Group II intron mobility occurs by target DNA-primed reverse transcription

Mobile group II introns encode reverse transcriptases and insert site specifically into intronless alleles (homing). Here, in vitro experiments show that homing of the yeast mtDNA group II intron aI2 occurs by reverse transcription at a double-strand break in the recipient DNA. A site-specific endonuclease cleaves the antisense strand of recipient DNA at position +10 of exon 3 and the sense strand at the intron insertion site. Reverse transcription of aI2-containing pre-mRNA is primed by the antisense strand cleaved in exon 3 and results in cotransfer of the intron and flanking exon sequences. Remarkably, the DNA endonuclease that initiates homing requires both the aI2 reverse transcriptase protein and aI2 RNA. Parallels in their reverse transcription mechanisms raise the possibility that mobile group II introns were ancestors of nuclear non-long terminal repeat retrotransposons and telomerases.

Action of alpha-amanitin during pyrophosphorolysis and elongation by RNA polymerase II

Using defined elongation complexes formed on dC-tailed templates with Drosophila RNA polymerase II, we have examined elongation, pyrophosphorolysis, and DmS-II-mediated transcript cleavage and the inhibitory effect of alpha-amanitin on these processes. Analysis of pyrophosphorolysis on soluble or immobilized and templates confirmed that NTPs are liberated instead of dinucleotides that are released during DmS-II-mediated transcript cleavage. 10 microgram/ml alpha-amanitin completely inhibited DmS-II-mediated transcript cleavage but allowed extended pyrophosphorolysis and nucleotide addition to occur. alpha-Amanitin dramatically decreased the Vmax for nucleotide addition but only slightly affected the Km for nucleotides. Although the processes ae mechanistically distinct, both pyrophosphorolysis and DmS-II-mediated transcript cleavage frequently resulted in similar patterns of shortened transcript. Since polymerase molecules encounter similar kinetic barriers during both processes, it is possible that there is a common step in the reverse movement of the polymerase.

Cocaine increases extraneuronal levels of aspartate and glutamate in the nucleus accumbens

Intracerebral microdialysis was used to assess the effects of cocaine-HCl on extracellular concentrations of the excitatory amino acids aspartate and glutamate in the nucleus accumbens of awake, freely moving rats. After an initial equilibration period, cocaine (7.5, 15 or 30 mg/kg) or saline was injected i.p., and samples were collected for an additional 2 h. The highest dose of cocaine (30 mg/kg, i.p.) caused a 4-fold increase in glutamate levels and an 18-fold increase in aspartate levels over baseline. To verify that the source of the extracellular aspartate and glutamate was neuronal, additional experiments were conducted using Ca(2+)-free microdialysis buffer, and buffer containing 10 microM tetrodotoxin. Local perfusion with Ca(2+)-free buffer reduced the increase of extracellular aspartate and glutamate in rats injected with 30 mg/kg cocaine. Tetrodotoxin significantly decreased the cocaine-induced increase in excitatory amino acids, but not the behavioral response.

[A new and simple method of evaluating left ventricular contractility and its application]

After making theoretical analysis, we detected the relationship among the maximal tension of ventricular contraction, left ventricular end-systolic pressure and stroke volume, and then derived a new and simple method of evaluating left ventricular contractility, the slope of the left ventricular end-systolic pressure-volume relation (Emax). Twelve mongrel male dogs were used to test this method. The results show that the value of Emax (0.60 +/- 0.16 kPa/ml) coming from this simple method is very close to that from complicated method; this method has good repetitiveness and is very sensitive to the variation of myocardial contraction. Using the method for evaluating left ventricular contraction after ischemia, we found the Emax more cogent than other hemodynamic parameters. Therefore, this method is an efficient method of evaluating left ventricular contraction.

An extensive subfrontal approach to the lesions involving the skull base

A modification of the transbasal approach of Dorome called extensive subfrontal approach and the surgical results with this approach in 22 cases are presented. Bilateral frontal craniotomies incorporated with the removal of orbital ridges and part of the orbital roofs were fashioned en bloc. It may give rise to good exposure of the midline lesions of the anterior, middle and posterior skull base, minimizing the need for the retraction of frontal lobes. There was no surgical mortality in this series of cases. Of the 20 cases with tumors, total resections were achieved in 11 cases, subtotal or large resections in 4 cases and partial resection in one case. Two patients with spontaneous rhinorrhea were successively treated surgically. 21 patients had a follow-up with a time ranging from 1-11 years (a mean of 3 years). 15 patients resumed their jobs with no evidence of recurrence of the original disease, and 5 patients able to live self-care. One patient with an olfactory neuroblastoma died 3 years after the operation owing to relapse of the tumor.

[Clinical significance of fibrinolytic system defectiveness in exercise induced myocardial ischemia and its mechanism]

Plasma levels of tissue type plasminogen activator (tPA), plasminogen activator inhibitor (PAI), fibrinogen (Fg), thromboxane B2 (TXB2), 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), renin activity (PRA) and angiotensin II (ANGII) were assayed in 18 patients with coronary heart disease and 11 healthy subjects before and after submaximal treadmill exercise test according to "Bruce programme". All patients showed significant (> or = 50%) stenosis of at least one branch of the coronary arteries in coronary angiography and normal levels of serum trinitroglycerin. Drugs of dipyridamole, heparin, warfarin and aspirin were not administered to the patients two weeks before the test. The results were as follows: (1) Plasma PAI activity and Fg levels in 12 patients with positive test were remarkablly higher than in the remaining 6 subjects with negative test in the CHD group and in the control before and after exercise. Plasma tPA antigen changed in a reverse way. (2) Plasma levels of TXB2, PRA and ANGII in the positive test subgroup of CHD were higher than in the negative test subgroup and in the control after exercise, but differences of the parameters among the three groups were insignificant before exercise. The study suggests that defectiveness of fibrinolytic system in CHD patients was shown mainly as disorder of tPA-PAI equilibrium and that decreased fibrinolytic activity and increased PAI in exercise-induced myocardial ischemia have relations with activation of platelets and renin-angiotensin system.

Human tumors are methionine dependent in vivo

Methionine-dependence is a tumor-specific biochemical defect expressed by the inability or decreased ability of tumors to grow under the condition of methionine-depletion. Many reports have shown that methionine-dependence occurs in human tumors of all types, including fresh surgical specimens in vitro. However, in vivo determinations of methionine-dependence have thus far been made only in rodent malignant tumors using methionine-deficient diets. We report here for the first time that human cancer xenografts in nude mice are methionine-dependent and when fed a methionine-free diet tumor growth is greatly inhibited. The body weight of mice on the methionine-free diet was found to be maintainable by once-per-week administration of methionine. The data presented here suggest that methionine-dependence can be an important target for human cancer treatment.

[The posterolateral suboccipital approach to the lesions located at the anterior portion of the craniocervical junction]

A surgical approach to the anterior lower brainstem and upper cervical spinal cord consists of a fashion of unilateral suboccipital scalp flap, exposure and resection of the suboccipital bone and hemilamina of C1, removal of occipital condyle and the lateral mass of C1 (occasionally). The satisfaction of exposing the anterolateral portion of lower brainstem and upper cervical spinal cord can be obtained with minimal retraction of the nervous tissue. 13 patients, 9 with tumors, 2 with giant vertebral aneurysms, 2 with craniocervical malformations, underwent this operative procedure with no surgical mortality and morbidity which related to the approach.

Endolymphatic stromal myosis of the uterus. Clinicopathological analysis of five cases

Five cases of endolymphatic stromal myosis (ELSM) were studied using histological, histochemical and immunohistochemical methods. ELSM is a well-differentiated tumor resembling the normal endometrial stoma, with a low mitotic activity. So ELSM is considered as a kind of potentially malignant tumor different from endometrial stomal sarcoma and benign stromal nodules as well, though it can metastasize to the outside of uterus. ELSM may be derived from the stem cells that are normally present in the stroma of uterus, and can manifest multidifferentiation.

[Human lens epithelial cell culture and its proliferative inhibition in vitro]

The cultures of human lens epithelial cells taken from both normal and cataractous lenses were established in vitro. The biological characteristics and the histological changes of the cells were investigated. 5-Fluorouracil (5-Fu), Homoharring tonine (HH) and Harmeline (H) were used for the inhibition of the proliferative cells in the experiment. The results revealed that the in vitro survival capacity of the human lens epithelial cells is limited and the proliferative capacity of the cells is negatively correlated to the donor age. HH and H can effectively inhibit the lens epithelial cell proliferation. Based on the results of this report, performing small and smoothly edged anterior capsulorhexis in extracapsular cataract extraction may possibly decrease the incidence of the post-operative opacification of the posterior capsule.

Purification and characterization of two potent heat-stable protein inhibitors of protein phosphatase 2A from bovine kidney

Two heat-stable protein inhibitors of protein phosphatase 2A (PP2A), tentatively designated I1PP2A and I2PP2A, have been purified to apparent homogeneity from extracts of bovine kidney. The purified preparations of I1PP2A exhibited an apparent M(r) approximately 30,000 and 250,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel permeation chromatography on Sephacryl S-300, respectively. In contrast, the purified preparations of I2PP2A exhibited an apparent M(r) approximately 20,000 and 80,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel permeation chromatography on Sephacryl S-200, respectively. The purified preparations of I1PP2A and I2PP2A inhibited PP2A with 32P-labeled myelin basic protein, 32P-labeled histone H1, 32P-labeled pyruvate dehydrogenase complex, 32P-labeled phosphorylase, and protamine kinase as substrates. By contrast, I1PP2A and I2PP2A exhibited little effect, if any, on the activity of PP2A with 32P-labeled casein, and did not prevent the autodephosphorylation of PP2A in incubations with the autophosphorylation-activated protein kinase [Guo, H., & Damuni, Z. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 2500-2504]. The purified preparations of I1PP2A and I2PP2A had little effect, if any, on the activities of protein phosphatase 1, protein phosphatase 2B, protein phosphatase 2C, and pyruvate dehydrogenase phosphatase. With 32P-labeled MBP as a substrate, kinetic analysis according to Henderson showed that I1PP2A and I2PP2A were noncompetitive and displayed a Ki of about 30 and 25 nM, respectively. Following cleavage with Staphylococcus aureus V8 protease, I1PP2A and I2PP2A displayed distinct peptide patterns, indicating that these inhibitor proteins are the products of distinct genes. The N-terminal amino acid sequences of the purified preparations indicate that I1PP2A and I2PP2A are novel proteins.

The human tumor cell-derived collagenase stimulatory factor (renamed EMMPRIN) is a member of the immunoglobulin superfamily

Tumor cell-derived collagenase stimulatory factor, renamed extracellular matrix metalloproteinase inducer (EMMPRIN), is a M(r) approximately 58,000 glycoprotein which is located on the outer surface of human tumor cells and which interacts with fibroblasts to stimulate expression of several matrix metalloproteinases in the fibroblasts. In this study, we have used several approaches to isolate a complementary DNA encoding EMMPRIN. Several peptide sequences obtained from the isolated M(r) 58,000 glycoprotein are found in the translated complementary DNA clone, verifying its identity. Computer database searches indicate that EMMPRIN is a member of the immunoglobulin superfamily and that the deduced amino acid sequence of EMMPRIN is identical to that recently reported for human basigin and M6 antigen, molecules of previously undetermined biological function.

[Discourse on the establishment of rural medical course in Zouping County, Shandong province by Liang Shuming]

As early as 1930's, Mr. Liang Shuming established a sanitation hospital in the county experimental construction area of Zouping, Shandong province and designed a three-tier model for rural health care. He also explored the way of establishing the health care for rural maternity and children's school hygiene, public health care and itinerant medical care. All of these exert profound influence which is still active and feasible even today.

Upregulation of gap junctional communication and connexin43 gene expression by carotenoids in human dermal fibroblasts but not in human keratinocytes

Consumption of dietary carotenoids has been statistically associated with decreased risk of cancer at several anatomic sites. In a model murine system of carcinogenesis (the 10T1/2 assay), we have previously shown that carotenoids can inhibit chemically and physically induced neoplastic transformation. This action is strongly correlated with the ability of carotenoids to increase gap-junctional communication (GJC) by induction of connexin43 (Cx43) gene expression. Here we extend these studies to human foreskin-derived dermal fibroblasts and keratinocytes. In fibroblasts, beta-carotene and canthaxanthin at concentrations between 10(-5) and 3 x 10(-6) M were found to strongly enhance GJC in a dose- and time-dependent manner. This was accompanied by an increase in the number of immunofluorescent junctional plaques recognized by an anti-Cx43 antibody and by an increase in Cx43 protein level as determined by western blot analysis. No decrease in proliferation rates was detected by [H3]thymidine labeling. Human keratinocytes grown in monolayer culture did not respond to carotenoids in terms of GJC as measured by dye transfer, immunofluorescent analysis of Cx43 distribution, or Cx43 levels as measured by western blotting. Both cell types accumulated high levels of carotenoids. Because canthaxanthin, which has no known provitamin A activity in mammals, is as active in fibroblasts as is beta-carotene, the carotenoid with the highest provitamin A activity, the induction of GJC and Cx43 expression by carotenoids in human dermal fibroblasts seems unrelated to their provitamin A status. The lack of response of keratinocytes suggests differences in regulation of Cx43 expression or in carotenoid processing.

Maternal and fetal brain and plasma levels of cocaine and benzoylecgonine after acute or chronic maternal intravenous administration of cocaine

The effect of repeated i.v. administration of cocaine HCl (1.5, 3 or 6 mg/kg daily) from gestational day 8 through gestational day 18 was studied on maternal and litter parameters in the pregnant female Sprague-Dawley rat. These doses of cocaine had no significant effect on maternal weight gain or nutritional intake and did not significantly affect litter size. Levels of cocaine and its metabolite benzoylecgonine in the brain and plasma of the dams and their fetuses were measured on gestational day 18 at 1, 5, 20 or 60 min after a single injection or 11 daily i.v. injections of cocaine (6 mg/kg). The shape of the time courses for cocaine differed somewhat between dams and fetuses, with fetal plasma concentrations of cocaine initially being lower than those of their dams and then by 5 min becoming equivalent to those of their dams. Although plasma concentrations of cocaine soon equilibrated between dams and fetuses, plasma concentrations of benzoylecgonine did not. Interestingly, brain concentrations of cocaine did not differ between dams and fetuses. The most remarkable finding was that the relative distribution of cocaine between brain and plasma differed after chronic vs. acute treatment, with a relative shift in the distribution of cocaine from plasma to the brain in the fetuses, and with the exception of the earliest time point measured, in the dams after repeated dosing.

Lactate enhances sodium channel conductance in isolated guinea pig ventricular myocytes

Myocardial hypoxia and ischemia result in the production of lactate. To study the effect of lactate on the rapid Na+ current (INa), we used the whole cell voltage-clamp technique in enzymatically isolated guinea pig ventricular myocytes. Experiments were conducted at 16 degrees C. Extracellular Na+ concentration ([Na+]o) was maintained in control and test solutions and extracellular pH was 7.4. Lactate (4-10 mM, either sodium lactate or lactic acid) augmented INa in each of eight experiments, increasing the peak Na+ conductance from 75.4 to 84.7 nS (13-16% at all test voltages in the linear portion of the conductance curve). The voltage dependence of steady-state availability and the time course of inactivation remained unchanged. The increase in peak Na+ conductance was concentration dependent, with an apparent dissociation constant of 1.8 mM and Hill coefficient of 1.8. Lactate in the range of 1-10 mM did not significantly reduce the Ca2+ activity of test solutions. These effects of lactate were still observed in Mg(2+)-free test solutions and when the buffering capacity of internal solution was reinforced by increasing N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid concentration from 5 to 20 mM. In conclusion, lactate enhances INa via a mechanism that does not involve chelation of Ca2+ or Mg2+ or changes in intracellular pH. These effects of lactate on the Na+ channel might alter electrophysiological properties during myocardial ischemia and could protect the heart from ischemia-induced conduction abnormalities or, alternatively, could lead to arrhythmias.

Regulation of in vitro nucleic acid strand annealing activity of heterogeneous nuclear ribonucleoprotein protein A1 by reversible phosphorylation

Phosphorylation in vivo of several proteins in the mammalian heterogeneous nuclear ribonucleoprotein complex (hnRNP), including A1, has been observed and proposed as a regulatory step in pre-mRNA splicing [Maryland, S. H., Dwen, P., & Pederson, T. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 7764-7768]. We examined the ability of recombinant hnRNP protein A1 to act as a substrate for a number of purified Ser/Thr protein kinases in vitro. A survey of seven protein kinases showed that A1 was heavily phosphorylated by protein kinase C (PKC) and also was phosphorylated by casein kinase II, protamine kinase, and protein kinase A. In contrast, autophosphorylation-activated protein kinase and two forms of myelin basic protein kinase failed to phosphorylate A1. Proteolysis with trypsin and V8 protease revealed that PKC phosphorylates A1 at three main sites, two in the N-terminal domain (spanning residues 2-196) and one in the C-terminal domain (spanning residues 197-320). Amino acid sequencing revealed that these sites were Ser95, Ser192, and Ser199; phosphorylation at Ser192 was more abundant than at Ser95 and Ser199. Phosphorylation by PKC inhibited the strand annealing activity of A1. Protein phosphatase 2A, but not protein phosphatase 1, dephosphorylated A1 and reversed the inhibitory effect of PKC phosphorylation on the strand annealing activity. A conformational change in the C-terminal domain of A1 was observed upon PKC phosphorylation, and this was associated with a decrease in A1's affinity for single-stranded polynucleotides. The results are consistent with a role of phosphorylation of A1 in regulating its strand annealing activity in vivo.

Localization of mRNA for protein phosphatase 2A in the brain of adult rats

The gene expression for alpha and beta isoforms of type 2A protein phosphatase (PP2A-alpha and -beta) in the adult rat brain was examined by in situ hybridization analysis. No marked difference in the gene expression was discerned between the two isoforms in large portions of brain, except for the thalami in which the expression level for the alpha isoform was similar to that in the cerebral neocortex whereas that for the beta was lower than that in the neocortex. The gene expression was observed intensely in the piriform cortex, the cerebellar Purkinje and granule cell layers, and the hippocampal pyramidal and dentate granule cell layers, and the locus ceruleus, whereas the moderate levels of its expression were observed in the olfactory mitral cells and the pontine nuclei. The cerebral neocortex expressed the mRNA moderately to weakly without any laminar patterns, whereas the expression level in the caudate-putamen was very low. This expression pattern is basically similar to that of PP2C reported previously, except for the plexus choroideus and ependyma having no significant expression for PP2A.

The biological study of the cultured human lens epithelial cells in vitro

The human lens epithelial cells (HLE) cultured in vitro was established in normal and cataractous lenses. The biological feature, histological characteristics and the ultrastructure of the cultured HLE cells were investigated. The results reveal that the proliferative capacity of the cultured HLE cells is reversely proportional to the donor age; the cultured HLE cells has the limited proliferative capacity in vitro. The relieve of the contact inhibition is the effective trigger of the HLE cell proliferation. This research work is possible to make a basis for the further study of the regeneration of the lens and the roles of the lens epithelial cells in the development of the cataract.

Determination of wrist kinematics using a magnetic tracking device

The objective of this work is to present a method to determine the three-dimensional kinematics of the human wrist joint under physiological loading conditions using a magnetic tracking device. Euler angles were used to determine wrist extension-flexion, radial-ulnar deviation and supination-pronation. The screw displacement axis (SDA) method was used to describe the relative motion between carpal bones. Computer graphics were also used to obtain a better visualization of the three-dimensional motions of the carpal bones. This was accomplished by combining motion data and digitization data describing the geometry of the articular surfaces of the carpal bones. Geometric data included the locations of several points located on the articular surfaces forming the radio-scaphoid and radio-lunate joints. The SDA axes describing the motions of the capitate or the lunate or the scaphoid with respect to the radius during flexion-extension were found almost parallel to the medial-lateral direction. Translations along any SDA did not exceed 2 mm. One can thus consider the motion of each carpal bone as a pure rotation about a screw axis. Also, the SDA axis describing the motion of the capitate with respect to the radius was found to pass through the proximal end of the capitate. The graphical display of carpal motions shows that, as the wrist is flexed, the surface of the lunate within the radio-lunate articulation moves from palmar to dorsal. On the other hand, the palmar-dorsal location of the proximal surface of the scaphoid within the radio-scaphoid articulation remains almost unchanged.

[Studies on natural foci of tsutsugamushi disease of the autumn-winter type in Jiangsu]

Before 1986, tsutsugamushi disease was known only prevalent in south to Zhejiang Province in our country, belonged to the summer type and Leptotrombidium (L.) deliense was regarded as the main vector. In October 1986, the authors found this disease in Nanjing and carried out a series of studies in 1986-1992. The results were as follows: Tsutsugamushi disease was epidemic in Nanjing and north of Jiangsu (including: Dongtai, Haian, Rudong, Jinhu, Hanjiang, Jiangdu); belonged to the autumn-winter type; the main reservoir hosts were Apodemus agrarius, Rattus confucianus, R. norvegicus and Crocidura lasiura; the transmitting vector was L. (L.) scutellare; the pathogen of tsutsugamushi disease of the autumn-winter type-Rickettsia tsutsugamushi belonged to low-virulent strain, and could not easily be detected; after the inoculated mice were treated with diluted cyclophosphamide solution, 14 strains of R. tsutsugamushi have been isolated from rats, mites and patients; serological typing of their sera showed that they belonged to the Gilliam type; natural foci in Jiangsu could be divided into two types--flat land and hilly land.

Prenatal exposure to methadone delays the development of striatal cholinergic neurons

The effect of prenatal exposure to methadone via maternal osmotic minipumps on the expression of acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) has been studied by light microscopy in the striatum of male and female rats. At postnatal day 10, rats of both sexes exhibit reduced intensity of ChAT-immunoreactive staining in striatal neurons in the methadone-treated group in comparison to either untreated or water-treated controls. Although the number and distribution of ChAT-immunoreactive neurons appear to be similar across all three groups, the size (cross-sectional area) of these neurons is significantly smaller in the methadone-treated animals. By postnatal day 22, there are no differences in the ChAT immunoreactivity of striatal neurons between the water-treated and methadone-treated animals. The size of these neurons in female animals of both treatment groups is significantly larger than those of male animals in the same groups at postnatal day 22. AChE histochemical staining is qualitatively similar between treatment groups in both age groups. Thus, prenatal exposure to methadone appears to produce a delay in the expression of ChAT in striatal neurons. It remains to be demonstrated whether these differences are a direct effect of methadone exposure or are a consequence of neonatal withdrawal.

Therapeutic tumor-specific cell cycle block induced by methionine starvation in vivo

The ability to induce a specific cell cycle block selectively in the tumor could have many uses in chemotherapy. In the present study we have achieved this goal of inducing a tumor-specific cell cycle block in vivo by depriving Yoshida sarcoma-bearing nude mice of dietary methionine. Further, we demonstrate that methionine depletion also causes the tumor to eventually regress. The antitumor effect of methionine depletion resulted in the extended survival of the tumor-bearing mice. The mice on the methionine-deprived diets maintained their body weight for the time period studied, indicating that tumor regression was not a function of body weight loss. The data reported here support future experiments utilizing methionine depletion as a target for tumor-selective cell cycle-dependent therapy.

Mechanism of DmS-II-mediated pause suppression by Drosophila RNA polymerase II

Transcription elongation factor S-II mediates nascent transcript cleavage by RNA polymerase II (Reines, D. (1992) J. Biol. Chem. 267, 3795-3800). We have examined the mechanism of action of the Drosophila S-II analog, DmS-II, in a defined transcription system. Our results show that DmS-II is necessary and sufficient to activate nascent transcript cleavage by RNA polymerase II during transcription of a dC-tailed template. The pattern of transcripts resulting from prolonged action by DmS-II indicates that there are kinetic barriers to transcript shortening. During the cleavage reaction, the polymerase remains in register with the template strand and generates mainly nucleotide dimers. The ability of DmS-II to mediate transcript shortening resides in the carboxyl-terminal half of the protein. Our results support a model for pause suppression in which DmS-II binds to the paused polymerase, causes one cleavage event and is then released from the complex. Elongation by the polymerase then allows a second encounter with the pause site and a second chance of passing the site. Complete pause suppression may require multiple transcript shortening events for some polymerase molecules.

Phosphorylation and activation of protamine kinase by two forms of a myelin basic protein kinase from extracts of bovine kidney cortex

Two myelin basic protein kinases designated MBPK-1 and MBPK-2 were purified to apparent homogeneity from extracts of bovine kidney cortex. The purified preparations exhibited an apparent M(r) approximately 40,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and approximately 42,000 (MBPK-1) and 45,000 (MBPK-2) by gel permeation chromatography. Up to 0.4 and 1.8 mol of phosphoryl groups were incorporated per mol of MBPK-1 and MBPK-2, respectively, on threonines following incubation with ATP. Autophosphorylation, incubation with protein phosphatase 2A2 (PP2A2), CD45, or T-cell protein tyrosine phosphatase did not affect MBPK-1 activity. Autophosphorylation increased by about 3-fold MBPK-2 activity. This autophosphorylation and activation was reversed by PP2A2 but not by CD45 or T-cell protein tyrosine phosphatase. MBPK-1 and MBPK-2 displayed a positive reaction with an antibody to mitogen-activated protein kinase. Purified preparations of protamine kinase were activated by about 1.5-6-fold and, after inactivation with PP2A2, were reactivated by about 30% by MBPK-1 and MBPK-2. Activation and reactivation correlated with the incorporation, respectively, of 0.1-0.5 and 0.5 mol of phosphoryl groups/mol of the protamine kinase on serines. The results show that MBPK-1 and MBPK-2 are protamine kinase-activating kinases and suggest that MBPK-1 and MBPK-2 may be related to mitogen-activated protein kinase.

Purification and characterization of an autophosphorylation-activated protein serine threonine kinase that phosphorylates and inactivates protein phosphatase 2A

Protein phosphatase 2A2 is inactivated by phosphorylation following incubation with purified preparations of an autophosphorylation-activated protein kinase (Hong Guo and Zahi Damuni (1992) Proc. Natl. Acad. Sci. U.S.A. 90, 2500-2504). This protein kinase was purified about 250,000-fold from extracts of bovine kidney to apparent homogeneity. The purified preparations exhibited a single polypeptide of apparent M(r) approximately 36,000. Up to 1 mol of phosphoryl groups was incorporated per mol of the purified kinase following incubation with ATP. This autophosphorylation reaction (t1/2 approximately 0.5-1 min) was accompanied by a approximately 10-fold activation of the kinase. Autophosphorylation and activation were reversed by protein phosphatase 2A2 or the catalytic subunit of protein phosphatase 1. Phosphoamino acid analysis indicated that the kinase underwent autophosphorylation on threonines. The rate of autophosphorylation was independent of the concentration of the enzyme and a slope of 0.97 (gamma = 0.998) was obtained by van't Hoff's plot indicating that autoposphorylation was intramolecular. Relative to myelin basic protein, the enzyme exhibited about 8, 62, 130, 33, 5, and < 0.1% activity with histones H1, H2A, H2B, H3, and H4 and with glycogen synthase alpha, respectively. Heparin inhibited the activity of the enzyme half-maximally at about 20 micrograms/ml. The results indicate that this autophosphorylation-activated kinase is a new protein kinase.

Hypothermia blunts acetylcholine increase in CSF of traumatically brain injured rats

Activation of muscarinic acetylcholine (ACh) receptors contributes to the pathophysiological consequences of moderate experimental traumatic brain injury (TBI). Hypothermia (30 degrees C) provides protection in experimental TBI. We measured ACh levels in CSF and plasma 5 min after moderate fluid percussion TBI under normothermic or hypothermic conditions, because ACh in the CSF has been correlated with the severity of behavioral deficits after TBI. Three groups were examined: TBI with hypothermic brain (30 degrees C), TBI with normothermic brain (37 degrees C), or sham TBI with normothermic brain (37 degrees C). ACh concentrations in CSF were significantly higher in 37 degrees C TBI rats, but not in 30 degrees C TBI rats compared to shams. ACh concentrations in plasma did not differ between groups. These results suggest that a contributing factor to the neuroprotective effects of moderate hypothermia in TBI may be related to the reduction of excessive ACh levels in the central nervous system following injury.

Autophosphorylation-activated protein kinase phosphorylates and inactivates protein phosphatase 2A

Purified preparations of a distinct autophosphorylation-activated protein kinase from bovine kidney phosphorylated and inactivated purified preparations of protein phosphatase 2A2 (PP2A2) by about 80% with the autophosphorylation-activated protein kinase, protamine kinase, and 32P-labeled myelin basic protein as substrates. Analysis of incubations performed in the presence of 0.2 mM [gamma-32P]ATP by autoradiography following SDS/PAGE and by FPLC gel permeation chromatography on Superose 12 demonstrated that the catalytic subunit of PP2A2 was phosphorylated in the incubation mixtures containing the kinase and phosphatase. Up to 0.3 mol of phosphate groups was incorporated per mol of the catalytic subunit of PP2A2 following incubation with the kinase. This phosphorylation was enhanced about 5-fold in the presence of 0.4 microM microcystin-LR. In addition, up to 1 mol of phosphate groups was incorporated per mol of the PP2A2 subunit of apparent M(r) approximately 60,000 when microcystin-LR was included. Analysis by thin-layer chromatography indicated that PP2A2 catalyzed an autodephosphorylation reaction which was inhibited by microcystin-LR. Phospho amino acid analysis showed that the catalytic subunit of PP2A2 was phosphorylated on threonine residues by the autophosphorylation-activated protein kinase. Together with previous observations, the results suggest that inactivation of PP2A by phosphorylation catalyzed by the autophosphorylation-activated protein kinase could contribute to the marked increase in the phosphorylation of cellular proteins in response to insulin and other mitogens.

Effect of catecholamines on intracellular pH in sheep cardiac Purkinje fibres

1. It has been reported that catecholamines affect intracellular pH (pHi) in a number of tissues, generally by altering the kinetics of the Na(+)-H+ exchanger. We postulated that catecholamines might affect pHi in cardiac tissue. We tested this in resting sheep cardiac Purkinje fibres by measuring transmembrane potential and pHi with standard and H(+)-sensitive microelectrodes. 2. Adrenaline and the beta-adrenergic agonist isoprenaline, both 5.0 x 10(-6) M, resulted in depolarization and intracellular acidification (adrenaline, 0.03 +/- 0.01 pH units, n = 8, P = 0.005; isoprenaline, 0.08 +/- 0.01 pH units, n = 17, P = 0.0001). The alpha-adrenergic agonist phenylephrine, at concentrations up to 200 microM, had no significant effect on membrane potential or pHi. 3. Isoprenaline significantly attenuated the half-time (t0.5) for pHi recovery from intracellular acidification induced via the NH4Cl pulse technique. Isoprenaline also attenuated the hyperpolarization that is normally seen at the onset of pHi recovery. Phenylephrine slightly reduced the t0.5 for recovery, although the reduction did not reach statistical significance. 4. Forskolin, 7.5-10 x 10(-5) M, an agent that raises intracellular cyclic adenosine 3',5'-monophosphate (cyclic AMP), also induced depolarization and acidification, similar to that induced by adrenaline and isoprenaline. 5. In the presence of the Na(+)-H+ exchange blocker 5-dimethyl amiloride, 2-6 x 10(-5) M, isoprenaline-induced acidification was blunted but not abolished. When administered in Na(+)-free Tyrode solution, isoprenaline-induced acidification was also not abolished. Buffering power, tested using the NH4Cl method, was not decreased by isoprenaline, but rather, was slightly increased. Reversal of H+ driving force across the cell membrane from the normally inward direction to outward (achieved by increasing pHo to 8.3-8.5 and depolarizing the membrane with 10 mM K+ solutions) did not prevent intracellular acidification from occurring in the presence of isoprenaline. When glycolysis was inhibited by a 60 min exposure to glucose-free solution containing 5.5 mM 2-deoxyglucose, acidification by isoprenaline was nearly abolished. 6. We conclude that, in resting sheep Purkinje fibres, beta- but not alpha-adrenergic stimulation results in intracellular acidification and depolarization, probably mediated via an increase in cyclic AMP. beta- but not alpha-adrenergic stimulation slows the rate of recovery from intracellular acidification and blunts the hyperpolarization associated with this recovery. 7. The intracellular acidification appears to be due both to partial inhibition of Na(+)-H+ exchange and to stimulation of glycolysis by beta-adrenergic agents.

[Application of electron microscopy in the diagnosis of neoplasms]

The majority of neoplasms can be diagnosed by light microscopy, but in some cases the diagnosis remains ambiguous due to poor differentiation, even though special stainings have been employed. This paper presents 34 cases of neoplasms in which the tumors were diagnosed by electron microscopy. This includes distinguishing (1) anaplastic carcinoma from lymphoma; (2) anaplastic carcinoma from amelanotic melanoma; (3) APUDoma from other tumors; (4) different mesenchymal tumors. The diagnoses of 4 cases of malignant melanoma, 11 cases of APUDoma, 7 cases of poorly differentiated carcinoma or anaplastic carcinoma, 2 cases of non-Hodgkin's lymphoma, 9 cases of mesenchymal tumors and 1 cases of other tumors have been resolved by electron microscopy. It is obvious that in some cases, electron microscopy can be of help in establishing a correct diagnosis.

Gap-junctional protein connexin 43 is expressed in dermis and epidermis of human skin: differential modulation by retinoids

Retinoids are effective modulators of proliferation and differentiation of keratinocytes in vivo and in vitro. In mouse 10T1/2 cells, retinoid action on proliferation and neoplastic transformation is correlated with the upregulation of gap-junctional communication and expression of connexin 43 (Cx43). In the present study we have determined if retinoids induce similar effects on gene expression in human skin. Studies were conducted in intact skin and on cultured keratinocytes and dermal fibroblasts. In a clinical study, 2 weeks of treatment with 0.05% all-trans retinoic acid resulted in increased expression of Cx43 mRNA and protein in epidermis. Expression occurred predominantly in the suprabasal layer. Cultured cells exhibited a differential response to retinoic acid. In keratinocytes, increased expression of Cx43 occurred at low (10(-11) M) concentrations, whereas inhibition occurred at high (10(-7) M) concentrations; however, junctional communication, measured by dye transfer, was not altered over this concentration range. Dermal fibroblasts, in contrast, exhibited a dose-dependent increased expression of Cx43 at concentrations up to 10(-7) M retinoic acid and proportionately increased their junctional communication over this dose range. These data indicate that control of Cx43 gene expression by retinoids in human skin cells is complex. The production of gradients of junctional channels could play a role in the control of growth and differentiation in epidermis.