to environmental injury adjuvants.     

Absence of subtransition in racemic dipalmitoylphosphatidylcholine vesicles

dl-Dipalmitoylphosphatidylcholine multilamellar vesicle suspensions were examined by the method of differential scanning calorimetry. A lack of the subtransition at 18°C was established. Such a subtransition is characteristic for l-dipalmitoylphosphatidylcholine suspensions. This lack is supposed to be the result of the impossibility of the racemic phospholipid mixture to form the low-temperature crystal structure L_c.     

Regulation of mental states and biofeedback techniques: Effects on breathing pattern

The purpose of the present study was to examine whether breathing pattern may be used as a reliable index for the effectiveness of techniques applied for the regulation of mental states. Heart rate (HR), breathing pattern, galvanic skin response (GSR), and electromyogram (EMG) of the frontalis muscle were measured in 39 male and female subjects aged 18–25 years during 10-minute treatment with relaxation technique (autogenic training and/or music) followed by 10 minutes of imagery training. In the first 7 sessions biofeedback (BFB) was not included, while during the last 6 sessions BFB was introduced and utilized by the subjects. Relaxation (music or autogenic training) led to a decrease in breathing frequency, attributed to lengthening of expiration time, as well as reduced HR, GSR, and frontalis EMG response. In most instances imagery training was related to an increase in these indices. Specifically, significant tachypnea was observed during imagery of sprint running. In most cases BFB substantially augmented the physiological responses. In conclusion, our data suggest that, compared with HR, GSR, and EMG responses, the breathing pattern is at least as sensitive to the mental techniques employed, and may be useful as a psychophysiological index for diagnosis and testing, especially in sport practice.     

Distribution patterns of some subterranean Crustacea in the territory of the former Yugoslavia

A selection of the most representative distribution patterns of stygobiont animals is presented. The range of a genus may extend beyond the Dinaride karst, while some species exhibit a holo-Dinaric distribution. The mero-Dinaric distribution is organised in two vicarious centres (in the NW and SE) as well as an epilittoral and a paralittoral belt. The paralittoral distribution is a result of paleogeographic rather than present-day ecological conditions. Important differences between the interstitial faunas of Slovenia (and NE Italy) and Macedonia are probably the result of their different sources. Some other distribution patterns are discussed or summarized from the existing literature. The distribution patterns of this stygobiont fauna are extremely diverse, and are influenced by the geological complexity of the territory as well as by the richness of the fauna concerned. New distribution data for some Copepoda, Thermosbaenacea, and Amphipoda are appended.     

Energetic costs of raising Pygoscelid penguin chicks

Energy requirements of resting Adélie (Pygoscelis adeliae), Gentoo (P. papua) and Chinstrap (P. antarcticd) penguin chicks were determined with respect to body mass via respirometry in Antarctica. Resting metabolic rates of all Pygoscelid penguin chicks were similar (ANOVA p=0.91) and best described by E=0.0096 M^0.98 (n=24, r²=0.97), where E is power (W) and M is mass (g). Using the results obtained here and data published in the literature, I determined a) the amount of food needed from hatching to fledging as 29.8, 31.7 and 56.4 kg per chick for Adélie, Chinstrap and Gentoo penguins, respectively and b) the average amount of food left daily to the parent after feeding the brood throughout the breeding period. Parents keep only a minimum of food for themselves just prior to the time when chicks begin forming crèches. Thereafter, nest relief intervals are increased, and the amount of food parents can keep for themselves rises. The results of both models are discussed with respect to available data on Pygoscelid penguin food requirements.     

Genetics of sex determination in flowering plants

Most flowering plant species are hermaphroditic, but a small number of species in most plant families are unisexual (i.e., an individ-ual will produce only male or female gametes). Because species with unisexual flowers have evolved repeatedly from hermaphroditic progenitors, the mechanisms controlling sex determination in flowering plants are extremely diverse. Sex is most strongly determined by genotype in all species but the mechanisms range from a single controlling locus to sex chromosomes bearing several linked locirequired for sex determination. Plant hormones also influence sex expression with variable effects from species to species. Here, we review the genetic control of sex determination from a number of plant species to illustrate the variety of extant mechanisms. We emphasize species that are now used as models to investigate the molecular biology of sex determination. We also present our own investigations of the structure of plant sex chromosomes of white campion (Silene latifolia - Melan-drium album). The cytogenetic basis of sex determination in white campion is similar to mammals in that it has a male-specific Y-chromosome that carries dominant male determining genes. If one copy of this chromosome is in the genome, the plant is male. Otherwise it is female. Like mammalian Y-chromosomes, the white campion Y-chromosome is rich in repetitive DNA. We isolated repetitive sequences from microdissected Y-chromosomes of white campion to study the distribution of homologous repeated sequences on the Y-chromosome and the other chromosomes. We found the Y to be especially rich in repetitive sequences that were generally dispersed over all the white campion chromosomes. Despite its repetitive character, the Y-chromosome is mainly euchromatic. This may be due to the relatively recent evolution of the white campion sex chromosomes compared to the sex chromosomes of animals. © 1994 Wiley-Liss, Inc.     

Effect of oxygen abstraction on the peroxidase–luminol–perborate system: Relevance to the HRP enhanced chemiluminescence mechanism

Abstraction of oxygen from the HRP enhanced chemiluminescence system has no significant effect on the chemiluminescence generated. It is, therefore, proposed that in the peroxidase-luminol-perborate system at pH 7.3, chemiluminescence is generated by a direct reaction of diazaquinones with hydrogen peroxide and not, as generally assumed, from the reaction of luminol radicals with the molecular oxygen.