Effects of veratridine, tetrodotoxin and other drugs that alter electrical behaviour on secretion of melanocyte-stimulating hormone from melanotrophs of the pituitary pars intermedia

Since melanotrophs are electrically active and exhibit spontaneous Na spikes, a study was made of the effects, on melanotroph secretion, of drugs known to influence electrical properties. The output of melanocyte-stimulating hormone was measured from perifused neurointermediate lobes of mice or melanotrophs dispersed from such lobes of mice or rats. Veratridine (200 microM), which is known to increase Na permeability in a variety of cells, caused a large, although transient, increase in secretion from the melanotrophs that required extracellular Ca2+ and was blocked by the Na-channel blocker tetrodotoxin (1 microM). Tetraethylammonium (10 mM), which blocks K channels and thus prolongs the duration of the action potential in many cells, also stimulated secretion in the melanotrophs in a Ca-dependent manner. This response was not, however, blocked by tetrodotoxin, and is thus not attributable to prolongation of Na spikes in these cells. Moreover, tetrodotoxin did not inhibit basal secretion. The stimulant effect of veratridine on secretion in melanotrophs and its suppression by tetrodotoxin suggests that voltage-dependent Na channels can participate in the regulation of hormone output in these cells of the pituitary pars intermedia. However, the apparent lack of effect of tetrodotoxin on basal secretion suggests that the spontaneous Na spikes previously observed in these cells are not required for promoting the Ca influx which other evidence shows is important for basal secretion.     

Specific immunoglobulin measurements related to exposure and resistance to Schistosoma mansoni infection in Sudanese canal cleaners

The present work comprises a longitudinal study of Schistosoma mansoni infection in occupationally hyper-exposed canal cleaners in the Sudan and the influence of chemotherapy on humoral immune parameters. The study groups included chronically infected canal cleaners (n = 19), newly recruited canal cleaners (n = 17), normally exposed adults (n = 31), school children (n = 46) and Sudanese negative controls (n = 48). Previous studies of the same canal cleaners have demonstrated that chronically infected canal cleaners were more resistant to reinfection than newly recruited canal cleaners. ELISA was used to detect specific IgE and IgG subclasses in response to whole worm antigen (WWH) and soluble egg antigen (SEA) before and 3 months after praziquantel treatment in the groups of canal cleaners and before and 1 year after treatment in normally exposed adults. When intensity of infection was correlated with IgE antibody response, the resistant group of canal cleaners (those who stopped passing ova after treatment) showed a significant positive correlation between intensity of infection and specific IgE to WWH (Spearman''s correlation coefficient = 0·49, P < 0·05) compared with a highly significant negative correlation in the susceptible group (acquired new infection after treatment, Spearman''s correlation coefficient = 0·94, P < 0·01). Normally exposed adults and school children had significantly less specific IgE to WWH than canal cleaners, while chronically infected canal cleaners had significantly higher levels of specific IgG1 to WWH than newly recruited canal cleaners and school children, and significantly higher levels of specific IgG4 to WWH than school children. There was a significant increase in specific IgG1 and IgG4 to WWH, 3 months after treatment, in newly recruited canal cleaners and a significant decrease, 1 year after treatment, in normally exposed adults. None of the groups studied after treatment showed a significant change in their specific IgE to WWH. Normally exposed adults had significantly lower levels of specific IgE to SEA than newly recruited canal cleaners, and significantly lower levels of specific IgG1 to SEA than other infected groups. Both newly recruited canal cleaners and school children had significantly higher levels of specific IgG2 to SEA than persons in other groups. Only small differences between groups were observed with regard to specific IgG3 and IgM to SEA. Specific IgG4 to WWH and SEA showed different patterns after treatment between the resistant and susceptible groups of canal cleaners. The resistant group maintained the same level of IgG4 to WWH after treatment compared with a significant increase in the susceptible group. On the other hand, levels of specific IgG4 to SEA showed a highly significant decrease after treatment in the resistant group. In contrast, the same antibody subclass increased after treatment in the susceptible group. Generally, results show an association between IgE and IgG1 responses to WWH and resistance to reinfection. In contrast, an association was observed between IgG2 and IgM responses to SEA and susceptibility to reinfection.     

Membrane properties of rat locus coeruleus neurones

Intracellular recordings were made from neurones in the locus coeruleus contained within a slice cut from rat pons and maintained in vitro. Most neurones fired action potentials spontaneously at frequencies of between 1 and 5 Hz; this did not arise from spontaneous synaptic input but appeared to result from endogenous properties of the membrane conductances. Under voltage clamp at potentials near threshold for action potential generation (? 55 mV) there was a persistent inward calcium current. This current became less with membrane hyperpolarization and was abolished at about ?70 mV. Two potassium currents were observed. The first had properties similar to that generally described as the “fast” potassium current (I_K,A); it flowed transiently (for about 200 ms) when the membrane potential passed from about ?65 to ?45 mV, and was blocked by 4-aminopyridine. The second was a calcium-activated potassium current (I_K,Ca); it flowed for several seconds following a burst of calcium action potentials. Spontaneous and evoked action potentials had both tetrodotoxin-sensitive and tetrodotoxin-resistant components. The latter was apparently due to calcium entry. The potential changes occurring during the spontaneous firing of locus coeruleus neurones could be reconstructed qualitatively from the ionic conductances observed. The membrane properties of the locus coeruleus neurones were remarkably uniform; however, about 5% of cells impaled within the region of the locus coeruleus were electrophysiologically distinct. These atypical cells had short duration action potentials, did not fire spontaneously and had large spontaneous depolarizing synaptic potentials.     

Electrical behaviour in a line of anterior pituitary cells (GH cells) and the influence of the hypothalamic peptide, thyrotrophin releasing factor

Anterior pituitary cells of the GH line, which secrete prolactin spontaneously, showed spontaneous action potential activity. Thyrotrophin releasing factor, which increases secretion in these cells, caused a prompt increase of action potential frequency. Potassium, another secretagogue, depolarized the cells and sometimes initiated a burst of action potentials at the onset of this effect. The action potentials persisted in tetrodotoxin-containing and Na-free media, but were suppressed by the Ca-channel blocker, methoxyverapamil. Moreover, elevating the extracellular Ca²⁺ concentration increased the amplitude of the action potentials. These action potentials therefore have a prominent Ca component. This endows them with a particular interest since secretory activity of these cells is known to be dependent on extracellular Ca²⁺. Ba²⁺, which can substitute for Ca²⁺ in maintaining secretion, also substituted for Ca²⁺ in the maintenance of the action potentials. In addition, Ba²⁺ prolonged action potentials remarkably: tetraethylammonium was less effective in this regard.The several parallels between known secretory behaviour and electrical phenomena encourage the view that analysis of electrical activity in anterior pituitary cells may provide useful clues to events involved in stimulus-secretion coupling and in the secretory control exerted by the brain.     

Different ion channel mechanisms between low concentrations of capsaicin and high concentrations of capsaicin and nicotine regarding peptide release from pulmonary afferents

Vagal nerve stimulation (1 Hz for 1 min), capsaicin (10^-8 M and 10^-6 M), resiniferatoxin (3 × 10^-10 M) and nicotine (10^-4 M) evoked a non-cholinergic bronchoconstriction in the isolated perfused guinea-pig lung preparation. Simultaneously there was an increase in the perfusate levels of calcitonin gene-related peptide-like immunoreactivity, suggesting release from sensory nerves. Both the bronchoconstriction and peptide release evoked by a low concentration of capsaicin (10^-8 M) and that evoked by nerve stimulation were depressed by tetrodotoxin, suggesting involvement of Na⁺ channel dependent depolarization. Since the effects of capsaicin (10^-8 M) and vagal nerve stimulation were inhibited by ω-conotoxin but not influenced by nifedipine, the Ca²⁺-channel involved is probably of N-type. Furthermore, the capsaicin analogue resiniferatoxin also evoked ω-conotoxin sensitive peptide release and bronchoconstriction. At the higher capsaicin concentration (10^-6 M), the functional response was only slightly inhibited by wconotoxin or tetrodotoxin indicating that capsaicin at this concentration evoked peptide release and functional effects through other mechanisms, probably involving Ca²⁺ fluxes in the non-selective cation channel associated with the proposed capsaicin receptor. The nicotine (10^-4 M) evoked peptide release and bronchoconstriction were only marginally influenced by ω-conotoxin or tetrodotoxin. It is concluded that the ion-channel mechanisms underlying the peptide releasing properties of antidromic nerve stimulation and low concentrations of capsaicin are similar and depend on action potential propagation, whereas capsaicin in high, toxic concentration and nicotine mainly act via receptor operated channels.     

Release of endogenous 5-hydroxytryptamine from the neural and the intermediate lobe of the rat pituitary gland evoked by electrical stimulation of the pituitary stalk

A calcium-dependent release of 5-hydroxytryptamine from the neural and intermediate lobe of the rat pituitary gland has been demonstrated following electrical stimulation of the pituitary stalk with stimulation parameters thought to evoke propagated action potentials. The 5-hydroxytryptamine release from the intermediate lobe was double that from the neural lobe. The mass of the intermediate lobe of the rat is about 80% of that of the neural lobe [Holzbauer, Racké, Mann, Cooper, Cohen, Krause and Sharman (1984) J. Neural Transm. 59, 91-104]. The relatively high overflow of 5-hydroxytryptamine from the intermediate lobe agrees with immunohistochemical studies in which a larger number of 5-hydroxytryptamine fibres were seen in the intermediate lobe than in the neural lobe. The present results have demonstrated that the rat hypophysis contains neuronal 5-hydroxytryptamine. They also suggest that this amine may act as a neurotransmitter substance in the neural and intermediate lobe.     

Agreement between CBNAAT,liquid culture and line probe assay for detection of Mycobacterium tuberculosis and anti-tubercular drug resistance in extrapulmonary samples

PurposeCartridge based nucleic acid amplification test (CBNAAT) has been endorsed by the WHO as the screening test for diagnosing extrapulmonary tuberculosis (EPTB). In the present study we report the agreement between CBNAAT (Xpert MTB/RIF), liquid culture (LC) and line probe assay (LPA) for diagnosis of Mycobacterium tuberculosis and detection of drug resistance among EPTB cases.MethodsThe EP samples were subjected to CBNAAT (Xpert MTB/RIF, Cepheid, USA) and wherever possible, to LC (MGIT 960, Becton Dickinson, USA) followed sequentially by first line and second line-LPA (FL-LPA, SL-LPA, Hain Lifescience, Germany) on the isolates.ResultsTotal 566/4080 (13.9%) EP samples were detected positive for M. tuberculosis on CBNAAT. Aspirates from lymph nodes were most often positive (11/30; 36.6%), followed by pus (240/873; 27.5%) and CSF samples (166/104; 15.8%). The detection of M. tuberculosis was more in adults than children except in tissue biopsy samples. Rifampicin resistance was also higher among adults except CSF in which resistance was more in children. Total 185 of 566 (32.7%) CBNAAT positive and 770 of 3510 (21.9%) CBNAAT negative samples could be cultured of which 110/185 (59.4%) and 33/770 (4.3%) respectively turned positive. FL-LPA and SL-LPA of 143 culture isolates showed that 27 isolates had drug resistance, of which 3 (2.1%) were XDR, 11 (7.7%) were Pre-XDR (FQ) and 13 (9.1%) were MDR. Of these 27 resistant isolates, 12 were negative by CBNAAT and two were mislabeled as Rifampicin sensitive or indeterminate based on the unique RpoB gene mutation patterns on LPA. The positive and negative agreements between LC and CBNAAT for detection of M. tuberculosis were 67.1% and 92.7% respectively and between LPA and CBNAAT for rifampicin resistance detection were 98.9% and 92.9% respectively.ConclusionsFor EPTB, CBNAAT should be accompanied with LC wherever possible irrespective of the CBNAAT result.     

肺耐药蛋白在子宫内膜癌中表达及其临床意义

目的 探讨肺耐药蛋白(LRP)在子宫内膜癌治疗中的作用及预后关系。方法 采用免疫组化染色SP法，检测30例石蜡包埋的子宫内膜癌中LRP的表达，并对应用化疗后的效果进行分析。结果 (1)LRP阳性表达率80％(24／30)；(2)LRP表达阳性者的化疗有效率约为45．8％，明显低于LRP表达阴性者(83．3％)；(3)LRP的表达与腹水相关，与患者年龄、临床分期、组织分级无关；(4)LRP表达阴性患者预后明显优于阳性。结论 LRP是评价子宫内膜癌化疗耐药性和预后可靠指标。     

Evaluation of an Ileorectostomised Rat Model for Resistant Starch Determination

The human ileostomy model, widely considered the benchmark for determining in vivo starch digestibility, has disadvantages. The ileorectostomised rat model (IRM) is a possible surrogate but evidence as to its validity is scant. In this preliminary study, the resistant starch (RS) content of test breads made from refined low (LAW-R) and high amylose wheat (HAW-R) flours was established in a randomised cross-over trial involving six human ileostomy participants. Starch digestibility of refined breads and diets made from these flours was then evaluated in ileorectostomised rats using a similar experimental format. Physical performance measures and other data were also collected for the rat model. The amount of RS in the low- and high-amylose breads as measured using the human model was 0.8 ± 0.1 and 6.5 ± 0.3 g/100 g, respectively. The RS level of HAW-R bread determined using ileorectostomised rats was 5.5 ± 0.8 g/100 g, about 15% less than that recorded in the human study, whereas for conventional wheat breads the models produced similar RS values. While offering promise, further validation using a wide variety of starchy food products is needed before the IRM can be considered an acceptable alternative for RS determination.     

The Impact of Diet and Fibre Fractions on Plasma Adipocytokine Levels in Prediabetic Adults

The impact of diet and fibre fractions on adipocytokines in obese subjects with a risk of diabetes has not been investigated in detail yet. The purpose of the study is to evaluate the effects of a 12-month lifestyle intervention with different fibre profiles (resistant starch (RS)—rich fibre, or ordinary food fibre profiles) on adipocytokine levels. Fifty participants are divided into two groups (RS group and Fibre group). The groups differ only in the percentage of the recommended level of the RS consumed as a fraction of the same total fibre amount. The applied dietary intervention includes intake of 7531 KJ/daywith a total fibre portion of 25–35 g/dayfor both groups that includes 15 g/day of RS for the RS group only. The levels of leptin, adiponectin, apelin, resistin, tumor necrosis factor (TNF)-alpha and C-reactive protein (CRP) are measured, and their relationship to anthropometric and biochemical parameters is estimated. Along with significant body weight loss, only leptin is significantly reduced by 13% in the RS group while in the Fibre group, apelin levels are significant (−21%). Polynomial regression shows a negative correlation between RS intake and adiponectin (R2 = 0.145) and resistin level (R2 = 0.461) in the RS group. This study indicates the possibility that fibre fractions differently influence the outcome of lifestyle interventions, as well as their adipocytokine levels, in obese prediabetic adults.