Contribution of a slowly inactivating potassium current to the transition to firing of neostriatal spiny projection neurons

1. Neostriatal spiny projection neurons display a prominent slowly depolarizing (ramp) potential and long latency to spike discharge in response to intracellular current pulses. The contribution of a slowly inactivating A-current (IAs) to this delayed excitation was investigated in a neostriatal slice preparation using current pulse protocols incorporating information based on the known voltage dependence, kinetics, and pharmacological properties of IAs. 2. Depolarizing intracellular current pulses evoked a slowly developing ramp potential that could last for seconds without reaching steady state and continued until either the pulse was terminated or spike threshold was reached. The slope of the ramp potential was dependent on the level of depolarization achieved by the membrane, and the apparent activation threshold for this ramp depolarization was approximately -65 mV. 3. Application of low concentrations of 4-aminopyridine (4-AP, 30-100 microM) or dendrotoxin (DTX, 30 nM), which are known to selectively block IAs, reduced both the slope of the ramp potential and the latency to first spike discharge. As has been described previously, blockade of inward Na+ and Ca2+ currents with tetrodotoxin (TTX, 1 microM) and cadmium (400 microM) also reduced the slope of the ramp depolarization. 4. A conditioning-test pulse protocol was used to examine the voltage dependence of inactivation of the ramp potential and long first spike latency. In the absence of a conditioning pulse, the test pulse evoked a slowly rising ramp potential and a spike with a long latency to discharge. A conditioning depolarization to approximately -60 mV decreased the slope of the ramp potential and the latency to first spike discharge evoked by the test pulse. A conditioning hyperpolarization to potentials below -100 mV, increased first spike latency. Application of a low concentration of 4-AP (100 microM) abolished the influence of prior membrane potential on the slope of the ramp depolarization and the latency to first spike discharge. 5. The kinetics of recovery from inactivation of the 4-AP-sensitive current were studied in the presence of TTX and cadmium by depolarizing cells to approximately -50 mV and then stepping to approximately -90 mV for increasing periods of time (0.5-5.0 s) before delivering a test pulse. The amplitude of the test pulse response decreased as a function of the hyperpolarizing step duration. When the test pulse response amplitudes were plotted against the hyperpolarizing step duration, the points reflected an exponential decay with an average time constant of 2.05 +/- 1.38 (SD) s.(ABSTRACT TRUNCATED AT 400 WORDS)

Differentiation of Na(+)-K+ pumps of low-K+ sheep red blood cells is promoted by Lp membrane antigens

Na(+)-K+ pumps of red blood cells from sheep of the low-K+ (LK) phenotype undergo differentiation during circulation, manifested in part by a striking increase in sensitivity to inhibition by intracellular K+ (Ki). Pumps of red blood cells from sheep from the allelic phenotype, high K+ (HK), do not undergo this type of maturation. The hypothesis was tested that the Lp antigen, found on LK but not HK cells, is responsible for the maturation of LK pumps. Lp antigens have been shown to inhibit LK pumps because anti-Lp antibody stimulates the pumps by relieving inhibition by the antigen. Lp antigens were recently shown to be molecular entities separate from Na(+)-K+ pumps [Xu, Z.-C., P. Dunham, J. Munzer, J. Silvius, and R. Blostein. Am. J. Physiol. 263 (Cell Physiol. 32): C1007-C1014, 1992]. The test of the hypothesis was to modify the Lp antigens of immature LK red blood cells with two kinds of treatments, anti-Lp antibody and trypsinization (which cleaves Lp), and to observe the effects of these treatments on maturation of pumps during culture of the cells in vitro. Both of these treatments prevented the maturation of the kinetics of the pumps to the Ki-sensitive pattern, supporting the hypothesis that interaction of the pumps with Lp antigens is responsible for the maturation of the pumps. Strong supportive evidence came from experiments on Na(+)-K+ pumps from rat kidney delivered into immature LK sheep red blood cells by microsome fusion.(ABSTRACT TRUNCATED AT 250 WORDS)

[An experimental study on the mechanism of antiatherosclerotic effect of nifedipine]

Thirty male N-Z white rabbits were randomized into 3 groups (10 each). Normal control group (C) were fed regular chow. Atherosclerotic control group (CAS) were fed a chow containing 1% cholesterol. Nifedipine group (N) were fed 1% cholesterol chow and nifedipine 40 mg/animal/day. The experiment lasted for 12 weeks. Blood total cholesterol, HDL-C, MDA, 6-keto-PGF1 alpha and TXB2 were measured. After the sacrifice of the animals, electron probe microanalysis was employed to cryo-ultrathin sections of the aorta for measuring cytoplasmic calcium content in situ in the medial smooth muscle cells. The area of atherosclerotic plaques of the aortae was planimetried with computer. The results showed that MDA and TXB2 in group CAS were markedly higher than those in groups C and N (P < 0.01 or 0.05). The cytoplasmic calcium in group CAS was significantly higher than that in groups C and N (P < 0.01). The difference between groups C and N was not significant. The area of atherosclerotic lesions in group CAS was 44 +/- 8%, markedly larger than that in group N (13 +/- 5%, P < 0.01). The antiatherosclerotic effects of nifedipine may be mainly by a mechanism of inhibiting intracellular calcium overload.

Evidence for an effect of phospholamban on the regulatory role of ATP in calcium uptake by the calcium pump of the cardiac sarcoplasmic reticulum

The purpose of this study was to investigate the functional relationship between phospholamban and the nucleotide site of the calcium pump protein of the cardiac sarcoplasmic reticulum. We used control and trypsin-treated cardiac microsomes in which cleavage of the inhibitory cytoplasmic domain of phospholamban is associated with an activation of the calcium pump similar to that produced by protein kinase A catalyzed phospholamban phosphorylation. Phenylglyoxal was shown to inactivate the calcium pump in a pseudo-first-order reaction by binding to a single Arg at the nucleotide binding site. No differences upon trypsin treatment of microsomes were observed in the kinetics of phenylglyoxal inactivation or the ability of millimolar ATP to protect against inactivation. In subsequent kinetic studies, Ca-uptake rates measured at saturating Ca2+ and 5 microM-1 mM MgATP2- were increased 15-32% by trypsin treatment in each of three different microsome preparations. Double-reciprocal plots of the data showed marked downward curvature indicating an acceleratory effect associated with ligand binding to a lower affinity site. At 0.32 microM Ca2+, Ca-uptake rates were lower than at 11 microM Ca2+ but were stimulated to a greater extent by trypsin treatment; control microsomes showed reduced evidence of apparent negative cooperativity. At 0-2 microM MgATP2- and saturating Ca2+, there was a 50% increase in Vmax(app) when the Hill coefficient (N) was 1. At 0-10 microM MgATP2-, second-site binding was evident. At both 0-10 microM and 5 microM-1 mM MgATP2-, trypsin-treated microsomes showed greater activation of Ca uptake attributable to second-site binding than did control microsomes.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of injection Salvia miltiorrhizae on peritoneal dialysis]

Effective volume of blood flow of peritoneal capillary is an important factor influencing the efficiency of peritoneal dialysis. Injection of Salvia miltiorrhizae (ISM) could dilate the blood vessels and improve microcirculation. The effect of peritoneal dialysis with three kinds of dialytic fluid was studied. The dialysate of first group contained ISM, the second used dialysate only, the third contained dopamine. The result found that ISM could markedly increase the clearance rate and ultrafiltration rate of the peritoneum to creatinine, urea nitrogen and uric acid. Three concentrations of ISM (4%, 6%, 8%) were also compared. This comparison showed that 6% injection of ISM was the optimal concentration.

Rat kidney Na-K pumps incorporated into low-K+ sheep red blood cell membranes are stimulated by anti-Lp antibody

A genetic dimorphism of sheep red blood cells characterized by differences in the intracellular K+ concentration of mature red blood cells (low-K+ or high-K+ cells) reflects differences in their Na-K pumps and is known to be linked to the ML blood group system. We investigated the relationship of Na-K pumps in red blood cells from sheep of the low-K+ phenotype with an antigen, Lp, that is restricted to low-K+ cells. Anti-Lp antibody stimulates the Na-K pumps in these cells presumably by relieving inhibition of the pumps by Lp. The questions addressed were as follows: is Lp a molecular entity distinct from pumps and, if so, can it interact with pumps of exogenous origin? Rat kidney Na-K pumps were incorporated by fusion of microsomes into either low-K+ or high-K+ sheep red blood cells. The activity of the exogenous kidney pumps was distinguished from that of the endogenous red blood cell pumps by the low sensitivity of rodent pumps to ouabain. Anti-Lp stimulated by > 50% rat kidney pumps incorporated into immature low-K+ sheep cells. This indicates that Lp is a distinct molecular entity free to dissociate from endogenous pumps and inhibit exogenous pumps. Anti-Lp did not stimulate kidney pumps incorporated into mature low-K+ cells but did stimulate kidney pumps following in vitro maturation of microsome fused reticulocytes, probably reflecting restriction of lateral movement of pumps and antigens by the cytoskeleton in mature cells.

Kinetics of aluminum in rats. IV: Blood and cerebrospinal fluid kinetics

Aluminum causes central nervous system (CNS) toxicities in both humans and various animal species. Although blood aluminum concentrations are monitored in the clinic, very little is known regarding the relationship between such concentrations and corresponding CNS aluminum content. As a first step in that direction, this study was undertaken to simultaneously determine blood and CSF kinetics of this element. Following intravenous injection of aluminum (1 mg/kg), there was a rapid (within 30 min, post injection) increase in CSF aluminum; peak concentrations (38-45 ng/ml) were achieved between 2-3 h. While peak blood aluminum concentrations increased about 58-fold from the pre-dose value (from 256 +/- 120 to 14,730 +/- 388 ng/ml), corresponding increases in CSF aluminum were only about 20-fold. Blood and CSF aluminum concentrations declined monoexponentially with half-lives of 2.77 and 3.45 h, respectively (P < 0.05). Results from these showed that blood and CSF compartments achieve equilibrium and indicated the feasibility of determining brain aluminum content using blood concentrations.

Aluminum-induced acute cholinergic neurotoxicity in rat

In the present study the acute effect of intravenous aluminum chloride (1 mg/kg) on choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities of rats was investigated. Aluminum was found to cross the blood-brain barrier (BBB) as indicated by the detection of aluminum in the cerebrospinal fluid (CSF) 30 min after femoral vein injection. Two hours following aluminum injection, ChAT activity in the basal forebrain and hippocampus was significantly reduced by 30% and 22%, respectively, whereas no change was observed in the caudate nuclei. On the other hand, AChE activity was significantly increased by 45% in the caudate nuclei, whereas little change was observed in other brain areas. This report demonstrates that rapid transport of Al across the BBB, and the acute nature of Al neurotoxicity in rats.

Grafted neostriatal neurons express a late-developing transient potassium current

Previous anatomical and physiological studies of neostriatal grafts have suggested that transplanted neurons do not develop beyond an early postnatal stage. We have tested whether this hypothesis can be generalized by characterizing the developmentally regulated Ca-independent potassium currents in graft neurons. These currents were studied using a combination of the whole-cell voltage-clamp technique with acutely-dissociated neurons and intracellular recording in slices. In all of the graft neurons examined with voltage-clamp techniques (n = 13), evidence was found for a slowly-inactivating potassium current that is seen only beyond the third or fourth postnatal week in normal rats. A current resembling the delayed rectifier was also seen in all sample neurons. The rapidly inactivating A-current which dominates recordings from nearly all immature neurons was seen in only about half (54%, 7/13) of the graft neurons; in a sample of normal adult striatal neurons, the A-current was detected in a similar percentage of neurons (41%, 25/62). Recordings of graft neurons in slices corroborated the voltage-clamp findings in revealing a slowly inactivating outward current that acts in the subthreshold potential range. These findings suggest that graft neurons express the normal complement of depolarization-activated potassium channel proteins seen in adult neurons.

Morphology of intracellularly stained spiny neurons in rat striatal grafts

Two to six months after implantation of fetal striatal primordia into the kainic acid-lesioned neostriatum of adult rats, spiny neurons in the grafts were stained intracellularly with biocytin. To determine whether the spiny neurons in the grafts differentiate morphologically as in the host neostriatum, the intracellularly stained spiny neurons in the grafts were studied with light and electron microscopy and compared with that of spiny neurons in the host neostriatum. The spiny neurons in the grafts had ovoid or polygonal cell bodies with dendrites radiating in all directions. The somata were smooth and the dendrites, except for their most proximal portions, were rich in spines. All these features resembled the appearance of spiny neurons in the intact neostriatum. However, quantitative studies showed that the somata of spiny neurons in the grafts were larger than those in the host neostriatum (projected cross-sectional areas of 230 +/- 64.6 microns 2 in the grafts and 158 +/- 28.9 microns 2 in the host) and the spine density of graft neurons was lower than that of host neurons. Cells near the border of the grafts had dendrites extending both into the graft and into the host neostriatum. In these cells, the dendrites in the grafts had fewer spines than the dendrites in the host tissue. The axons of spiny neurons in the grafts had very large and dense intrastriatal collateral arborizations, which occupied a much larger volume than that of the dendritic domain of the parent cells. The local axonal arborizations of each of these cells filled almost the entire graft. In some cells, axonal branches were traced outside the grafts and were seen to enter the internal capsule fascicles. Unlike spiny neurons in the normal adult neostriatum, the spiny cells of the graft could have nuclear indentations. With this exception, the ultrastructural features of spiny neurons in the grafts were very similar to those in the hosts. Many unlabeled boutons made synapses on identified spiny neurons in the grafts. Terminals with small round vesicles made synaptic contacts on dendritic shafts and dendritic spines, while terminals with flattened or pleomorphic vesicles contacted somata, dendrites, and dendritic spines. Labeled axon collaterals of graft neurons made symmetrical synapses on somata, dendrites and spines in the grafts and in the host neostriatum. In the grafts, more than 60% of the axon terminals contacted dendritic shafts. The proportion of axosomatic and axospinous synapses varied substantially from cell to cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative amino acid sequence analysis of VP4 for VP7 serotype 6 bovine rotavirus strains NCDV, B641, and UK

In a previous study (S. Zheng, G. N. Woode, D. R. Melendy, and R. F. Ramig, J. Clin. Microbiol. 27:1939-1945, 1989), it was predicted that the VP7 serotype 6 bovine rotavirus strains NCDV and B641 do not share antigenically similar VP4s. In this study, gene 4 and the VP7 gene of B641 were sequenced, and the amino acid sequences were deduced and compared with those of NCDV and bovine rotavirus strain UK. Amino acid sequence homology in VP7 between the three strains was greater than 94%, confirming their relationship as VP7 serotype 6 viruses. VP4 of B641 showed amino acid homology to UK of 94% but only 73% homology to NCDV. Sequence comparison of a variable region of VP8 demonstrated amino acid homology of 53% between B641 and NCDV, whereas B641 and UK were 89% homologous in this region. These results confirm the earlier prediction that although the same serotype by VP7 reactivity, B641 and NCDV represent different VP4 serotypes. This difference in VP4 may have contributed to the lack of homotypic protection observed in calves, implicating VP4 as an important antigen in the active immune response to rotavirus infection in bovines.

CD2 rocking modes as quantitative infrared probes of one-, two-, and three-bond conformational disorder in dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylcholine/cholesterol mixtures

The use of CD2 rocking modes in the IR spectrum as quantitative probes of phospholipid conformational disorder has recently been described for aqueous dispersions of 1,2-dipalmitoylphosphatidylcholine (DPPC) and DPPC/cholesterol mixtures [Mendelsohn et al. (1989) Biochemistry 28, 8934-8939; Davies et al. (1990) Biochemistry 29, 4368-4373]. Initial studies focused at the 4, 6, and 10 acyl chain positions of DPPC. In the current work, the method is extended to the 2, 3, 12, and 13 positions. Conformational disorder in the L alpha phase is approximately the same (about 20% gauche) at positions 4, 10, and 13, but an unexpected higher value is observed (about 30%) at the 6 position. Cholesterol (33 mol%) restricts gauche rotamer formation by factors ranging from 6 to 9 at positions 4 and 6, respectively, to 1.5-2 at positions 10, 12, and 13. Quantitative analysis for the DPPC/cholesterol "liquid-ordered" phase indicates the occurrence of 1.2 gauche bonds/chain, a marked reduction from the 3.6-4.2 gauche bonds/chain for DPPC alone. Proximity to the ester moiety at acyl chain position 3 perturbs the vibrational coupling patterns of the CD2 rocking modes and eliminates their sensitivity to conformational change. In addition, the feasibility of a method based on the conformation-dependent coupling between CD2 rocking frequencies of two successive CD2 groups for the quantitative detection of specific, position-dependent king (gtg') and isolated gauche (gtt) conformers is demonstrated. Finally, comparisons between IR measurements and explicit theoretical predictions of acyl chain conformational order are presented.

Analysis of serotypes and electropherotypes of equine rotaviruses isolated in the United States

Equine group A rotaviruses isolated over a 10-year period in New York State, New Jersey, Kentucky, and Texas were compared serotypically and electropherotypically. All isolates were determined to be serotype 3 by reaction with hyperimmune antiserum to the serotype 3 H-2 strain of equine rotavirus. All displayed RNA electrophoretic migration patterns related to that of the H-2 strain but distinct from that of serotype 5 strain H-1. A serologic survey of 184 mares in Kentucky, which was done to determine the incidence of H-1 and H-2 infections, showed geometric mean serum neutralizing titers to the H-2 strain of equine rotavirus to be significantly higher than those to the H-1 strain. These data suggest that the serotype 3 H-2 strain is the dominant equine rotavirus in Kentucky and perhaps elsewhere in the United States. We were unable to produce confirmational evidence that the H-1 strain occurs as a natural infection in the United States.

Synaptic potentials evoked in spiny neurons in rat neostriatal grafts by cortical and thalamic stimulation

1. Fetal rat striatal primordia were implanted into the neostriatum of adult rats 2 days after kainic acid lesion. Two to 6 mo after transplantation, in vivo intracellular recording and staining were performed to study the responses of spiny neurons in the grafts to the cortical and thalamic stimuli. The physiological characteristics and synaptic responses of 27 cells recorded in the grafts were compared with a sample of 23 neurons recorded from the surrounding host neostriatum in the same animals. Nineteen of the graft neurons and 19 of the host neurons were identified as spiny neurons by intracellular staining with biocytin. The responses of the remaining neurons were the same as those of identified spiny cells. 2. The spontaneous synaptically driven membrane potential shifts and long-lasting responses to afferent stimulation that are characteristic of neostriatal cells in normal animals were greatly reduced or absent in graft neurons. Presumably this reflects the reduction in synaptic input to the grafts and the lack of convergence of inputs from diverse sources. 3. Short-latency synaptic responses to cortical and thalamic stimulation were present and could consist of either excitatory postsynaptic potentials (EPSPs) or inhibitory postsynaptic potentials (IPSPs). The IPSPs were accompanied by a membrane conductance increase, and their reversal potentials could be altered by injection of chloride ions. Several minutes after impaling the cell, the IPSPs gradually disappeared, and the same stimuli could then evoke EPSPs. The disappearance of the IPSPs was independent of the presence of chloride in the electrodes. Most of the EPSP responses appeared to be monosynaptic but occurred at longer latencies than those seen in host neurons of the same type. 4. In cells not exhibiting IPSPs, or after the IPSP responses disappeared, cortical or thalamic stimulation could evoke slow depolarizing potentials and bursts of action potentials. These could not be evoked by current injection. They could be prevented or delayed by an exaggerated action potential after hyperpolarization that developed in neurons maintained in a depolarized state for several seconds, but could not be prevented by passage of hyperpolarizing current from the recording electrode. 5. The input resistance of graft spiny neurons was higher than that of the host cells, and time constants were longer. Both of these properties appeared to be due to the absence of the strong inward rectification that is usually present at resting membrane potentials in neostriatal neurons.

Restoration of thalamostriatal projections in rat neostriatal grafts: an electron microscopic analysis

The thalamostriatal projections to rat neostriatal grafts were studied by using the Phaseolus vulgaris-leucoagglutinin (PHA-L) axonal tracing technique. Two to 6 months after implantation of striatal primordia into adult neostriata, PHA-L was injected into two different portions of the intralaminar nuclear complex of the thalamus. In the host neostriatum, labeled fibers from the parafascicular nucleus (PF) arborized in a large region in the neostriatum, but avoided small patchlike areas. Most of the fibers from PF had irregular curved trajectories with short side branches that formed boutons. Labeled fibers from the centromedial and paracentral nuclei (CeM-PC) projected to a similarly large area within the neostriatum but did not show any nonuniformity. CeM-PC axons had relatively straight trajectories and formed boutons en passant. Both sets of thalamostriatal projection fibers were found in the grafts. Some of the labeled fibers in the grafts formed dense, focal arborizations. Compared to the host neostriatum, the distribution of postsynaptic elements in the grafts was altered dramatically. In the host neostriatum, 89% of the terminals from PF terminated onto dendritic shafts; 93% of the CeM-PC terminals contacted dendritic spines. However, only 47% of the PF terminals in the grafts contacted dendritic shafts; 53% of them terminated on dendritic spines. In grafts, 81% of the terminals from CeM-PC region contacted dendritic spines; 19% of them made synapses on dendritic shafts. The shift of postsynaptic elements in the grafts suggests a loss of pathway specificity in the induction of dendritic spines on neostriatal neurons in grafts.

[Value of gastroscopy in postoperative patients with gastric cancer]

From September 1980 to May 1987, fiberoptic gastroscopy was performed in 3538 patients. Of them, 356 (10%) had received operation for gastric cancer. A second primary cancer was found in 31 cases, recurrent gastric cancer in 18 and adenoma in 87. Among the 138 asymptomatic operated patients, a second primary cancer developed in 8, and 6 of them were in the early stage. In the 218 symptomatic operated patients, a second primary cancer developed in 23, and 10 of them were in the early stage. The results suggest that gastroscopic examinations at regular intervals are mandatory for asymptomatic postoperative patients.

Modulation by polyelectrolytes of canine cardiac microsomal calcium uptake and the possible relationship to phospholamban

Calcium uptake and (Ca2+ + Mg2+)-ATPase activity in canine cardiac microsomes were found to be stimulated by heparin and various other polyanions. Prior treatment of the microsomes with the ionophores alamethicin or A23187 produced no change in the extent of stimulation of the ATPase activity by heparin yet eliminated net calcium uptake. This finding and a lack of change in the stoichiometric ratio of mol of calcium transported/mol of ATP hydrolyzed (calcium:ATP) suggest that the effect of heparin is on the calcium pump rather than on a parallel calcium efflux pathway. Certain polycationic compounds including poly-L-arginine and histone inhibited both cardiac and fast skeletal muscle microsomal calcium uptake and also produced no change in the stoichiometric ratio of calcium to ATP. Several lines of evidence indicate that the polyanionic compounds tested stimulate calcium uptake by interacting with phospholamban, the putative phosphorylatable regulator of the cardiac sarcoplasmic reticulum calcium pump, whereas polycationic compounds appear to interact with the pump. (i) Heparin stimulated calcium uptake to the same extent as protein kinase A or trypsin, whereas prior phosphorylation or tryptic cleavage of phospholamban from the membrane abolished the stimulatory effect of heparin. (ii) Calcium uptake and (Ca2+ + Mg2+)-ATPase activity in fast skeletal muscle microsomes, which lack phospholamban, were unaffected by heparin. (iii) Purified cardiac (Ca2+ + Mg2+)-ATPase activity was no longer stimulated by heparin yet was still inhibited by polycationic compounds. The heparin-induced stimulation of calcium uptake was dependent on the pH and ionic strength of the heparin-containing preincubation medium, hence electrostatic interactions appear to play a significant role in heparin's stimulatory action. The data are consistent with an inhibitory role of the positively charged cytoplasmic domain of phospholamban with respect to calcium pump activity and the relief of the inhibition upon reduction in phospholamban's positive charge by phosphorylation or binding of polyanions.

Polyphosphoinositide formation in isolated cardiac plasma membranes

Phosphatidylinositol (PtdIns) and phosphatidylinositol 4-phosphate (PtdIns4P) kinase activities in plasma membranes isolated from canine left ventricle were partially characterized, and their sensitivity to a number of intracellular variables was established. PtdIns and PtdIns4P kinase activities were estimated by the formation of [32P]PtdIns4P and [32P]phosphatidylinositol 4,5-bisphosphate ([32P]PtdIns(4,5)P2), respectively, when membranes were incubated with [gamma-32P]ATP and 0.1% Triton X-100. Unlike [32P]PtdIns4P formation [32P]PtdIns(4,5)P2 formation required exogenous (PtdIns4P) substrate. [32P]PtdIns4P and [32P]PtdIns(4,5)P2 formation were insensitive to Ca2+ at concentrations ranging from 0.1-30 microM. The hydrolysis of [32P]PtdIns4P was less than 15% under standard assay conditions for measuring its formation, and was unaffected by any of the variables tested. The apparent Km of the PtdIns kinase for ATP was 53 +/- 13 (S.E.M.) microM (N = 3). ADP inhibited [32P]PtdIns4P formation competitively with respect to ATP, the Ki being 0.4 mM. The data indicate that ADP is a poor competitive inhibitor of PtdIns kinase at the concentrations which are believed to be present intracellularly normally or which may be attained during mild hypoxia provided ATP levels are maintained in the millimolar range. Hence, any response of the myocardium to alpha-adrenergic hormones during mild hypoxia would be largely unimpaired by effects of Ca2+ on PtdIns and PtdIns(4,5)P2, or of ADP on PtdIns kinase activity.

[Surgical treatment of carcinoma of gastric cardia in aged patients--analysis of 101 cases]

101 aged patients with cardiac carcinoma resected by upper midline abdominal approach and left costal cartilage amputation were reported. The merits of the operation were: better exposure; good tolerance of patients with embarrassed heart and lung functions; un-influenced functions of the diaphragm and intrathoracic vital organs because neither the diaphragm was incised nor the thorax was opened and blood loss was less than 200 ml during the operation. The authors believe that this method is suitable for the aged patients and patients with deficient cardiopulmonary functions. Long-term follow up results are needed for critical evaluation.

Restoration of the corticostriatal projection in rat neostriatal grafts: electron microscopic analysis

The corticostriatal projection in rat neostriatal grafts was studied by using the axonal transport of Phaseolus vulgaris-leucoagglutinin. The neostriatal primodia from 15-18-day embryos were used to make a cell suspension which was implanted unilaterally into the rat neostriatum 3-5 days after kainic acid lesion. Two to four months later, regions of the frontal cortex ipsilateral to the grafts were injected iontophoretically with Phaseolus vulgaris-leucoagglutinin. There were many Phaseolus vulgaris-leucoagglutinin labeled cortical fibers in the host neostriatum. Although the density of labeled fibers in the grafts was much lower than that in the surrounding host tissue, some fibers could be seen to enter the grafts and form terminal arborizations. The morphology of labeled fibers in the graft differed from that of corticostriatal fibers from the same injection but distributing in the host neostriatum. The labeled fibers in the host neostriatum arborized in an extended pattern, branching infrequently and making most of their synapses en passant at varicosities along their courses. The labeled fibers in the grafts made more dense arborizations with many short branches that formed clusters of terminals confined to small foci along their courses. The cellular composition and the structure of the neuropil in the neostriatal grafts were similar to that of the neostriatum. As those in the host, labeled corticostriatal terminals in the grafts contained densely packed round vesicles and made asymmetric synapses on dendritic spines, dendritic shafts and somata. A quantitative analysis, however, revealed that the distribution of postsynaptic elements of labeled boutons in the grafts was different from that in the hosts. More than 90% of the labeled cortical terminals in the host neostriatum contacted dendritic spines whereas only 47% of the labeled terminals in the grafts contacted spines, and 50% of them terminated on the dendritic shafts. The present study provides direct anatomic evidence to demonstrate the restoration of the corticostriatal projection in grafts. The difference in the distribution of postsynaptic elements in the grafts and the hosts may represent a response to the decreased innervation density of cortical inputs to the graft tissue, and may contribute to the recovery of corticostriatal responses by increasing the effectiveness of transmission by the fibers that do grow into the graft and form contacts there.

Differences in calcium uptake in native canine cardiac microsomes are correlated with the ratio of unphosphorylated to phosphorylated phospholamban as determined by Western blot analysis

Phospholamban (PLM) is detectable by Western blot analysis of canine cardiac microsomes using rabbit antiserum against a peptide containing the 2 to 30 amino acid sequence of PLM. Phosphorylated PLM is distinguishable from the unphosphorylated form by virtue of a reduced electrophoretic mobility. Utilizing digital image analysis to determine relative band densities, it was found that the ratio of unphosphorylated to phosphorylated PLM is correlated with the rate of calcium uptake in 5 preparations of native microsomes (r = 0.94, p less than 0.01). The present analysis may be useful for determining the phosphorylation state of PLM in microsomes obtained from animals in physiological states characterized by impaired sarcoplasmic reticulum calcium pump activity.

Localization of hydrophobic ions in phospholipid bilayers using 1H nuclear Overhauser effect spectroscopy

The binding location for the hydrophobic ions tetraphenylphosphonium (TPP+) and tetraphenylboron (TPB-) was studied in sonicated phosphatidylcholine (PC) vesicles by measuring time-dependent and steady-state intermolecular 1H nuclear Overhauser effects (NOE's). Intermolecular cross-relaxation was also investigated by two-dimensional NOE spectroscopy. Information on the distance and order parameter dependence of the NOE's was obtained from a simple simulation of the NOE's in the alkyl chain region. Taken together, the NOE data and the simulation provide strong evidence that TPB- and TPP+, at low concentrations (less than or equal to 10 mol%), are localized in the alkyl chain region of the bilayer. At these lower concentrations of TPP+ or TPB-, no significant effect on lipid 13C T1 or T2 relaxation rates is detected. The proposed location is consistent with the expected free energy profiles for hydrophobic ions and with the carbonyl oxygens or interfacial water as the source of the membrane dipole potential. At higher ion/lipid ratios (greater than or equal to 20 mol%), TPB-/lipid NOE's increase. This results from a specific association of TPB- with the choline head group.

Phospholipid packing and conformation in small vesicles revealed by two-dimensional 1H nuclear magnetic resonance cross-relaxation spectroscopy

Two-dimensional 1H-NMR spectroscopy has been used to examine cross-relaxation in sonicated phospholipid vesicle systems. The observed pattern of proton cross-relaxation reveals several important features of these vesicle systems. For example, cross-relaxation rates on each monolayer of the vesicle system can be resolved and reflect the expected geometric packing constraints of the vesicle system. Small but significant magnetization-exchange is also seen to develop between the headgroup N-methyl resonance and the terminal methyl resonance. Spectra taken with deuterated lipids indicate that this exchange is not mediated by spin-diffusion down the length of the alkyl chains. Since spin-diffusion is the only process that is expected to facilitate magnetization-exchange over distances of 15-20 A, a close proximity of headgroup and terminal methyl protons in a fraction of the membrane lipid is indicated by these results. This could occur by events such as lipid interdigitation or alkyl chain bends that terminate lipid alkyl chain ends near the membrane surface.