Mcl-1, a member of the Bcl-2 family, delays apoptosis induced by c-Myc overexpression in Chinese hamster ovary cells

Mcl-1, a protein increased early in the differentiation of human myeloblastic ML-1 cells, has sequence similarity to Bcl-2. In the present study, we determined whether Mcl-1 has functional similarity to Bcl-2 by testing its ability to inhibit apoptosis induced by c-Myc overexpression. This was carried out using Chinese hamster ovary 5AHSmyc cells which contain the human c-myc proto-oncogene under the control of a heat shock promoter. Heat treatment induces c-Myc overexpression and thus apoptosis as determined by internucleosomal DNA fragmentation. We transfected 5AHSmyc cells with mcl-1 and found that clones expressing the introduced Mcl-1 protein exhibited reduced DNA fragmentation. Mcl-1 was also capable of delaying the onset of cell death as judged by loss of membrane integrity, although it could not provide complete protection from c-Myc overexpression. Thus, Mcl-1 has functional homology to Bcl-2 in that Mcl-1 can enhance cell viability under conditions that otherwise cause apoptosis.

Sequential activation of Raf-1 kinase, mitogen-activated protein (MAP) kinase kinase, MAP kinase, and S6 kinase by hyperosmolality in renal cells

In the renal medulla during antidiuresis, the extracellular fluid becomes hyperosmotic. Madin-Darby canine kidney (MDCK) epithelial cells adapt in hyperosmotic conditions and serve as a useful tissue culture model for cellular responses to hyperosmolality. We demonstrate that hyperosmolality stimulates phospholipase C, Raf-1 kinase mitogen-activated protein (MAP) kinase kinase, MAP kinase, and S6 kinase activities and that it increases phosphorylation of Raf-1 kinase, and p42 MAP kinase in MDCK cells. Stimulation of these kinases is osmolality-dependent (from 300 to 600 mosm/kg H2O). The time course of activation is sequential; the peak stimulation for Raf-1 kinase is at 5 min, at 10 min for MAP kinase kinase and MAP kinase, and at 20 min for S6 kinase. The activation of Raf-1 kinase and MAP kinase is inhibited by phorbol 12-myristate 13-acetate pretreatment in the presence of calphostin C or H-7. Tyrosine kinase inhibitors (genistein, herbimycin) do not significantly suppress hyperosmolality-induced MAP kinase activity. The increase of Ins-1,4,5-P3 levels by hyperosmolality suggests that activation of these kinases is mediated at least partially via activation of phospholipase C. Thus, hyperosmolality stimulates the serine/threonine kinases, Raf-1 kinase, MAP kinase kinase, MAP kinase, and S6 kinase, via predominantly protein kinase C-dependent, tyrosine kinase-independent pathways in MDCK cells.

[Reconfirmation of golgiphobic dendrites of the motoneurons in rat spinal cord]

With CB-HRP method (injections into 5 muscles of anterior and posterior extremities) and Golgi technique, the corresponding sections of spinal cords were observed on same aged rats of the identical parent rats. Comparing the cell numbers of the lateral groups of anterior horns, the former (CB-HRP) revealed twice as many as the cell numbers of the latter (Golgi). As to the surface densities of the white matter dendrites (WMD) in the lateral funiculi from the neurons of the lateral groups of the anterior horns, the density revealed by injection of CB-HRP to the tibialis anterior is 2-9 times more than that in Golgi sections. All of WMD revealed in CB-HRP sections could extend into the peripheral portions of the lateral funiculi, and quite a few of them even form a subpial marginal plexus, that is one example of Golgiphobic dendrites (GBD). For labeled medial cell groups of the anterior horn with CB-HRP, their dendrites could reach to the ependymal layer of the central canal (another GBD). These two types of GBD were not present on the Golgi material. The significance of GBD was also discussed.

K+ currents and K+ channel mRNA in cultured atrial cardiac myocytes (AT-1 cells)

Atrial tumor myocytes derived from transgenic mice (AT-1 cells) maintain a well-differentiated cardiac biochemical and histological phenotype. In addition, they beat spontaneously in culture and exhibit long action potentials whose repolarization resembles that observed in native mammalian myocytes. In this study, we identified the major depolarization-activated outward currents in AT-1 cells; also, the presence of mRNAs that encode outwardly conducting ion channels was determined by cloning from an AT-1 cDNA library or by Northern hybridization. Among K+ channel isoforms, Kv2.1, minK, and Kv1.4 were readily detected in tumors and at 1 day in culture. Their abundance remained relatively stable (twofold or less change) after 14 days. The major outward current in AT-1 cells is a delayed rectifier that displays prominent inward rectification, activates rapidly (eg, 182 +/- 27 milliseconds [mean +/- SEM] at + 20 mV, n = 12), exhibits biexponential deactivation kinetics, and is extremely sensitive to the methanesulfonanilide dofetilide (IC50, 12 nmol/L). These characteristics identify this current as IKr, a delayed rectifier observed only in cardiac cells. IKr in AT-1 cells displayed slow inactivation: dofetilide-sensitive deactivating tails were greater after 1-second than after 5-second pulses. When IKr was blocked by > or = 0.5 mumol/L dofetilide, time-independent current was usually recorded (50 of 65 experiments); rapidly inactivating (6 of 65) or slowly inactivating (9 of 65) outward currents were occasionally observed. We conclude that AT-1 cells express mRNAs encoding cardiac K+ channels and display a cardiac electrophysiological phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)

PCR localization of C-type natriuretic peptide and B-type receptor mRNAs in rat nephron segments

The present study was undertaken to investigate the presence of C-type natriuretic peptide (CNP) mRNA and its receptor, natriuretic peptide B-type receptor (ANPR-B) mRNA, in rat renal structures. The microlocalization of mRNAs coding for CNP and ANPR-B was carried out in the rat kidney, using an assay of reverse transcription and polymerase chain reaction (RT-PCR) in individual microdissected renal tubule segments, glomeruli, vasa recta bundle, and arcuate arteries. The PCR signal for CNP was detected in glomerulus, vasa recta bundle, and arcuate artery. The PCR product of ANPR-B was widely present in renal structures. Relatively large amounts of ANPR-B PCR product were detected in glomerulus, vasa recta bundle, arcuate artery, and distal nephron segments. A relatively high concentration of CNP (10(-7) M) stimulated guanosine 3',5'-cyclic monophosphate accumulation in glomerulus, medullary thick ascending limb, cortical collecting duct, and inner medullary collecting duct. Our data demonstrate that CNP can be produced locally in the glomerulus and renal vascular system and that ANPR-B is widely distributed in renal structures. Thus CNP may influence renal function and act in autocrine and paracrine fashions in the kidney.

Distribution of kallikrein-binding protein mRNA in kidneys and difference between SHR and WKY rats

We investigated kallikrein-binding protein (KBP) mRNA distribution in the kidney of Sprague-Dawley (SD) rats, spontaneously hypertensive rats (SHR), and Wistar-Kyoto strain (WKY) rats. Northern blot analysis revealed that KBP mRNA was located mainly in the medulla and with lower amounts in SHR than in WKY rats. KBP mRNA in microdissected nephron segments was detected by reverse transcription and polymerase chain reaction (RT-PCR) followed by Southern blot analysis. In SD rats, the most abundant signals were consistently found in inner medullary collecting duct (IMCD), with small amounts in outer medullary collecting duct, proximal convoluted tubule, and glomerulus. No signals were found in connecting tubule and cortical collecting duct. The nephron distribution of KBP mRNA was similar in WKY and SD rats. Only a small amount of signal was found, however, in IMCD of SHR. In conclusion, 1) KBP mRNA was predominantly distributed in the medullary segments of the distal nephron, downstream from the known kallikrein activity site in the collecting duct, and 2) KBP mRNA expression was significantly decreased in the kidney of SHR.

[Study of bronchoalveolar lavage fluid harvested from the dogs with steam inhalation injury]

The significances of analyzing bronchoalveolar lavage fluid (BALF) were studied using a steam inhalation injury model. Bronchoalveolar lavage was carried out at 1 and 5 h after steam inhalation injury. The parameters investigated included cellular analysis, the total protein content, malondialdehyde (MDA) content, the activity of superoxide dismutase (SOD), and the angiotensin converting enzyme (ACE) in the BALF, and pathologic examination of lungs. The study indicated that some informations of the pathophysiological changes in the lungs after inhalation injury could be acquired by the BALF analysis.

Localization of cyclophilin A and cyclophilin C mRNA in murine kidney using RT-PCR

Cyclosporin A (CsA), which is widely used as an immunosuppressant, has a nephrotoxic side effect. The mechanism of this nephrotoxicity is not well understood; however, recent studies suggest that cyclophilin (cyp) is responsible for mediating the immunosuppressive action of CsA through the interaction with the Ca(2+)- and calmodulin-dependent phosphatase, calcineurin. While cyp A mRNA is expressed ubiquitously, cyp C mRNA has been shown to be topically expressed, including in the kidney. We examined: (1) distribution of cyp A and cyp C mRNA in microdissected murine nephron segments, using a combination of reverse transcription and polymerase chain reaction (RT-PCR) techniques, and (2) the effect of CsA administration on cyp C mRNA expression in proximal convoluted tubule. Among the nephron segments examined, large signals for cyp C PCR product were detected in proximal convoluted tubule and proximal straight tubule. Our data showed that the distribution of cyp C mRNA was uneven, and it mainly existed in segments that are relatively sensitive to CsA toxicity. In contrast, cyp A mRNA was found to be distributed almost equally along the nephron segments examined. By CsA administration, the signal for cyp C mRNA PCR product was increased. These results suggest that cyp C may play some role in the renal tubular disorder observed in CsA nephrotoxicity.

Antecedent sympathetic stimulation alters time course of chronotropic response to vagal stimulation in dogs

We determined the influence of antecedent sympathetic stimulation on the chronotropic responses of the heart to 10-s strains of vagal stimulation in anesthetized dogs. We used the reciprocal of the slope (m-1) of the initial portion of the vagal response as an index of the time required for the response to reach steady state. In one group of 11 animals, we found that the onset of the response to the vagal stimulation was progressively blunted as we increased the frequency and duration of the antecedent sympathetic stimulation; that is, m-1 increased from 0 to 8.13 +/- 2.75 (SE) and from 0 to 8.22 +/- 2.26, respectively. In three other animals, an antecedent infusion of norepinephrine had a blunting effect that resembled that of antecedent sympathetic stimulation. In 11 other animals, m-1 significantly decreased as we prolonged the elapsed time from the end of sympathetic stimulation to the beginning of vagal stimulation. In six other animals, m-1 was not affected by antecedent atrial pacing at frequencies that were equivalent to those elicited by antecedent sympathetic stimulations. The blunting effect of antecedent sympathetic stimulation was abolished by propranolol administration (1 mg/kg), but it was not affected appreciably by phentolamine administration (2 mg/kg). We conclude that the major blunting effect of antecedent sympathetic stimulation is mediated postjunctionally (i.e., at the level of the automatic cells in the heart.

Enzymatic protection from autoxidation for crosslinked hemoglobins

The autoxidation rates of hemoglobins crosslinked between the alpha subunits (alpha 99XLHb A) and between the beta subunits (beta 82XLHb A) were reduced in the presence of catalase and/or superoxide dismutase. In the presence of catalase the rate for alpha 99XLHb A decreased 2.3 fold and for beta 82XLHb A, 1.9 fold. Superoxide dismutase reduced the rate 1.6 fold for alpha 99XLHb A and 1.8 fold for beta 82XLHb A. In the presence of both catalase and superoxide dismutase the rate of autoxidation decreased by 3.0 fold in alpha 99XLHb A and 4.0 fold in beta 82XLHb A. The presence of catalase and superoxide dismutase or both in the crosslinked hemoglobin samples increases the autoxidation half-life of oxyhemoglobins. This suggests that crosslinked hemoglobins to be used as blood substitutes could be protected from oxidation in storage by these enzymes.

Expression of endothelin-3 mRNA along rat nephron segments using polymerase chain reaction

Endothelin (ET) is now known to be a family of three distinct peptides. Although many reports have studied the renal action of ET-1, comparatively little is known concerning ET-3. We previously reported that ET-1 mRNA is expressed in glomerulus (Glm) and inner medullary collecting duct (IMCD). In this study, microlocalization of mRNA coding ET-3 was carried out in the rat kidney using a reverse transcription and polymerase chain reaction (RT-PCR) assay of individual microdissected renal tubule segments along the nephron, Glm, vasa recta bundle, and arcuate arteries. Large signals for ET-3 PCR product were detected in proximal convoluted and straight tubules, cortical collecting duct, and outer medullary collecting duct. Glm, IMCD, and vasa recta bundle also expressed relatively large amounts of ET-3 mRNA. Small signals were found in medullary thick ascending limb, inner medullary thin limb, and arcuate artery. We detected ET-3 protein in tubule suspensions from cortex, outer medulla, and inner medulla of rat kidney. Furthermore, incubation with TGF-beta did not change ET-3 PCR signal, whereas ET-1 PCR signal was increased significantly by exposure to TGF-beta in Glm and IMCD. Thus, ET-3 and ET-1 are distributed differently along the nephron and are regulated in different manners. This suggests that ET-3 and ET-1 may affect kidney functions in different ways.

Different localization and regulation of two types of vasopressin receptor messenger RNA in microdissected rat nephron segments using reverse transcription polymerase chain reaction

Recent studies have revealed that arginine vasopressin (AVP) has at least two types of receptors in the kidney: V1a receptor and V2 receptor. In this study, microlocalization of mRNA coding for V1a and V2 receptors was carried out in the rat kidney using a reverse transcription and polymerase chain reaction. Large signals for V1a receptor PCR product were detected in the glomerulus, initial cortical collecting duct, cortical collecting duct, outer medullary collecting duct, inner medullary collecting duct, and arcuate artery. Small but detectable signals were found in proximal convoluted and straight tubules, inner medullary thin limbs, and medullary thick ascending limbs. Large signals for V2 receptor mRNA were detected in the cortical collecting duct, outer medullary collecting duct, and inner medullary collecting duct. Small signals for V2 receptor were found in the inner medullary thick limbs, medullary thick ascending limbs, and initial cortical collecting duct. Next, we investigated V1a and V2 receptor mRNA regulation in the dehydrated state. During a 72-h water restriction state, the plasma AVP level increased and V2 receptor mRNA decreased in collecting ducts. In contrast, V1a receptor mRNA did not change significantly. Thus, the two AVP receptor subtypes are distributed differently along the nephron, and these mRNAs are regulated differently in the dehydrated state.

Calcium ATPase of sarcoplasmic reticulum has four binding sites for calcium

The calcium-transporting ATPase of sarcoplasmic reticulum is known to bind two Ca2+ ions from the cytoplasm to the free enzyme and two Ca2+ ions from the lumen to the phosphoenzyme. The concentration of phosphoenzyme formed at equilibrium from Pi and Mg2+ increases with increasing concentration of calcium in the lumen, which binds to the phosphoenzyme to form Ca2.E approximately P.Mg. However, at subsaturating concentrations of Mg2+ increasing the concentration of lumenal Ca2+ does not drive phosphoenzyme formation to completion. The maximal levels of phosphoenzyme that are formed at saturating concentrations of lumenal Ca2+ increase with increasing concentrations of Mg2+. This result requires that Ca2+ can bind to low-affinity lumenal sites on both the free enzyme and the phosphoenzyme, as well as to the high-affinity cytoplasmic calcium-binding sites. If there were no lumenal binding sites for Ca2+ on the free enzyme, high concentrations of lumenal Ca2+ would convert all of the enzyme to the same maximal concentration of Ca2.E approximately P.Mg at subsaturating concentrations of Mg2+ and Pi. We conclude that there are two low-affinity lumenal sites as well as two high-affinity cytoplasmic sites for Ca2+ on the free enzyme. Phosphorylation by ATP results in translocation of Ca2+ from the high-affinity to the low-affinity sites.

Magnitude and Kinetics of Stem Elongation Induced by Exogenous Indole-3-Acetic Acid in Intact Light-Grown Pea Seedlings

Exogenously applied indole-3-acetic acid (IAA) strongly promoted stem elongation over the long term in intact light-grown seedlings of both dwarf (cv Progress No. 9) and tall (cv Alaska) peas (Pisum sativum L.), with the relative promotion being far greater in dwarf plants. In dwarf seedlings, solutions of IAA (between 10-4 and 10-3 M), when continuously applied to the uppermost two internodes via a cotton wick, increased whole-stem growth by at least 6-fold over the first 24 h. The magnitude of growth promotion correlated with the applied IAA concentration from 10-6 to 10-3 M, particularly over the first 6 h of application. IAA applied only to the apical bud or the uppermost internode of the seedling stimulated a biphasic growth response in the uppermost internode and the immediately lower internode, with the response in the latter being greatly delayed. This demonstrates that exogenous IAA effectively promotes growth as it is transported through intact stems. IAA withdrawal and reapplication at various times enabled the separation of the initial growth response (IGR) and prolonged growth response (PGR) induced by auxin. The IGR was inducible by at least 1 order of magnitude lower IAA concentrations than the PGR, suggesting that the process underlying the IGR is more sensitive to auxin induction. In contrast to the magnitude of the IAA effect in dwarf seedlings, applied IAA only doubled the growth in tall seedlings. These results suggest that endogenous IAA is more growth limiting in dwarf plants than in tall plants, and that auxin promotes stem elongation in the intact plant probably by the same mechanism of action as in isolated stem segments. However, since dwarf plants to which IAA was applied failed to reach the growth rate of tall plants, auxin cannot be the only limiting factor for stem growth in peas.

Constitutive activation of opsin: influence of charge at position 134 and size at position 296

In previous studies, mutation of Lys296 or Glu113 in opsin has been shown to result in constitutive activation of the protein--that is, these mutants can activate the G protein transducin in the absence of chromophore and in the absence of light. These and other data have led to the suggestion that a salt bridge between Lys296 and Glu113 helps to constrain opsin to an inactive conformation. It is shown here that of 12 different amino acids substituted at position 296, all, except Arg and the wild-type Lys, are constitutively active at neutral pH, lending further support to this suggestion. However, activation of opsin appears also to be influenced significantly by the size of amino acid side chain at position 296. Thus, there are multiple effects of the mutations. Wild-type opsin is also shown to be weakly active at pH 6.1. Five other charged amino acids in the membrane-embedded region of the protein (Asp83, Glu122, Glu134, Arg135, and Glu201) were mutated to see if they affect constitutive activity. Of these amino acids, only mutation of Glu134 results in an increase in the activity of opsin. Changing Glu134 to Gln increases the activity of opsin, while changing Glu134 to Asp inhibits activity. These results suggest that a negative charge on Glu134 is important in stabilizing the inactive state of opsin. Glu134 is highly conserved in all visual pigments and most of the other G protein-linked receptors.

[Helicobacter pylori associated gastritis: a primary study of ammonia and urea in gastric juice and mucus in gastric mucosa]

The mucosa of 46 patients with histological chronic gastritis were cultured for helicobacter pylori (HP) and the ammonia and urea in their gastric juice were also determined. The results showed the average ammonia concentration (1.22 +/- 0.23 mmol/L) in HP positive patients was higher than that of HP negative patients (0.72 +/- 0.25 mmol/L), (P < 0.05). But the average urea concentration (0.45 +/- 0.29 mmol/L) in HP positive patients was lower than that of HP negative patients (2.71 +/- 1.20 mmol/L), (P < 0.05). The higher the level of ammonia stands, the more severe the gastritis is. (rs = 0.556). On the other hand, the quantity of mucus was elevated in 18 patients among 28 patients with HP eradicated by drug treatment, which was significantly different from the patients with HP not eradicated. It is suggested that the epithelium of gastric mucosa and the mucus are the chief components of the gastric mucosa barrier; the presence of HP increases ammonia, and thus damages the gastric epithelium and reduces the quantity of mucus. Consequently, the protective gastric mucosa barrier is damaged, and then comes the liability to HP-associated gastritis.

MCL1, a gene expressed in programmed myeloid cell differentiation, has sequence similarity to BCL2

During their lifespan, immature cells normally pass through sequential transitions to a differentiated state and eventually undergo cell death. This progression is aberrant in cancer, although the transition to differentiation can be reestablished in inducible leukemia cell lines. This report describes a gene, MCL1, that we isolated from the ML-1 human myeloid leukemia cell line during phorbol ester-induced differentiation along the monocyte/macrophage pathway. Our results demonstrate that expression of MCL1 increases early in the induction, or "programming," of differentiation in ML-1 (at 1-3 hr), before the appearance of differentiation markers and mature morphology (at 1-3 days). They further show that MCL1 has sequence similarity to BCL2, a gene involved in normal lymphoid development and in lymphomas with the t(14;18) chromosome translocation. MCL1 and BCL2 do not fall into previously known gene families. BCL2 differs from many oncogenes in that it inhibits programmed cell death, promoting viability rather than proliferation; this parallels the association of MCL1 with the programming of differentiation and concomitant maintenance of viability but not proliferation. Thus, in contrast to proliferation-associated genes, expression of MCL1 and BCL2 relates to the programming of differentiation and cell viability/death. The discovery of MCL1 broadens our perspective on an emerging MCL1/BCL2 gene family and will allow further comparison with oncogene families.

Effect of hyperosmolality on production and mRNA expression of ET-1 in inner medullary collecting duct

The effects of hyperosmolality on the production and mRNA expression of endothelin-1 (ET-1) in inner medullary collecting duct (IMCD) were examined in the present study. Osmolality in incubation media was changed from 290 to 490 or 690 mosmol/kgH2O by adding NaCl, urea, mannitol, or raffinose. A preliminary experiment was carried out using tubule suspension from the inner medulla. Hyperosmolality by NaCl stimulated ET-1 accumulation in rats (from 323.5 +/- 76.3 to 478.0 +/- 108.4 and 573.7 +/- 47.8 pg.mg protein-1 x 24 h-1 in 290, 490, and 690 mosmol/kgH2O, respectively) and rabbits. In contrast, hyperosmolality by urea markedly decreased ET-1 accumulation and hyperosmolality by mannitol showed no effect on it. We next examined whether hyperosmolality changes ET-1 mRNA. After incubation in isotonic or hypertonic solution for 6 h, ET-1 mRNA was determined using reverse transcription and polymerase chain reaction (PCR) in microdissected IMCD and glomerulus. Hyperosmolality by NaCl and raffinose significantly increased the PCR products of ET-1 mRNA in IMCD, whereas mannitol did not. The stimulatory effect of hyperosmolality by NaCl on ET-1 mRNA expression was not observed in glomerulus. Our data suggested a stimulatory effect of hyperosmolality on production and mRNA expression of ET-1 in IMCD but not in glomerulus.

Intense sympathetic stimulation releases neuropeptide Y but fails to evoke sustained coronary vasoconstriction in dogs

We determined whether a 3-minute period of intense cardiac sympathetic stimulation, which is known to release neuropeptide Y (NPY), elicits a sustained poststimulatory coronary vasoconstriction in anesthetized dogs that had received propranolol. We also periodically measured the cardiac chronotropic responses to test vagal stimulations; these responses served as an index of the neuronal release of NPY. In a group of 11 animals, the coronary vascular resistance increased by 14 +/- 4% during the sympathetic stimulation. After cessation of stimulation, however, coronary vascular resistance returned rapidly to its control value. The cardiac responses to the test vagal stimuli were attenuated by approximately 40% after cessation of sympathetic stimulation, and this inhibitory effect persisted for approximately 60 minutes. In a second group of eight dogs, we determined whether the intense sympathetic stimulation potentiates the coronary vascular responses to exogenous norepinephrine (NE). Before sympathetic stimulation, standard intracoronary infusions of NE increased coronary vascular resistance by 14 +/- 2%. Intense antecedent sympathetic stimulation did not alter the coronary vascular responses to subsequent NE infusions. However, the chronotropic responses to test vagal stimuli were initially attenuated by approximately 30%, and this inhibitory effect persisted for approximately 1 hour. In a third group of four dogs, we found that exogenous NPY significantly potentiated the coronary vasoconstriction evoked by NE infusions. The coronary vascular responses to combined infusions of NE and NPY were consistently greater (by approximately 13%) than the sum of the responses to these substances when they were infused separately. We conclude that, even though sufficient NPY appears to be released from the sympathetic nerve endings to inhibit vagal neurotransmission, the quantity of NPY released into the coronary blood vessels under the conditions of our experiments appears to be insufficient either to elicit a sustained coronary vasoconstriction or to potentiate the vasoconstrictor effects of intracoronary NE infusions.

Assessment of beat-by-beat control of heart rate by the autonomic nervous system: molecular biology technique are necessary, but not sufficient

Vagus nerve activity can change heart rate substantially within one cardiac cycle, and the chronotropic effects decay almost completely within one cardiac cycle after cessation of vagal activity. The ability of the vagus nerves to regulate heart rate beat by beat can be explained in large part by the speed at which the neural signal is transduced to a cardiac response and by the rapidity of the processes that restore the basal heart rate when vagal activity ceases. Currently, the question of whether the cardiac cells can transduce the sympathetic neural signals rapidly enough to implement beatwise regulation is controversial. Emphasis on the speed of the processes that initiate the responses may, however, be misplaced. Instead, the processes that terminate the responses to autonomic neural activity (especially those processes that remove the released neurotransmitters) are probably the main determinants of the ability of the vagal and sympathetic systems to affect beatwise control. The norepinephrine (NE) released from the sympathetic nerve endings is removed from the cardiac tissues much more slowly than is the acetylcholine that is released from the vagal terminals. As a consequence of the potential deleterious effects associated with the slow removal of NE, the cardiac neural control system has evolved such that the sympathetic nerves ordinarily release NE at a slow rate. Hence, changes in sympathetic neural activity can alter cardiac behavior only slightly from beat to beat. Hence, beatwise control of cardiac function would be negligible, regardless of how swiftly the sympathetic nerve impulse is transduced to a change in cardiac performance.

Alterations in a voltage-gated K+ current during the differentiation of ML-1 human myeloblastic leukemia cells

A voltage-gated K+ current has been identified in ML-1 human myeloid leukemia cells, with the use of the whole-cell patch-clamp technique. ML-1 cells proliferate in tissue culture as immature myeloblasts and can be induced to differentiate to nonproliferative monocyte/macrophages. In the myeloblastic cells, activation of the K+ current occurs upon depolarization of the membrane potential to above -40 mV; inactivation of this current is also voltage dependent and follows a simple exponential time course with a time constant (Ti) of 900 msec at 0 mV. The current is inhibited by 4-aminopyridine (IC50 of 80 microM at 0 mV), but is much less sensitive to tetraethylammonium of Ba2+. In cells exposed to the differentiation-inducer 12-O-tetradecanoylphorbol-13-acetate (TPA), dramatic alterations in the K+ current occur: upon exposure to 10 nM TPA during whole-cell recording, the amplitude of the voltage-activated current initially increases (within 4 min) and later decreases (at approximately 30-50 min). Upon addition of 0.5 nM TPA to cells in tissue culture, the current shows suppressed activation and accelerated inactivation in the early stages of differentiation (10-fold decrease in Ti at approximately 7 hr) and is completely suppressed in the later stages (3 days). Thus, this voltage-gated K+ current is suppressed early in the induction of differentiation and associated loss of proliferation in myeloid ML-1 cells exposed to TPA; this parallels the fact that channels of a similar type are activated upon the stimulation of proliferation in lymphoid cells exposed to mitogens.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta-actin mRNA-binding proteins associated with the cytoskeletal framework

Association of mRNA with the cytoskeletal framework (CSK) is thought to play a strategic role in the placement of mRNA in the cytoplasm. However, the molecular determinants underlying mRNA/CSK association are completely unknown. To begin addressing this issue, we have employed a binding assay to identify proteins of the CSK compartment of NIH 3T3 cells that bind in-vitro-transcribed 32P-labelled beta-actin mRNA with high affinity. Three proteins, of approximate molecular masses 27, 50 and 97 kDa, were observed to exhibit strong binding. Binding to these proteins took place at physiological salt concentration and withstood washing in 0.5 M salt. Furthermore, binding was unaffected by heparin but was inhibited by unlabelled beta-actin mRNA. Treatment of isolated CSKs with the microfilament-severing agent DNase I abolished all beta-actin mRNA-binding activities, thus suggesting a possible association of beta-actin mRNA with the microfilament network in situ. Removal of the 3' untranslated region (UTR) significantly reduced beta-actin mRNA binding to all three CSK proteins but removal of the 5' UTR mainly affected binding to the 97-kDa species and that to a lesser extent. beta-Tubulin mRNA bound to the same three CSK proteins as did beta-actin mRNA, but with considerably less avidity. In contrast, vimentin mRNA strongly recognized these CSK proteins, and further bound to a group of smaller proteins (< 29 kDa). As beta-actin mRNA, beta-tubulin mRNA and vimentin mRNA have been observed to occupy separate cytoplasmic locales, the proteins detected here may be operative both in binding mRNAs to the CSK in situ, as well as in localizing mRNA in the cytoplasm.

Liquid chromatographic analysis of amino acids: using dimethylamino-azobenzenesulfonyl chloride and Hypersil ODS column to analyze the composition of apo B peptides

A reliable high-performance liquid chromatography (HPLC) method is described for the separation of dimethylamino-azobenzenesulfonyl-amino acid (DABS-AA). The separation is accomplished by reversed-phase chromatography on a Hypersil ODS column (4.6 x 150 mm) with a Hewlett-Packard liquid chromatography system. In addition to the developed sample and solvent preparation procedure, this precolumn modification method using dimethylaminoazobenzene sulfonyl chloride (DABS-CL) for amino acid analysis is proved reliable and sensitive. Five apolipoprotein B-100 tryptic peptides, two of them containing cysteine, were demonstrated as examples for the general application of this method in amino acid analysis. It is a useful method for analysis of cysteine- and cystine-containing peptide and, furthermore, for determination of sulfhydryl and disulfide linkages of proteins.

Effects of intense antecedent sympathetic stimulation on sympathetic neurotransmission in the heart

We studied the effects of intense sympathetic stimulation on the chronotropic responses of the heart to subsequent test stimulations of the cardiac autonomic nerves in dogs anesthetized with alpha-chloralose. Such intense sympathetic stimulations (which we refer to as "release stimulations") are known to release neuropeptide Y as well as norepinephrine. The changes in cardiac cycle length evoked by vagal and sympathetic test stimulations were progressively more attenuated as we increased the frequency and duration of the antecedent sympathetic release stimulations. We found that 2.5 minutes after a maximal release stimulation (30 Hz for 5 minutes), the mean +/- SEM chronotropic responses to the vagal and sympathetic test stimulations were diminished to 36.5 +/- 1.6% and 54.7 +/- 1.3% respectively, of the prestimulation responses. The mean times for the chronotropic responses to the vagal and sympathetic test stimulations to recover to their control values were 52.0 +/- 1.3 and 63.2 +/- 2.9 minutes, respectively. This enduring effect suggests the action of a neuropeptide, such as neuropeptide Y. Phentolamine potentiated the inhibitory effects of the sympathetic release stimulations. The chronotropic responses to isoproterenol infusions were not affected appreciably by antecedent sympathetic release stimulation. We conclude, therefore, that the inhibitory effects of antecedent sympathetic release stimulation on cardiac sympathetic neurotransmission are mediated prejunctionally, probably via an inhibition of the neuronal release of norepinephrine by neuropeptide Y.

Analysis of vagally induced sinus arrhythmias

Vagal stimulation at precise times in successive cardiac cycles can elicit sinus arrhythmias. Two mechanisms have been identified that can, but do not necessarily, cause these vagally induced sinus arrhythmias. First, changes in cycle length elicited by a given concentration of acetylcholine (ACh) depend on the phase of the pacemaker cell action potential when the ACh binds to muscarinic receptors. Second, acetylcholinesterase degrades ACh rapidly enough for the mean concentration of ACh per cardiac cycle to vary from cycle to cycle. We used a mathematical model of the underlying cellular physiology, to examine whether these mechanisms are responsible for arrhythmogenesis. Computer simulation showed that both mechanisms contribute to the vagally induced sinus arrhythmias.

Electromechanical action of dofetilide and D-sotalol during simulated metabolic acidosis in isolated guinea pig ventricular muscle

We examined the electromechanical effects of two class III antiarrhythmic agents, dofetilide (UK-68,798) and D-sotalol, in acidic myocardium. Right ventricular papillary muscle preparations isolated from guinea pigs were divided into three groups (n = 6 per group): (a) drug-free, (b) dofetilide (10 nM), and (c) D-sotalol (30 microM). At normal extracellular pH (pH = 7.32 +/- 0.01), dofetilide and D-sotalol lengthened action potential duration (APD) to a similar extent, i.e., by 18-20%. Effective refractory period (ERP) increased in parallel, whereas membrane diastolic potential (MDP), action potential amplitude (APA), maximum velocity of depolarization (Vmax), and developed force (DF) were not significantly affected. Metabolic acidosis (pH = 6.78 +/- 0.01) was simulated by reducing the bicarbonate concentration of the Tyrode's solution from 20 to 6 mM. Superfusion with acidic solution alone for 30 min markedly decreased Vmax and DF, whereas APD and ERP were lengthened slightly. The acidosis-induced decreases in Vmax and DF were not affected by pretreatment with dofetilide or D-sotalol. In acidic superfusate, both agents still significantly increased APD and ERP to the same extent that they did at normal pH. The results indicate that metabolic acidosis, a major component of myocardial ischemia, does not attenuate the class III antiarrhythmic action of dofetilide and D-sotalol.

Class III antiarrhythmic action by potassium channel blockade: dofetilide attenuates hypoxia induced electromechanical changes

OBJECTIVE

The aim was to examine the electromechanical effects of dofetilide, a new class III antiarrhythmic agent, in isolated guinea pig ventricular muscle during hypoxia.

METHODS

Hypoxia was induced by superfusing guinea pig right ventricular papillary, muscles with Tyrode's solution gassed with 95% N2 + 5% CO2 [PO2 = 5.3(SEM 1.3) kPa]. Prior to hypoxia, the preparations were either pretreated for 30 min with 0.1 microM dofetilide (n = 6) or with 100 microM glibenclamide (a blocker of ATP sensitive K+ channels, n = 6), or not pretreated (n = 6). Sixteen additional preparations were exposed to 1 mM nicorandil (an activator of ATP sensitive K+ channels) in the absence (n = 6) and presence of dofetilide (n = 6) or glibenclamide (n = 4). Transmembrane action potentials and developed force were recorded using conventional microelectrode techniques and a force transducer.

RESULTS

During normoxia, dofetilide markedly increased APD90 from 236(SEM 6) ms to 298(7) ms (p < 0.05) and the effective refractory period (ERP) from 248(5) ms to 315(6) ms (p < 0.05). In the drug free group, 60 min hypoxia decreased APD90 by 47(5)% (p < 0.05), ERP by 48(4)% (p < 0.05) and developed force by 71(6)% (p < 0.05) of baseline, respectively. These hypoxia induced effects were significantly attenuated after pretreatment with dofetilide or glibenclamide. Nicorandil decreased APD90 by 45(5)% (p < 0.05), ERP by 44(6)% (p < 0.05), and developed force by 69(10)% (p < 0.05) of baseline, respectively. Pretreatment with dofetilide or glibenclamide also significantly attenuated the nicorandil induced decreases in APD90, ERP, and developed force.

CONCLUSIONS

Dofetilide, like glibenclamide, effectively attenuates hypoxia and nicorandil induced action potential shortening and the associated reduction in contractile force. Thus dofetidile would be expected to retain its antiarrhythmic efficacy during myocardial hypoxia or ischaemia.

Sequence of excitation as a factor in sympathetic-parasympathetic interactions in the heart

We determined the influence of differences in the time of initiation of sympathetic and vagal stimulation (both at 10 Hz) on the cardiac autonomic interactions in 16 open-chest anesthetized dogs. We always ended the concurrent sympathetic and vagal stimulations simultaneously. Sympathetic stimulation alone for 1 minute increased heart rate by 90 +/- 7 (mean +/- SEM) beats per minute, and vagal stimulation alone for 1 minute decreased heart rate by 67 +/- 5 beats per minute; i.e., the algebraic sum of these responses was an increase of 23 beats per minute. However, combined sympathetic and vagal stimulation for 1 minute actually decreased heart rate by 35 beats per minute; i.e., the vagal effects predominated. When vagal stimulation was initiated first, the chronotropic responses to combined stimulation were not significantly affected by the duration of antecedent vagal stimulation. However, when sympathetic stimulation was initiated first, the vagal predominance (disparity between the summated individual responses and the combined response) progressively diminished as we increased the duration of antecedent sympathetic stimulation. The vagal predominance diminished from a value of 67 +/- 21 beats per minute when the stimulations were initiated simultaneously to a value of 37 +/- 21 beats per minute when the duration of antecedent sympathetic stimulation was 10 minutes. Sympathetic stimulation releases not only norepinephrine but also neuropeptide Y, and this neuropeptide inhibits vagal neurotransmission. Our data suggest, therefore, that the longer the antecedent sympathetic stimulation, the greater the inhibition of vagal neurotransmission (presumably by the neuropeptide Y) and, therefore, the less pronounced the vagal predominance.

Effects of altered extracellular potassium and pacing cycle length on the class III antiarrhythmic actions of dofetilide (UK-68,798) in guinea-pig papillary muscle

The effects of altered extracellular K+ concentrations ([K+]o) and pacing cycle lengths (CLs) on the electrophysiological actions of dofetilide (UK-68,798), a potent class III antiarrhythmic agent, were examined in isolated guinea-pig ventricular papillary muscle. At a normal [K+]o (4 mM) and at CL between 300 and 5000 msec, dofetilide (10 nM) significantly increased the action-potential duration (APD) and the effective refractory period (ERP), whereas other action-potential parameters were unaffected. Elevation of [K+]o to 10 mM reduced membrane diastolic potential (MDP), action-potential amplitude (APA), and the maximum rising velocity of the action-potential upstroke (Vmax). These changes were accompanied by a small shortening of APD90, but with an increase in ERP; i.e., the ERP/APD90 ratio was increased. Dofetilide also significantly lengthened APD90 at 10 mM [K+]o and at each CL. Even at the short cycle lengths (300 and 500 msec), dofetilide-induced increases in APD90 were not attenuated whether [K+]o was at 4 or 10 mM. These results indicate that at various pacing CLs, 10 nM dofetilide increases myocardial APD and ERP to a similar extent without significant reverse use-dependence when the cell membrane is normally polarized or partially depolarized by elevated [K+]o. Dofetilide may, therefore, be expected to be beneficial in the treatment of cardiac tachyarrhythmias related or unrelated to regional myocardial hyperkalemia during myocardial ischemia.

Class III antiarrhythmic action and inotropy: effects of almokalant in acute ischaemic heart failure in dogs

We studied the haemodynamic and metabolic effects of the novel class III antiarrhythmic agent almokalant (H 234/09) in acute ischaemic heart failure at a dose prolonging ventricular repolarization. In pentobarbital anaesthetized dogs, heart failure was induced by microembolization of the area supplied by the main left coronary artery until a stable left ventricular end-diastolic pressure (LVEDP) of 32 +/- 2 mmHg was achieved. Embolization depressed LV dP/dt(max), LV dP/dt(min), left ventricular systolic pressure (LVSP) and cardiac output. After intravenous infusion of almokalant (0.35 micrograms/kg) LV dP/dt(max) and LV dP/dt(min) were not significantly changed at paced cycle length of 300 msec., whereas LVSP and aortic pressure decreased both at spontaneous and paced cycle length of 300 msec. LVEDP remained unchanged. Heart rate decreased from 185 +/- 7 to 167 +/- 5 beats/min., and corrected QT-time (QTc) increased from 9.5 +/- 0.3 to 10.4 +/- 0.5 msec. Arterial concentration and net myocardial uptake of glucose, lactate and free fatty acids were not significantly influenced by almokalant. In conclusion, almokalant at a dose prolonging ventricular repolarization had no negative inotropic effect in acute ischaemic heart failure.

Class III antiarrhythmic action and inotropy: effects of dofetilide in acute ischemic heart failure in dogs

We studied the hemodynamic and metabolic effects of the novel class III antiarrhythmic agent dofetilide (UK-68,798) in acute ischemic heart failure. In pentobarbital-anesthetized dogs, heart failure was induced by microembolization of the area supplied by the main left coronary artery until a stable left ventricular (LV) end-diastolic pressure of 27 +/- 2 mm Hg was achieved. Embolization depressed LV systolic pressure, LV dP/dtmax, LV dP/dtmin, and cardiac output. None of these parameters were changed following i.v. infusion of dofetilide 5, 10, or 25 micrograms/kg, during spontaneous and paced cycle length of 300 ms (n = 9). Heart rate decreased by 12 +/- 8, 19 +/- 7, and 21 +/- 7 beats/min (p less than 0.05), while QT time increased by 23 +/- 7, 33 +/- 9, and 40 +/- 10 ms (p less than 0.05) after 5, 10, and 25 micrograms/kg, respectively. Ventricular effective refractory period increased from 128 +/- 10 to 153 +/- 11 ms after 25 micrograms/kg (n = 4). Arterial concentration and net myocardial uptake of glucose, lactate, and free fatty acids were not significantly influenced by dofetilide. In conclusion, dofetilide, at doses that prolonged repolarization, was devoid of cardiodepressive effects in acute ischemic heart failure.

Stabilities and properties of multilinked hemoglobins

Crosslinking of both human and dog hemoglobin has been done with a variety of reagents to produce singly, doubly and multiply crosslinked hemoglobins. Succinate and glutarate diaspirins did not crosslink deoxy human hemoglobin in good yield, in contrast to the fumarate analog (DBSF). Deoxy dog Hb did not react well with DBSF, but oxy dog Hb did react, giving crosslinked tetramers as well as dimers on SDS electrophoresis. Crosslinking with a short, rigid reagent (difluorodinitrobenzene) resulted in a similar product for both oxy and deoxy hemoglobin that had high stability and oxygen affinity. The trilinker, tris-chloroethylamine, produced a more stable product than the corresponding crosslinker, bis-chloroethylamine. Double crosslinking oxy Hb with DBSF and dimethylpimelimidate or with DBSF followed by deoxygenation and recrosslinking with DBSF gave products with higher denaturation temperatures. The diaspirin double crosslinked product had high oxygen affinity.

[Clinical study of superoxide dismutase in recurrent aphthous ulceration]

Activity of superoxide dismutase (SOD) was determined in erythrocytes obtained from 74 patients with recurrent aphthous ulcerations (RAU) and 100 healthy individuals. The results showed that activity level of SOD in RAU was significantly lower as compared with that in the controls (P less than 0.01). The activity of SOD in 30 cases of RAU at interval period was elevated on reexamination, but it was still lower than that in the controls (P less than 0.01). There is evidence that damage of superoxide radicals (O.2) and decrease of activity of SOD may play important roles in the pathogenesis of RAU. A random double-blind, placebo-controlled, cross-over trial on membrane SOD was carried out in 40 patients with RAU. The results demonstrated that the effective rate of SOD was 90%, being markedly higher than that of placebo. It is suggested that membrane SOD, as a topical medicine, could increase the concentration of SOD on the ulcerous surfaces, prevent O.2-induced injury, decrease capillary permeability, relieve inflammation and improve cure of ulcer.

Negative chronotropic effect of a novel class III antiarrhythmic drug, UK-68,798, devoid of beta-blocking action on isolated guinea-pig atria

1. The chronotropic effects of a novel class III antiarrhythmic drug, UK-68,798, and the beta-adrenoceptor blocker, propranolol, for comparison, were studied on spontaneously beating right atria isolated from guinea-pigs in the absence and presence of increasing concentrations of isoprenaline (10(-10)-10(-4) M). 2. UK-68,798 (10(-9)-10(-5) M) decreased spontaneous atrial rate by 6-21%. Propranolol (10(-8) -10(-6) M) also had a negative but significantly smaller chronotropic effect. 3. UK-68,798 dose-dependently reduced the maximal positive chronotropic effect induced by isoprenaline, but without significantly shifting the concentration-response curve for isoprenaline in a parallel fashion. A pD'2 value of 5.88 was obtained. As expected, propranolol displayed a competitive inhibition with a pA2 value of 8.21. 4. The results demonstrate a negative chronotropic effect of UK-68,798, which is not associated with a beta-adrenoceptor blocking action. We suggest that the negative chronotropic effect is linked with potassium channel blockade and thereby the class III antiarrhythmic action of UK-68,798.

Changes in the baroreceptor reflex at the start of muscle contraction in the decerebrate cat

1. The action of muscle contraction on the sensitivity of the cardiac vagal component of the baroreceptor reflex was examined in decerebrate cats. 2. The sensitivity of the baroreceptor reflex was expressed as the difference between the maximum prolongation of the R-R interval in response to carotid sinus baroreceptor stimulation and the mean of ten R-R intervals immediately before carotid sinus pressure elevation. 3. Muscle contraction elicited by electrical stimulation of L7 ventral roots (50 Hz) significantly reduced the sensitivity of the baroreceptor reflex by reducing the prolongation of the R-R interval from 269 +/- 31 to 159 +/- 22 ms. 4. Inhibition of the cardiac vagal component of the baroreceptor reflex was seen just 1 s after the onset of contraction and with stimulation frequencies as low as 10 Hz. 5. These results show for the first time that changes in the sensitivity of the baroreceptor reflex during exercise result in part from afferent information originating in the contracting muscles.

Inhibition of cardiac vagal component of baroreflex by group III and IV afferents

The action of electrically evoked activity in somatic afferent fibers on the sensitivity of the baroreceptor reflex was examined in decerebrate cats. The sensitivity of the reflex was expressed as the difference between the maximum prolongation of R-R interval in response to carotid sinus pressure elevation and the mean of 10 R-R intervals immediately before pressure elevation. The control value of R-R interval prolongation was 192 +/- 50 ms. Stimulation (10 Hz) of group I and II fibers of the right peroneal nerve (evoked volleys recorded from the sciatic nerve) had no effect on R-R interval prolongation (171 +/- 45 ms). Recruitment of group III fibers (10 Hz) conducting at 23.6 +/- 0.65 m/s reduced the prolongation of R-R interval to 52 +/- 14 ms. Recruitment of group IV fibers (10 Hz) conducting less than 2.5 m/s further reduced the prolongation of R-R interval to 1.0 +/- 8.0 ms. It is concluded that the inhibition of the cardiac vagal component of the baroreceptor reflex produced by electrical stimulation of the peroneal nerve is mediated by afferent fibers of groups III and IV.

Stimulated four-photon mixing with crossed pump dividing in an optical fiber

An experimental study of stimulated four-photon mixing with crossed pump dividing in a birefringent optical fiber is described. The interactive four photons are all in the same mode but with different polarizations. The pump wave is distributed in two orthogonal linear polarizations, and the polarizations of Stokes and anti-Stokes waves are also orthogonal. It is shown that the Stokes shift of this stimulated four-photon mixing process is related not only to the material dispersion but also to the waveguide dispersion and is directly proportional to the birefringence.

Rate-dependent class III antiarrhythmic action, negative chronotropy, and positive inotropy of a novel Ik blocking drug, UK-68,798: potent in guinea pig but no effect in rat myocardium

The electromechanical effects of UK-68,798 (UK), a novel class III antiarrhythmic drug, were studied in guinea pig and rat papillary muscles (PMs) and atria in vitro using conventional microelectrode technique. UK (10(-8)-10(-6) M) prolonged the action potential duration (APD) by 21-58% and effective refractory period in parallel, without affecting the resting potential or maximum rate of depolarization in guinea pig PM stimulated at 1 Hz. UK increased the contractile force without prolonging the time to peak force or relaxation. In comparison, 5 x 10(-5) M d-sotalol was needed to induce the same electrophysiological effects as 10(-8) M UK. UK prolonged the APD significantly less at 2 Hz than at 1 and 0.5 Hz. Early afterdepolarizations (EADs) developed in 2 of 11 preparations after 10(-6) M at 0.5 Hz. No reversal of drug effect was seen after up to 2 h washout. UK (10(-9)-10(-5) M) reduced the spontaneous heart rate and prolonged the sinus node recovery time of guinea pig right atria. No effects on rat PM or atria, even after 10(-5) M, indicate a selective action of UK on the delayed rectifying outward potassium current, Ik. These results indicate a potent and selective, rate-dependent class III antiarrhythmic action of UK-68,798 linked with positive inotropy. Increased APD, bradycardia, and induction of EADs, however, represent a potential arrhythmogenic combination.

A simple method for estimating association constants between monoclonal antibodies and derivatized or native antigens

We describe a simple method for estimating the association constant between an antibody and an antigen, based on a theoretical treatment of experimental dose-response data. We used this method to calculate the association constants of an anti-progesterone monoclonal antibody for native progesterone and for progesterone 11 alpha-hemisuccinate. These association constants provide a quantitative measure of the bridging-group recognition by the antibody.

A simple method for estimating association constants between monoclonal antibodies and derivatized or native antigens

We describe a simple method for estimating the association constant between an antibody and an antigen, based on a theoretical treatment of experimental dose-response data. We used this method to calculate the association constants of an anti-progesterone monoclonal antibody for native progesterone and for progesterone 11 alpha-hemisuccinate. These association constants provide a quantitative measure of the bridging-group recognition by the antibody.

Assessing symptom change in Southeast Asian refugee survivors of mass violence and torture

The authors evaluated changes in symptoms and levels of perceived distress of 21 Cambodian, 13 Hmong/Laotian, and 18 Vietnamese patients before and after a 6-month treatment period. Most of the patients improved significantly. Cambodians had the greatest and Hmong/Laotians had the least reductions in depressive symptoms. Although psychological symptoms improved, many somatic symptoms worsened. The authors conclude that refugee survivors of multiple traumata and torture can be aided by psychiatric care. They recommend investigations with larger samples and suitable control groups to further clarify the relative contributions of trauma, diagnosis, and acculturation stress to treatment outcome.

[Ultracytochemical studies on glycosaminoglycans during early corneal development in Bufo raddei]

Glycosaminoglycans (GAGs) and their changes in early corneal development of Bufo raddei Strauch (from stage 16, neural tube, to stage 25, operculum completely closed) were studied with electron microscopic cytochemical method. Results show that synthesis of GAGs changes from non-sulfated to sulfated, and its content increased gradually with the development of cornea. Hyaluronic acid (HA) in each part of cornea begins to increase gradually from stage 16 to 21 (mouth open stage), with its peak at stage 20 (gill circulation stage) to 21, then decreases. In the mean time, contents of dermatam sulfate (DS), chondroitin sulfate (CS), heparan sulfate (HS) and heparin (Hep) increase gradually. It is considered that HA, HS and collagen may be related to the migration of mesenchymal cells, and HA promotes the expansion and hydration of corneal stroma; sulfated GAGs are correlated with dehydration of cornea, cell density and corneal transparency; DS, CS, HS and Hep deposited among collagen fibrils could adjust their arrangement. All these changes would enhance transparency of cornea.