Defective major histocompatibility complex class II assembly, transport, peptide acquisition, and CD4+ T cell selection in mice lacking invariant chain expression

We used gene targeting techniques to produce mice lacking the invariant chain associated with major histocompatibility complex (MHC) class II molecules. Cells from these mice show a dramatic reduction in surface class II, resulting from both defective association of class II alpha and beta chains and markedly decreased post-Golgi transport. The few class II alpha/beta heterodimers reaching the cell surface behave as if empty or occupied by an easily displaced peptide, and display a distinct structure. Mutant spleen cells are defective in their ability to present intact protein antigens, but stimulate enhanced responses in the presence of peptides. These mutant mice have greatly reduced numbers of thymic and peripheral CD4+ T cells. Overall, this striking phenotype establishes that the invariant chain plays a critical role in regulating MHC class II expression and function in the intact animal.

Beta-adrenergic agonists that down-regulate receptor mRNA up-regulate a M(r) 35,000 protein(s) that selectively binds to beta-adrenergic receptor mRNAs

In an effort to explore the molecular basis for agonist-induced destabilization of beta-adrenergic receptor mRNA, we investigated the nature of RNA-binding proteins both in untreated and agonist-treated DDT1-MF2 smooth muscle cells. Messenger RNAs for the alpha 1b-, beta 1-, and beta 2-adrenergic receptors as well as for beta-globin were transcribed in vitro, incubated with cytosolic fractions, covalently cross-linked by short-wave UV light, and analyzed by SDS-polyacrylamide gel electrophoresis. A prominent M(r) 35,000 radiolabeled protein(s) with the following characteristics was identified: (i) binds selectively to beta 1- and beta 2-adrenergic receptor mRNAs, both of which undergo agonist-induced down-regulation; (ii) does not bind to either alpha 1b-adrenergic receptor mRNA, which does not undergo agonist induced down-regulation, or to beta-globin mRNA; (iii) displays binding to beta 2-adrenergic receptor mRNA that is selectively competed by poly(U) RNA, but not poly(A), -(C), or -(G) RNA; and (iv) displays binding to receptor mRNA that can be competed by RNA harboring destabilizer sequences that are AU-rich and AUUUA pentamer-rich. The abundance of the M(r) 35,000 RNA-binding protein selective for beta-adrenergic receptor message, a factor we term beta ARB protein, varies inversely with the level of receptor mRNA, being induced by agonists that down-regulate receptor mRNA.

Protein kinase C reduces Mg2+ block of NMDA-receptor channels as a mechanism of modulation

The roles of N-methyl-D-aspartate (NMDA) receptors and protein kinase C (PKC) are critical in generating and maintaining a variety of sustained neuronal responses. In the nociceptive (pain-sensing) system, tissue injury or repetitive stimulation of small-diameter afferent fibres triggers a dramatic increase in discharge (wind-up) or prolonged depolarization of spinal cord neurons. This central sensitization can neither be induced nor maintained when NMDA receptor channels are blocked. In the trigeminal subnucleus caudalis (a centre for processing nociceptive information from the orofacial areas), a mu-opioid receptor agonist causes a sustained increase in NMDA-activated currents by activating intracellular PKC. There is also evidence that PKC enhances NMDA-receptor-mediated glutamate responses and regulates long-term potentiation of synaptic transmission. Despite the importance of NMDA-receptors and PKC, the mechanism by which PKC alters the NMDA response has remained unclear. Here we examine the actions of intracellularly applied PKC on NMDA-activated currents in isolated trigeminal neurons. We find that PKC potentiates the NMDA response by increasing the probability of channel openings and by reducing the voltage-dependent Mg2+ block of NMDA-receptor channels.

MHC class II interaction with CD4 mediated by a region analogous to the MHC class I binding site for CD8

Interactions between major histocompatibility complex (MHC) molecules and the CD4 or CD8 coreceptors have a major role in intrathymic T-cell selection. On mature T cells, each of these two glycoproteins is associated with a class-specific bias in MHC molecule recognition by the T-cell receptor. CD4+ T cells respond to antigen in association with MHC class II molecules and CD8+ T cells respond to antigen in association with MHC class I molecules. Physical interaction between the CD4/MHC class II molecules and CD8/MHC class I molecules has been demonstrated by cell adhesion assay, and a binding site for CD8 on class I has been identified. Here we demonstrate that a region of the MHC class II beta-chain beta 2 domain, structurally analogous to the CD8-binding loop in the MHC class I alpha 3 domain, is critical for function with both mouse and human CD4.

Quantitative measurement of muscle and subcutaneous fat thickness in newborn by real-time ultrasonography: a useful method for site and depth evaluation in vaccination

In order to quantify muscle thickness and choose the appropriate site for intramuscular injection of vaccines in neonates, we used ultrasonography to measure muscle and subcutaneous fat thickness of anterolateral mid-thigh, upper outer quadrant of buttock and middle area of deltoid in fifty full term (group 1) and thirty low birth weight (group 2) infants. A Hitachi EUB40 real-time scanner and a 5 MHz transducer was used in the study. We delineated the normal distribution of muscle and subcutaneous fat thickness in mid-thigh, buttock and deltoid areas of full term and low birth weight infants. There was no significant difference between male and female infants in the two groups. Muscle and subcutaneous fat thickness in the thigh area was 11.8 +/- 1.9 mm and 3.8 +/- 0.4 mm, respectively, in group 1; 8.6 +/- 1.7 mm and 2.7 +/- 0.5 mm in group 2. Figures in the buttock area were 10. 1 +/- 1.5 mm and 3.7 +/- 0.5 mm in group 1, 6.9 +/- 1.2 mm and 2.7 +/- 0.7 mm in group 2; and in the deltoid area were 5.2 +/- 0.7 mm and 3.4 +/- 1.5 mm in group 1 and 3.8 +/- 0.8 mm and 2.3 +/- 0.6 mm in group 2. There was significant logarithmic correlation between muscle thickness and body weight (r = 0.6, 0.8, 0.6) and muscle thickness and body length (r = 0.4, 0.6, 0.6) in thigh, buttock and deltoid areas of the low birth weight infants. In contrast, there was significant logarithmic correlation only between buttock muscle and body weight (r = 0.5) in the full term infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Voltage-dependent tetrodotoxin binding to single batrachotoxin-modified Na channels recorded from intact neuroblastoma cells

To clarify the voltage-dependent actions of tetrodotoxin (TTX) on Na channels in cellular membranes, we examined the TTX block of single batrachotoxin-modified Na channels in neuroblastoma cells. We found these Na channels had a high affinity for TTX which decreased e-fold per 35.5 mV depolarization. The decrease in affinity resulted primarily from a decrease in the blocking rate for TTX; the unblocking rate increased slightly with depolarization. While the voltage-dependence of TTX binding to neuroblastoma Na channels was similar to that reported in purified Na channels incorporated in bilayers, the magnitude and voltage-dependence of the rate constants were quite different.

Sustained potentiation of NMDA receptor-mediated glutamate responses through activation of protein kinase C by a mu opioid

mu opioids, such as morphine and certain enkephalin analogs, are known to modulate glutamate-evoked activity in dorsal horn neurons in the spinal cord and caudal brain stem. Yet the molecular mechanism by which this modulation occurs is not understood. We examined the interactions between glutamate and a selective mu opioid receptor agonist, D-Ala2-MePhe4-Gly-ol5-enkephalin (DAGO), in spinal trigeminal neurons in thin medullary slices of rats. DAGO caused a sustained increase in glutamate-activated currents that are mediated by N-methyl-D-aspartate receptors. Intracellularly applied protein kinase C (PKC) mimics the effect of DAGO, and a specific PKC inhibitor interrupts the sustained potentiation produced by DAGO. Thus, PKC plays a key role in mediating the action of mu opioid peptides.

Block of kainate receptor channels by Ca2+ in isolated spinal trigeminal neurons of rat

Compared with N-methyl-D-aspartate-activated channels, the interaction of Ca2+ with kainate-activated or with quisqualate-activated channels is not well understood. We have studied the effect of Ca2+ on kainate-activated currents in isolated trigeminal neurons and found that Ca2+ inhibits kainate responses. This inhibition occurs not because Ca2+ changes the affinity of kainate to its receptor, but because Ca2+ blocks monovalent cation permeation through kainate-activated channels. This Ca2+ block gives rise to the outward rectification of the kainate responses.

Modulation of glycine receptor chloride channels by cAMP-dependent protein kinase in spinal trigeminal neurons

Glycine is an important inhibitory transmitter in the brainstem and spinal cord. In the trigeminal subnucleus caudalis (medullary dorsal horn) and in the spinal dorsal horn (the relaying centres for processing pain and sensory information), glycine inhibits the glutamate-evoked depolarization and depresses firing of neurons. The binding of glycine to its receptor produces a large increase in Cl- conductance, which causes membrane hyperpolarization. The selectivity and gating properties of glycine receptor channels have been well characterized; the glycine receptor molecules have also been purified. The amino-acid sequence, deduced from complementary DNA clones encoding one of the peptides (the 48K subunit), shows significant homology with gamma-aminobutyric acid A (GABAA) and nicotinic acetylcholine receptor subunits, suggesting that glycine receptors may belong to a superfamily of chemically gated channel proteins. However, very little is known about the modulation of glycine receptor channels. We have investigated the regulation of strychnine-sensitive glycine receptor channels by cyclic AMP-dependent protein kinase in neurons isolated from spinal trigeminal nucleus of rat and report here that the protein kinase A dramatically increased the glycine-induced Cl- currents by increasing the probability of the channel openings. GS protein, which is sensitive to cholera toxin, was involved in the modulation.

Effect of monovalent measles and trivalent measles-mumps-rubella vaccines at various ages and concurrent administration with hepatitis B vaccine

To determine the most suitable vaccination schedule in developing countries, a study was conducted to reevaluate the immunogenicity of monovalent measles vaccine and trivalent measles-mumps-rubella vaccine at different ages. The success rate of measles vaccination was 84% at 9 months, 88% at 12 months and 100% at 15 months of age. Vaccination with measles vaccines at 9 and 15 months of age was also 96% immunogenic. Most vaccinees (16 of 17) not responding to the first measles vaccine before 1 year of age developed measles antibody with another shot of vaccine after 15 months of age. Trivalent measles-mumps-rubella vaccine worked well in children ages 14 to 18 months. Administering trivalent vaccine and hepatitis B vaccine concurrently at 1 year of age, rubella and mumps antibodies developed in more than 95% of vaccinees, while measles antibody was detected in 88%. Responses to hepatitis B vaccine in this situation were good; 89% of vaccinees developed antibody against hepatitis B surface antigen (greater than or equal to 10 mIU/ml) and the geometric mean titer was 362.49 mIU/ml. In summary vaccination twice at 9 and 15 months is effective and is a useful regimen in developing countries where measles is still endemic. Trivalent vaccine and hepatitis B vaccine will not interfere with each other when given together at 1 year of age.

Ionic currents in retrogradely labeled trigeminothalamic neurons in slices of rat medulla

We have recorded the ionic currents of identified trigeminothalamic neurons in medulla slices in vitro. Trigeminothalamic cells were first retrogradely labeled by injecting fluorescent latex microspheres in the thalamus of a 7- to 10-day-old rat. Two days later, thin slices (80-100 microns) were prepared from the lower medulla of the injected rat. Whole cell recordings were performed on the labeled cells located in the spinal trigeminal nucleus caudalis using the patch clamp technique. The voltage dependent inward sodium, inward calcium and outward potassium currents are qualitatively similar to those obtained from the enzymatically dissociated trigeminothalamic neurons. Successful application of this thin slice method opens the opportunity of studying synaptic circuitry in the trigeminothalamic system.

[Existence of phencyclidine receptor in guinea pig atria]

[3H]-PCP was used in receptor binding studies on membrane preparation from guinea pig atria. It was found that this binding was specific, saturable, reversible and stereoselective. Scatchard plots revealed that guinea pig atria had two different affinity binding sites. The high affinity constant (Kd1) and low affinity constant (Kd2) were 12.15 +/- 0.414 nmol/l and 561.23 +/- 121.36 nmol/l, respectively; the maximum bindings (Bmax) were 0.71 +/- 0.029 pmol/mg protein (Bmax1) and 1.047 +/- 0.099 pmol/mg protein (Bmax2), respectively. The displacement analysis revealed that the [3H]-PCP binding was inhibited by the ligands of both PCP and sigma receptors, while the inhibition of PCP ligands was larger than of sigma ligands. Etorphine, an agonist of opioid receptors, failed to inhibit the binding of [3H]-PCP. The results mentioned above show the existence of a specific PCP receptor in guinea pig atria. The autoradiographic analysis of guinea pig right atria was shown that there was autoradiographic localization of [3H]-PCP on atria of guinea pig with homogeneous distribution, suggesting that the distribution of PCP receptor in atria was homogeneous relatively.

First isolation of Legionella gormanii in China

The first strain of non-Legionella pneumophila, L-88-1, was isolated from some condensed water in a steam discharge pipe extending from a boiler in China. The organism was characterized by serologic, biochemical, DNA hybridization and electron microscopic studies. It was identified to be L. gormanii.

Origin of thalamically projecting somatosensory relay neurons in the immature rat

The locations of spinothalamic (STT) and trigeminothalamic (TTT) neurons in 14-18-day rats using retrograde transport of fluorescent latex microspheres were examined. The aim of this study was to determine whether the connections between the somatosensory relay neurons and the thalamus were established in these immature rats. The majority of the labeled STT and TTT neurons was found in the brainstem and upper cervical cord (C1-C4). These cells were distributed to a number of distinct groups. Among them, the nucleus of trigeminal spinal tract interpolaris (SP51) had the highest number of TTT cells, and the internal basilar nucleus (IB) comprised the largest population of STT cells. Except for the cells located in the dorsal portion of the ventral horn (VHd), most of the labeled STT and TTT cells were contralateral to the thalamic injection sites. This pattern of distribution of the projecting neurons in immature rats is very similar to the pattern observed in adult rats. The development of the STT and TTT projections in 14-18-day rats is therefore largely complete. This result will allow us to extrapolate our understanding of the membrane properties of projection cells obtained in the immature rats to the adult rats.

Calcium channels in isolated rat dorsal horn neurones, including labelled spinothalamic and trigeminothalamic cells

1. Single isolated neurones were prepared from the spinal trigeminal nucleus and the dorsal horn of cervical spinal cord of the rat. Spinothalamic and trigeminothalamic neurones were identified using rhodamine-labelled fluorescent latex microspheres. 2. Calcium currents in these cells were examined by the whole-cell patch-clamp technique. Three types of calcium currents, transient (T) and slow inactivating (N and L) types, were identified by their sensitivities to inorganic blockers and rates of inactivation at two different holding potentials (temperature = 21-25 degrees C). 3. From a holding potential of -100 mV, the ICa,T began to activate at -60 mV. The current reached its maximum amplitude around -30 mV and was inactivated completely when the cell was held more positive than -60 mV. The time constant of the inactivation was between 10 and 50 ms. 4. The slow inactivating component of ICa was dissociated into two components by eliciting ICa from two holding potentials of -100 and of -40 mV. The current (ICa,L) activated from -40 mV was characterized by positive activation potentials and a very slow inactivation (time constant, 700-4000 ms). The current (ICa,N) elicited from a holding potential of -100 mV started to activate at -30 mV and inactivated slowly with time constants ranging between 400 and 1000 ms. 5. Compared with the ICa,T, the inactivation curve for ICa,N was shifted about 30 mV in the depolarizing direction. ICa,N inactivated over a broader range of potentials, and its inactivation and activation curves overlapped. 6. Cadmium blocked ICa,T at a concentration 24 times higher than that which was needed to block slow inactivating currents. The apparent dissociation constant of nickel for ICa,T is twofold lower than that for the slow inactivating currents. 7. Nimodipine (2 microM) decreased the slow inactivating currents, but had no effect on ICa,T. (-)-Bay K 8644 (200 nM) increased both ICa,N and ICa,L and shifted the current activation in the hyperpolarizing direction. This result is different from that obtained in sensory and sympathetic neurones in which ICa,N is insensitive to Bay K 8644.

Electrical properties of acutely isolated, identified rat spinal dorsal horn projection neurons

We used a retrograde marker, rhodamine-labeled fluorescent latex microspheres and the enzyme papain to isolate a group of identified, dorsal horn projection neurons from rat spinal cord. This method has allowed us to study the electrical properties of these acutely dissociated cells with patch-clamp techniques. It will also provide us the opportunity to understand the transmitter responses of these neurons that had not undergone culturing manipulation. The isolated projection cells have a short-lasting action potential and fire repetitively under a sustained depolarization. The ionic conductance mechanisms underlying the action potentials were studied under voltage-clamp conditions. Voltage-dependent inward sodium, inward calcium, outward potassium and calcium-activated potassium currents were observed in these cells.

The properties of batrachotoxin-modified cardiac Na channels, including state-dependent block by tetrodotoxin

Batrachotoxin (BTX) modification and tetrodotoxin (TTX) block of BTX-modified Na channels were studied in single cardiac cells of neonatal rats using the whole-cell patch-clamp recording technique. The properties of BTX-modified Na channels in heart are qualitatively similar to those in nerve. However, quantitative differences do exist between the modified channels of these two tissues. In the heart, the shift of the conductance-voltage curve for the modified channel was less pronounced, the maximal activation rate constant, (tau m)max, of modified channels was considerably slower, and the slow inactivation of the BTX-modified cardiac Na channels was only partially abolished. TTX blocked BTX-modified mammalian cardiac Na channels and the block decreased over the potential range of -80 to -40 mV. The apparent dissociation constant of TTX changed from 0.23 microM at -50 mV to 0.69 microM at 0 mV. No further reduction of block was observed at potentials greater than -40 mV. This is the potential range over which gating from closed to open states occurred. These results were explained by assuming that TTX has a higher affinity for closed BTX-modified channels than for open modified channels. Hence, the TTX-binding rate constants are considered to be state dependent rather than voltage dependent. This differs from the voltage dependence of TTX block reported for BTX-modified Na channels from membrane vesicles incorporated into lipid bilayers and from amphibian node of Ranvier.

Ahpatinins, new acid protease inhibitors containing 4-amino-3-hydroxy-5-phenylpentanoic acid

A soil isolate, Streptomyces sp. WK-142, was found to produce new acid protease inhibitors, ahpatinins A, B, D, E, F and G active against pepsin and renin. Ahpatinin C was found to be identical with pepstatin A. The structure determinations were based on mass spectral data. Four of the compounds contain the unusual amino acid, 4-amino-3-hydroxy-5-phenylpentanoic acid as a building component.

Identification of spinothalamic tract cells in fresh, unfixed rat spinal cord

Diamidino yellow dihydrochloride (DY . 2HCl) can reliably label spinothalamic tract cells both in the perfused, fixed and in the fresh, unfixed rat spinal cord. The major advantages of DY . 2HCl as a retrograde marker are that it leaks from the cells very slowly and can be conveniently identified in unfixed neurons by fluorescence microscopy. DY . 2HCl will be a useful marker for identification of spinothalamic tract cells that are to be studied in vitro.

Simulatory hypothyroidism pituitary function in vitro: dynamics of TSH release after TRH stimulation in perifused rat hemipituitaries

The production of immunoreactive TSH by hemipituitaries (Hps) to the stimulation of TRH in perifusion with negligible influence of the feedback of secretogogues and hormones was analysed. The stimulations were of long term continuous (3 hrs) and short term (15 min), with the dose levels of 1, 10 and 100 ng per ml of medium (for 3 hrs) or in 2 ml (for 15 min). The largest amount in production and the fastest rate in release of TSH found in present report is at 10 ng level. Only total TSH, in tissue plus in medium, after continuous TRH stimulation were dose-related, but not in release alone. We present herein an analysis of pituitary TSH production, in a perifusion system under steady TRH stimulation. This arrangement is believed to be a condition simulating hypothyroidism in pituitary level and suitable for study of the functions of the pituitary with hyperactivated thyrotrophs.

Gating kinetics of batrachotoxin-modified sodium channels in neuroblastoma cells determined from single-channel measurements

We have observed the opening and closing of single batrachotoxin (BTX)-modified sodium channels in neuroblastoma cells using the patch-clamp method. The conductance of a single BTX-modified channel is approximately 10 pS. At a given membrane potential, the channels are open longer than are normal sodium channels. As is the case for normal sodium channels, the open dwell times become longer as the membrane is depolarized. For membrane potentials more negative than about -70 mV, histograms of both open-state dwell times and closed-state dwell times could be fit by single exponentials. For more depolarized potentials, although the open-state histograms could still be fit by single exponentials, the closed-state histograms required two exponentials. This data together with macroscopic voltage clamp data on the same system could be accounted for by a three-state closed-closed-open model with transition rates between these states that are exponential functions of membrane potential. One of the implications of this model, in agreement with experiment, is that there are always some closed BTX-modified sodium channels, regardless of membrane potential.

Batrachotoxin modifies the gating kinetics of sodium channels in internally perfused neuroblastoma cells

We have studied the effects of batrachotoxin (BTX) on sodium channels in hybrid mouse neuroblastoma cells NG108-15 by using the suction pipet voltage clamp method. BTX-modified sodium channels activate with first-order kinetics and, over most of the potential range, activate more slowly than normal sodium channels. The peak conductance-voltage curve and the time constant of activation-versus-voltage curve for BTX-modified sodium channels are shifted about 50 mV in the hyperpolarizing direction compared to the corresponding curves for normal sodium channels. There is no change in the slope of the conductance-voltage curve. These results suggest that BTX slows down one of the steps leading to channel opening, which consequently becomes rate-limiting. In addition, BTX eliminates both fast and slow inactivation.