Secretory granule formation and synthesis pathway of secretory proteins in parotid gland cells

The cytochemical technique for endogenous peroxidase and an immunocytochemical method with protein A-gold were used to investigate the formation of the secretory granule substructure in acinar cells of the gerbil parotid glands in normal conditions and after treatment with the ionophore monensin. In untreated animals and 90 min after treatment with monensin, peroxidase activity was seen in rER, in transport vesicles close to the condensing vacuoles, and in the dense core of condensing vacuoles and secretory granules, whereas the Golgi cisternae remain unreactive. At 45 or 60 min after stimulation with monensin, the condensing vacuoles and the immature granules in the trans Golgi area did not exhibit dense cores and their content appeared similar to the peripheral portion of the mature secretory granules. These observations suggest that, in Mongolian gerbil parotid acinar cells, some substances such as peroxidase may be transported from the rER directly to the condensing vacuoles.

Proadrenomedullin NH2-terminal 20 peptide inhibits the voltage-gated Ca2+ channel current through a pertussis toxin-sensitive G protein in rat pheochromocytoma-derived PC 12 cells

The effect of proadrenomedullin NH2-terminal 20 peptide (PAMP) on the voltage-gated Ca2+ channel current was investigated using the perforated whole-cell clamp technique on NGF-treated PC12 cells. PAMP inhibited the Ba2+ current through N-type Ca2+ channels in a concentration dependent manner. Injection of GDPbetaS into the cell abolished the inhibition while injection of GTPgammaS into the cell made the inhibition irreversible, indicating that the PAMP-induced inhibition of the voltage-gated Ca2+ channel was mediated by a G protein. The inhibition was abolished by pretreating the cells with pertussis toxin, indicating that a pertussis toxin-sensitive G protein was involved in the signal transduction mechanism of PAMP. The present study revealed that the inhibition of catecholamine secretion from sympathetic nerve endings by PAMP could be explained by the inhibition of N-type Ca2+ channels, which was mediated by pertussis toxin-sensitive G protein.

The effects of prolonged treatment with citicoline in temporary experimental focal ischemia

Potential therapeutic effects of cytidine 5-diphosphocholine (citicoline), a key intermediary in the biosynthesis of the membrane phospholipid, phosphatidylcholine, are presumably related to enhanced phospholipid synthesis in the ischemic brain. We evaluated prolonged citicoline treatment in a temporary focal ischemia model. Using the suture occlusion model, we induced 2 hours of temporary ischemia in 30 Sprague-Dawley rats. The rats were randomly and blindly assigned to receive intraperitoneally 500 mg/kg citicoline (HD), 100 mg/kg citicoline (LD) or physiologic saline as the control group once daily for 7 days (n = 10 per group) beginning at the time of reperfusion. Neurological scoring (0-5 scale) was performed daily. After elective sacrifice on day 7, or earlier if death occurred prematurely, the brains underwent 2,3,5-triphenyltetrazolium chloride (TTC) staining for calculation of corrected infarct and edema volume. The mean corrected infarct volume in the HD group was 125 +/- 45.2 mm3 (mean +/- SD), significantly smaller than controls, 243.5 +/- 88.6 mm3 (p < 0.01, Scheffe's-test). The LD group infarct volume was 200.2 +/- 62.8 mm3 (N.S.). The mean amount of brain edema in the HD group was 46.4 +/- 45.6 mm3 was smaller than the controls, 92.3 +/- 54.4 mm3 and the LD group, 84.9 +/- 71.7 mm3 (N.S.). Mortality before day 7 in the HD was 30% while it was 50% in the two other groups. The neurologic score on day 7 was 2.5 +/- 1.8 in the HD group, 3.3 +/- 1.8 in the LD group and 3.4 +/- 1.7 in controls (N.S.). These results demonstrate that extended high dose citicoline treatment significantly reduced infarct volume in this temporary focal ischemia model and that there was a trend toward reducing brain edema and mortality. These effects may be related to membrane stabilization and inhibition of free fatty acid release.

GHRH activates a nonselective cation current in human GH-secreting adenoma cells

Electrophysiological responses induced by human (h) growth hormone-releasing hormone (GHRH) were analyzed using the perforated whole cell clamp technique in human growth hormone (GH)-secreting adenoma cells. Application of hGHRH depolarized the membrane by increasing Na+ conductance. The reversal potential of the hGHRH-induced current was -20 to 0 mV. The channel was permeable to Na+, Li+ and K+ but not to TMA+. These properties were compatible with those of nonselective cation channels. Similar nonselective cation current was activated by 8-bromoadenosine 3',5'-cyclic monophosphate and forskolin, and the activation of the hGHRH-induced current was inhibited by protein kinase A (PKA) inhibitors, (R)-p-adenosine 3',5'-cyclic monophosphate and N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinoleinsulfonamide, and PKA inhibitor peptide PKI-(5-24), indicating that hGHRH-induced current was activated by PKA. Cholera toxin pretreatment eliminated the hGHRH-induced current, suggesting that Gs is involved in the activation of this current. This current became irreversible when the cells were pretreated with okadaic acid, suggesting that the recovery of the hGHRH-induced current was mediated by a serine/threonine protein phosphatase. GHRH-induced GH secretion was inhibited in Na+-free medium, suggesting the importance of the nonselective cation current on hGHRH-induced GH secretion. In human GH-secreting nonadenoma cells, hGHRH increased Na+ conductance, as was the case in GH-secreting adenoma cells.

Dynamic pulmonary SPECT of xenon-133 gas washout

A triple-detector SPECT data acquisition mode of "continuous repetitive rotation acquisition" was applied to dynamic pulmonary SPECT with 133Xe gas.

METHODS

Subjects included 7 healthy volunteers, 22 patients with a space-occupying mass lesion, 22 with obstructive lung disease and 10 with restrictive lung disease. Following rebreathing of 133Xe, equilibrium and washout SPECT images during spontaneous breathing were acquired every 30 sec for 5-7 min. Regional 133Xe washout was assessed by the real half-time (T1/2) and mean transit time (MTT) images.

RESULTS

SPECT and MTT images represented a gravity-induced gradient of ventilation in normal lungs and detailed the distribution of heterogeneous 133Xe washout in patient's lungs with or without abnormalities on chest x-ray CT. The T1/2 (111.4 +/- 26.4 sec) and its coefficient of variation (0.36 +/- 0.13) in obstructive lung diseases were significantly different from those (56.8 +/- 3.9 sec and 0.16 +/- 0.15) in restrictive lung diseases (p < 0.001, p < 0.05, respectively). Comparison of SPECT and planar studies assessed in 19 patients revealed superiority of SPECT in detecting ventilatory abnormalities and a high correlation of T1/2 between the two studies ( r= 0.977, p < 0.001).

CONCLUSION

This modality has excellent potential for elucidating the distribution and nature of ventilatory abnormalities.

In vitro fertilization and microinsemination with round spermatids for propagation of nephrotic genes in mice

The ICGN is an inbred strain of mice with a hereditary nephrotic syndrome of an unknown cause. The disease progresses to renal failure, resulting in the deterioration of the systemic condition and in a drastic reduction of reproductive capacity. The present study was undertaken to determine if in vitro fertilization (IVF) and microinsemination using round spermatids could ameliorate the reduced fertility of ICGN mice. Mature oocytes (9.4 +/- 1.1 per mouse) were obtained from PMSG/hCG-primed females 2 to 5 mo of age. When spermatozoa from males aged 3 to 4 mo was used for IVF, a high fertilization rate (82.6%) was achieved and a high rate of embryos developed into blastocysts (92.6%). When spermatozoa from males aged 5 to 7 mo was used, the rates of fertilization and development to blastocysts were significantly lower (63.9 and 47.1%, respectively; P < 0.001). However, the production rate of offspring after embryo transfer was satisfactory irrespective of the age of males (59.1%). When males older than 9 mo were used, no fertilization was achieved due to the very poor motility of the spermatozoa. Microinsemination techniques with round spermatids (electrofusion and intracytoplasmic injection) resulted in the production of normal offspring from the older males, including one azoospermic case. These findings indicate that a conventional IVF technique and microinsemination using round spermatids can be used for propagating mutant genes which cause poor reproductive ability in mice.

[Attempt of helical CT densitometry for assessing regional pulmonary ventilation]

Pulmonary dynamic CT densitometry during steady-state breathing was recorded and analyzed using helical CT scan in 14 patients with obstructive disorders involving small and large airways, and 2 with restrictive lung disease. The data set of 7-second, continuous helical scan at constant table position were reconstructed as 35 one-second temporarily overlapping images at 0.2- second intervals over 2-3 respiratory cycles, and regional CT densitometry was displayed. Normal lungs (5 volunteers) showed a regular sinusoidal curve, and maximal lung density change (LDC) was greater independent lungs than in independent lungs, with an average difference of 29.5 HU, indicating the gravitational effect In contrast, a regular sinusoidal curve was not shown in obstructive disorders, and a significant reduction in maximal LDC (33.7 +/- 22.6 HU) compared with the normal lungs (60.8 +/- 25.9 HU) (P < 0.001) was indicated. In contrast, no marked reduction in maximal LDC (53.7 +/- 28.6 HU) was shown in restrictive disorders. This method is fast and easy, and appears useful for the detection of ventilation abnormalities in obstructive lung disorders.

Cytokine-induced neutrophil chemoattractant (CINC)-2 alpha, a novel member of rat GRO/CINCs, is a predominant chemokine produced by lipopolysaccharide-stimulated rat macrophages in culture

Neutrophil chemotactic factors (chemokines) have been purified from conditioned medium of lipopolysaccharide (LPS)-stimulated rat macrophages in culture. The LPS-stimulated macrophages produced one acidic chemokine, rat macrophage inflammatory protein (MIP)-1alpha, and four basic chemokines, cytokine-induced neutrophil chemoattractant (CINC)-1. CINC-2alpha, CINC-2beta and CINC-3/rat MIP-2. CINC-2alpha, a novel chemokine recently isolated from conditioned medium of rat granulation-tissue culture, was the major chemoattractant among these four basic chemokines. The results suggest that CINC-2alpha is produced by activated macrophages in vivo and plays an important role in the infiltration of neutrophils into inflammatory sites in rats

The role of spreading depression in focal ischemia evaluated by diffusion mapping

This study investigated the role of spontaneous and induced spreading depression (SD) on the evolution of focal ischemia in vivo. We induced focal ischemia in 12 rats using the middle cerebral artery suture occlusion (MCAO) method. Chemical stimulation of nonischemic ipsilateral cortex by potassium chloride application (KCl group; n = 7) and saline (NaCl group; n = 5) was performed at 15, 30, 45, and 60 minutes following MCAO, and SD was detected electrophysiologically. Ischemic lesion volumes assessed over 15-minute intervals, evaluated by continuous apparent diffusion coefficient (ADC) of water mapping, demonstrated that the ischemic region increased significantly during 15-minute time epochs with a single SD episode (36.5 +/- 12.9 mm3, mean +/- SD) or multiple SD episodes (39.8 +/- 22.3) compared with those without SD (13.9 +/- 11.5) (p = 0.0009). Infarct volume at postmortem 24 hours after MCAO was significantly larger in the KCl group, with more total SDs (237.8 +/- 13.8) than the NaCl group (190.5 +/- 12.6) (p = 0.0001). This study demonstrates that ischemia-related and induced SDs increase significantly ischemic lesion volume in vivo, supporting the hypothesis for a causative role of SD in extending focal ischemic injury.

[Small cell lung cancer associated with ectopic ACTH syndrome]

A 70-year-old woman was referred to our hospital for diagnosis and treatment of a pulmonary mass detected on a chest X-ray film. Small cell lung cancer was diagnosed from pathological examination of a specimen of the tumor obtained by transbronchial biopsy. Paraneoplastic Cushing's syndrome was diagnosed on the basis of an elevated serum ACTH level (2000 pg/ml), the serum cortisol level (171.9 micrograms/dl), elevated excretion of urinary 17-OHCS (67 mg/day), persistent hypokalemia, metabolic alkalosis, hyperglycemia, central obesity, hypertension, systemic pigmentation, and the lack of a history of diabetes mellitus. Immunohistochemical staining with a polyclonal anti-ACTH antibody of a biopsy specimen from a lymph node with metastasis showed that tumor cells were weakly positive. The patient responded well to intensive chemotherapy with VP-16 (100 mg/m2 day 103), CBDCA (100 mg/m2 day 1-3), and CDDP (80 mg/m2 day 1). Complete response was obtained after 6 courses of chemotherapy. The serum ACTH level decreased rapidly as the tumor shrank. The primary tumor, however, relapsed after 3 months and the patient died of progressive disease, 11 months after diagnosis.

Development in vitro of preimplantation embryos from 55 mouse strains

Mouse pronuclear embryos were obtained by in vitro fertilization with oocytes of 55 strains of immature females by gonadotrophin-induced ovulation and epididymal sperm of Slc:ICR strain. The number of oocytes ovulated with hormones (5.3-49.4 oocytes per head; average, 22.6), rates of in vitro fertilization (12.2-95.3%; average, 70.7%) and subsequent preimplantation development in Whitten's medium (WM) varied greatly among strains. F1 hybrids developed significantly better than other strains of mice and outbred animals did not develop as well as inbred animals. Within inbred mice, coat colour had no significant effect. In addition, the observation of preimplantation development in WM supplemented with ethylenediamine tetraacetic acid (EDTA) showed that the beneficial effect of the chelator was not universal to mouse embryos; EDTA had a good effect on ICR and PW/aSlc embryos but not on AKR or ddY embryos. The results indicate that strain differences should be considered when interpreting reproductive experiments using mouse embryos.

Serum albumin for estimating creatinine clearance in the elderly with muscle atrophy

The present study was conducted to develop a special formula to predict creatinine clearance (CCr, ml/min) in the elderly with chronic muscle atrophy using serum albumin (Alb, g/dl). We obtained 90 data sets including actual body weight (BW, kg), urinary creatinine excretion (UCr, mg/24 h), serum creatinine (SCr, mg/dl), and Alb from 90 inpatients aged 60-92 years. Regression equations were determined between the dependent variable of UCr/BW and the explanatory variable of Alb as follows: For males Ucr/BW = 2.695 Alb + 4.665 For females Ucr/BW = 1.827 Alb + 4.146. Then, the new predictive formula was derived from the equations: For males CCr = (19Alb + 32)BW/(100 x SCr) For females CCr = (13Alb + 29)BW/(100 x SCr). Evaluations for the predictive error (predicted CCr- measured CCr) showed that the new formula could provide more accurate and less biased estimates of CCr than the Cockcroft and Gault formula could, even in patients with renal insufficiency and in those with Alb < or = 2.8 g/dl.

CCAAT/enhancer-binding proteins alpha and beta interact with the silencer element in the promoter of glutathione S-transferase P gene during hepatocarcinogenesis

We have previously identified a silencer in the glutathione S-transferase P (GST-P) gene which is strongly and specifically expressed during chemical hepatocarcinogenesis. At least three trans-acting factors bind to multiple cis-elements in the silencer. One of them, Silencer Factor-B (SF-B), is identical with CCAAT/enhancer-binding protein beta (C/EBP beta) and binds to GST-P Silencer 1 (GPS1). Many C/EBP beta binding sites are recognized by each of the C/EBP isoforms. Western blot analyses of C/EBP isoforms during chemical hepatocarcinogenesis revealed a decrease of C/EBP alpha expression. However, there was no change in C/EBP beta level. In the nuclear extracts from normal liver, C/EBP alpha was the dominant form that bound to GPS1, whereas both C/EBP alpha and C/EBP beta bound to GPS1 in the nuclear extracts from carcinogenic liver. Furthermore, transfection assays showed that C/EBP alpha not only repressed the GST-P promoter activity but also attenuated the transcriptional stimulation by C/EBP beta. These observations strongly suggest that the ratio of C/EBP alpha to C/EBP beta is one of the important factors for the GST-P silencer activity, and the decrease of this ratio during hepatocarcinogenesis reduces the silencer activity and, consequently, increases the GST-P expression.

Contribution of hydrophobic residues to the stability of human lysozyme: calorimetric studies and X-ray structural analysis of the five isoleucine to valine mutants

In order to understand the contribution of hydrophobic residues to the conformational stability of human lysozyme, five Ile mutants (Ile --> Val) in the interior of the protein were constructed. The thermodynamic parameters characterizing the denaturation of these mutant proteins were determined by scanning calorimetry, and the three-dimensional structure of each mutant protein was solved at high resolution by X-ray crystallography. The thermodynamic analyses at 64.9 degrees C and at pH 2.7 revealed the following. (1) The stabilities of all the mutant proteins were decreased as compared with that of the wild-type protein. (2) The changes in the calorimetric enthalpies were larger than those in the Gibbs energies, and were compensated by entropy changes. (3) The destabilization mechanism of the mutant proteins differs, depending on the location of the mutation sites. X-ray analyses showed that the overall structures of all the mutant human lysozymes examined were identical to that of the wild-type protein, and only small structural rearrangements were observed locally around some of the mutation sites. The most striking change among the mutant proteins was found in the mutant protein, 159V, which contains a new water molecule in the cavity created by the mutation. The thermodynamic stabilities of the mutant proteins are discussed in light of the high-resolution X-ray structures of the wild-type and five mutant human lysozymes examined.

Lysozyme in the ovary of tilapia (Oreochromis mossambicus): its purification and some biological properties

Lysozyme was purified from the ovary of tilapia, Oreochromis mossambicus, with two steps, chitin coated-cellulose and Sephadex G-100, and its biological properties were investigated. Purified lysozyme had a molecular mass of 15kDa on SDS-PAGE under reducing condition. Analyses with antibody (a-EL) against the purified lysozyme revealed that serum and egg extract reacted with a-EL and the precipitin lines fused completely. The enzyme activities in serum and egg extract were inhibited by adding serially diluted a-EL. Therefore, egg extract and serum lysozyme was immunologically identical. Immunohistochemically, lysozyme was observed in the ooplasm of the oocytes laden with yolk but not in the follicle layers, egg envelope or immature oocytes (the peri-nucleolus stage). In addition, the enzyme activity in the large oocytes was higher than that in the small ones. These results suggest that lysozyme detected in the oocytes is derived from extra-ovarian tissue and transfers from the maternal circulation. Lysozyme activity in the serum of female tilapia increased with oocyte development, suggesting that the change in the enzyme level may be partially related to the reproductive events (especially vitellogenesis) of the female fish.

The penumbra, therapeutic time window and acute ischaemic stroke

There is a great deal of evidence that an ischaemic penumbra exists in animals and humans after the occurrence of focal brain ischaemia (Hossmann, 1994). The concept of the penumbra leads to the idea of a therapeutic time window. Because, if the region of irreversible injury (infarction) after focal ischaemia evolves in time and space, then the possibility of therapy to interfere becomes a tenable hypothesis. All of the acute stroke therapies given after onset have their basis from this hypothesis of a therapeutic time window (Fisher, 1995). As previously alluded to, a more apt term might be a window-shade, because this metaphor suggests a more dynamic event. The time and location of potentially salvageable ischaemic brain tissue after ischaemic stroke is a moving target and many unanswered questions remain. The data from animal stroke models support 2-3 hours as the time when intervention is likely to be beneficial in rats. Non-human primate data are scarce, but the few studies available do imply that at 3-4 hours after stroke onset some ischaemic tissue remains potentially salvageable. In humans, we really do not know what the time window is and we must remember that it is likely to be highly variable among individuals. This variability relates to many factors including the status of collateral flow, patient age, coexistent metabolic abnormalities (i.e. hyperglycaemia), premorbid medications and many other confounding variables. All acute stroke intervention trials are trying to initiate therapy within 6-8 hours after onset and the earlier, presumably the better. However, this approach is based upon population averaging, since we have had no convenient and reliable mechanism to determine, if an individual patient has viable tissue when therapy can be started. The availability of an imaging modality that could distinguish the presence and extent of salvageable ischaemic tissue would greatly facilitate stroke therapy trials and ultimately the selection of patients when proven therapies are available. The new MRI techniques might afford this possibility. As we enter the exciting era of effective therapy for acute ischaemic stroke, the issues surrounding the therapeutic time window(shade) will become more critical, because it is this critical time that will define the success or failure of our interventions. Therefore it is incumbent upon basic stroke researchers and clinicians to continue to define the ischaemic penumbra and to develop readily applicable mechanisms to identify and treat this moving target.

Occupational exposure in pediatric cardiac catheterization

Radiation doses to staff involved with pediatric cardiac catheterization were measured using thermoluminescent dosimeters in 18 procedures. The average doses to the lens and thyroid, and the effective dose per procedure to the main operating physicians was 88, 180, and 8 microSv, respectively; to assistant physicians, 23, 51, and 2 microSv; and to technicians, 23, 27, and 2 microSv. In some procedures, the dose to the technician's hand approached 1,500 microSv. The doses received by physicians were proportional to cineangiographic time but with no correlation with integrated currents. The number of procedures which may be performed in a year by individual staff members was estimated to be 430 and 2,780 procedures for physicians and assistants, respectively. It was suggested that the front of the neck is an adequate position for the dosimeter to measure doses during pediatric catheterization.

Zonisamide: electrophysiological and metabolic changes in kainic acid-induced limbic seizures in rats

We studied the pharmacological mechanism of zonisamide (ZNS) using an electrophysiological and autoradiographical method in a limbic seizure model in rats. Limbic seizure status epilepticus was induced by a unilateral microinjection of kainic acid (KA) into the amygdala. Initially, observed seizures were limited to the side of the injected amygdala and then propagated to bilateral sensorimotor cortex. Eighty minutes after injection, secondarily generalized seizure status epilepticus was induced, with each seizure lasting approximately 30 s and recurring every 5 min. ZNS 100 mg/kg was administered intravenously (i.v.) during the generalized seizure. Forty minutes after ZNS administration, epileptic activity was observed only at the KA-injected amygdalar site and spikes were not observed in the bilateral sensorimotor cortex. We studied local cerebral glucose utilization (LCGU) after ZNS or saline administration using an autoradiographical method in the same limbic seizure preparation. In the ZNS group, LCGU decreased in the ipsilateral sensorimotor cortex and hippocampus, whereas in the controls LCGU increased in these structures. On the other hand, ZNS did not suppress the epileptic activity of the primary focus and no decrease in LCGU was observed in the KA-injected amygdala. ZNS inhibited seizure propagation from the epileptogenic focus but did not suppress the epileptic activity of the focus. Our results suggest that ZNS is effective for the treatment of secondarily generalized seizure.

Increase of plasma sialic acid upon UV-B irradiation in mouse

In many inflammatory conditions including burns, the plasma sialic acid level rises as an acute responder. Sunburn is a kind of burn. In this study, sunburn was experimentally caused in mice by UV-B irradiation and their plasma sialic acid levels were measured. The levels increased, and reached the maximum 3 d after irradiation. This level was maintained for about 2 d, then it returned to normal within about one week. The increase in the level correlated with the UV dose and the severity of inflammation resulting in sunburn. This assay system was applied to assess the virtue of UV-cut cream in experimental sunburn.

Protein kinase C-mediated inhibition of an inward rectifier potassium channel by substance P in nucleus basalis neurons

In nucleus basalis neurons, substance P (SP) causes a slow excitation, mediated through a pertussis toxin-insensitive G protein, by suppressing an inward rectifier K+ channel. Here we report that SP applied outside the patch pipette inhibited the single-channel activity, recorded on-cell, of the inward rectifier. The PKC inhibitors staurosporine and PKC(19-36) suppressed this effect in whole-cell mode and in on-cell single-channel mode. A diacylglycerol analog mimicked the SP effect, and PKC(19-36) suppressed this analog effect. SP irreversibly suppressed the inward rectifier in neurons treated with okadaic acid. These results indicate that a diffusible messenger mediates the SP effect, that its signal transduction involves phosphorylation by PKC, and that dephosphorylation by a serine/threonine protein phosphatase mediates its recovery.

Frequent natural killer cell abnormality in children in an area highly contaminated by the Chernobyl accident

Since January 1991, we have been performing thyroid surveys and hematologic and immunologic screening on children in Chechersk, Belarus, a city situated in one of the areas most seriously contaminated with high levels of radionuclides after the Chernobyl accident. Ten children selected from 713 children because of goiter did not show a decrease in humoral immunity or in the number and function of T cells. By contrast, natural killer (NK) cell activity against K562 cells was depressed in 4 of these 10 children. The clinical and laboratory findings indicated that previously reported diseases with NK cell dysfunction could be excluded. A comparative analysis of NK cell activity in children from areas with and without high 137Cs levels revealed a high frequency of abnormal NK cell activity only in children from the area contaminated by radioactive fallout. In addition, there was no correlation between NK cell activity and NK cell number as percentage in the children from the area with high 137Cs levels. Neither activity nor number of NK cells was correlated with the body content of 137Cs. Thus, the frequent abnormality of NK cell function may not have been due to actual internal exposure to the long-lived radionuclide.

Mechanisms of action of somatostatin on human TSH-secreting adenoma cells

The mechanisms of somatostatin (SRIH) action on thyroid-stimulating hormone (TSH) secretion were examined using human TSH-secreting adenoma cells. SRIH (10(-7) M) inhibited TSH secretion through a pertussis toxin-sensitive G protein. SRIH also inhibited forskolin- and 8-bromo-adenosine 3',5'-cyclic monophosphate (8-BrcAMP)-induced TSH secretion. The mechanisms of this inhibition were investigated by measuring intracellular Ca2+ concentration ([Ca2+]i) and by electrophysiological experiments. Application of 10(-7) M SRIH reduced the [Ca2+]i, whereas forskolin and 8-BrcAMP increased the [Ca2+]i. Simultaneous application of SRIH abolished the forskolin-and the 8-BrcAMP-induced [Ca2+]i increase, indicating that the SRIH-induced decrease in [Ca2+]i was independent of the reduction in intracellular cAMP. Under current clamp using the whole cell clamp, 10(-7) M SRIH hyperpolarized the membrane and arrested Ca(2+)-dependent action potentials, which accounted for the SRIH-induced decrease in [Ca2+]i. Voltage clamp experiments revealed that this membrane hyperpolarization resulted from the activation of an inward-rectifying K+ current through a pertussis toxin-sensitive G protein. Intracellular injection of cAMP (100 microM) through the patch pipette did not abolish the SRIH-induced K+ current, indicating that the activation of SRIH-induced K+ channels was independent of intracellular cAMP. From these data, we concluded that SRIH-induced membrane hyperpolarization was responsible for the [Ca2+]i decrease, which in turn inhibited TSH secretion. Application of thyrotropin-releasing hormone (TRH; 10(-7) M) caused an increase in the [Ca2+]i, composed of an initial transient increase followed by a sustained increase. SRIH inhibited the sustained increase in [Ca2+]i. SRIH also inhibited the TRH-induced decrease in the membrane conductance.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional ventilatory evaluation using dynamic SPET imaging of xenon-133 washout in obstructive lung disease: an initial study

Regional ventilatory abnormalities in obstructive lung disease were evaluated by dynamic single-photon emission tomography (SPET) of pulmonary washout of xenon-133 (133Xe) gas. The subjects included seven healthy volunteers. 17 patients with obstructive lung disease, and seven patients with restrictive lung disease. Following 6 min of inhalation of 133Xe gas (60-72 MBq/l), equilibrium and subsequent washout SPET images during spontaneous breathing were sequentially acquired every 30 s for 6-7 min, using a triple-head SPET system with the return mode of continuous repetitive rotating acquisition. A gravity-induced gradient of ventilation was demonstrated in the volunteers' lungs. Compared with the normal subjects, all the patients with obstructive disease showed abnormal 133Xe retention on the washout SPET images, with or without abnormalities on chest X-ray computed tomography, whereas the patients with restrictive disease did not show any significant delays in washout. This modality may assist in the evaluation of the three-dimensional dynamic process of ventilatory abnormalities in obstructive lung disease.