The chromatin structure of the mouse beta-2-microglobulin locus

Within the promoter regions of both major histocompatibility complex (MHC) class I genes and the beta 2-microglobulin (beta 2m) gene, there are a number of common regulatory elements suggesting co-ordinate control. However, there is also evidence to suggest that beta 2m and class I are differentially regulated, indicating that these genes may have distinct regulatory elements. We sought to explore this question by analysing DNase I hypersensitive (DH) sites flanking the beta 2m gene. Five DH sites have been found within the vicinity of the beta 2m gene. One of these sites (DH1) located within the promoter region, correlates with the transcriptional activity of beta 2m since it is weak in embryonal (beta 2m negative) cell lines. The remaining DH sites (2-5) are located downstream of the beta 2m gene. The most proximal downstream site, (DH2) located 5.5 kb from the last exon, was observed only in embryonal cell lines, indicating possible involvement in the downregulation of beta 2m. Furthermore, this site is markedly diminished in differentiated F9 cells. Possible roles for the remaining sites are discussed, in particular relationship to a second transcriptional unit identified in the vicinity. In addition, a similar analysis reveals a cluster of DH sites located downstream from the last exon of the human beta 2m gene.

Differential stimulation of protein kinase C activity by phorbol ester or calcium/phosphatidylserine in vitro and in intact synaptosomes

Activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate (PMA) was compared with calcium/phosphatidylserine (Ca/PS). The substrate specificity of PKC was more limited with PS/PMA. Substrates could be divided into three overlapping groups according to their relative level of phosphorylation: C1, relatively preferred substrates with Ca/PS, included dephosphin, histone, and peptide GS1-10. C2, relatively preferred with PS/PMA, included myelin basic protein and MARCKS. C3, substrates independent of activators. PS/PMA altered the Vmax of PKC for substrate, and decreased the Km for Mg2+. Differential substrate phosphorylation by PS/PMA also occurred for PKC isozymes resolved by hydroxylapatite chromatography and was most dramatic for PKC-alpha, which could no longer phosphorylate histone or GS1-12. Differential activities of PKC were also observed in synaptosol and in intact synaptosomes where PMA stimulated phosphorylation of MARCKS, but not dephosphin. It was further shown that dephosphin was indeed a substrate of PKC in the intact synaptosomes by use of a repolarization-dependent dephosphin phosphorylation assay. The differential PKC activities could also be distinguished by inhibitors. H-7 was equipotent, palmitoylcarnitine did not inhibit in vitro C2 phosphorylation, but inhibited dephosphin in intact synaptosomes, and sphingosine did not inhibit C1 substrates and was without effect on dephosphin in intact synaptosomes. Therefore PS/PMA alters or limits the substrate specificity of PKC, leading to a differential substrate phosphorylation in vitro and in intact synaptosomes and differential inhibitor sensitivity. The pattern of protein phosphorylation observed after PKC activation in intact cells will therefore be dependent upon the activator.

Potencies of protein kinase C inhibitors are dependent on the activators used to stimulate the enzyme

The aim was to examine systematically the potencies of protein kinase C inhibitors as a function of the kinase activator. Protein kinase C is activated by at least four stimulators: calcium plus phosphatidylserine (Ca/PS), phorbol 12-myristate 13-acetate plus PS (PS/PMA), arachidonic acid plus calcium (Ca/AA) and the synthetic peptide activator PCK530-558. With histone or GS1-12 as substrates, protein kinase C was maximally activated by Ca/PS, or to maxima of 62%, 89% or 82% with PS/PMA, Ca/AA or PKC530-558, respectively. One group of inhibitors, including H-7 and staurosporine, were equipotent, regardless of the activator. All other inhibitors showed variable selectivity, dependent upon the activator. A second group of inhibitors, including sphingosine and lipophosphoglycan, were eight or 200 times more potent for inhibition of PS/PMA-stimulated activity (relative to Ca/PS) and a third group, including retinal and palmitoylcarnitine, were 14 or 262 times more potent towards Ca/PS-stimulated activity. A final group (rhodamine 6G) was nine times more potent when Ca/AA was the activator. Similar results were obtained using the endogenous substrates dephosphin or MARCKS in synaptosol. Phosphorylation of MARCKS was stimulated by PS/PMA or Ca/PS, while phosphorylation of dephosphin was stimulated only by Ca/PS. The phosphorylation of either by Ca/PS-activated kinase was nine times more potently inhibited by palmitoylcarnitine, while phosphorylation of MARCKS by PS/PMA-activated kinase was 10 times more potently inhibited by sphingosine. H-7 inhibited both at similar concentrations. A model encompasses these differences in potency if the inhibitors are divided into four groups (A-D) according to their competitive inhibition with the appropriate activator or at the active site. The non-selective inhibitors interact at the active sites of protein kinase C (group A). The compounds which preferentially inhibit PS/PMA-activated kinase (sphingosine and lipophosphoglycan) are competitive inhibitors of PMA and 1,2-diacylglycerol (group B), those selective for Ca/PS-activated kinase (palmitoylcarnitine and retinal) are competitive with PS (group C) and those selective for Ca-AA activation (rhodamine 6G) are likely to be competitive with fatty acid (group D). Therefore, the effectiveness of protein kinase C inhibitors is dependent upon the activator employed.

Novel cell junctions induced by activating Thy-1-specific antibodies

KT16, like other anti-Thy-1 antibodies, induces T cell aggregation. Protein A-gold labelling shows the antibody to be concentrated along areas of intercellular contacts. Electron micrographs of KT16 treated T cells reveal a consistent type of junction between the cells. We demonstrate that this type of cell junction is Thy-1 specific, is predominantly the property of antibodies directed against a particular epitope, and is distinct from cellular aggregation caused by concanavalin A or anti-CD3 antibodies. The degree of adhesiveness induced by different anti-Thy-1 antibodies is related to their mitogenic capacity.

A quantitative method for measuring regional in vivo fatty-acid incorporation into and turnover within brain phospholipids: review and critical analysis

An experimental method and its associated mathematical model are described to quantitate in vivo incorporation rates into and turnovers of fatty acids (FAs) within stable brain metabolic compartments, particularly phospholipids. A radiolabeled FA is injected i.v. in a rat, and arterial plasma unacylated FA radioactivities and unlabeled concentrations are sampled until the animal is killed after 15 min, when the brain is analyzed biochemically or with quantitative autoradiography. Unbound unacylated label in blood easily crosses the blood-brain barrier; rapidly equilibrates in the unacylated FA, acyl-CoA and phosphatidate-diacylglycerol brain pools; then is incorporated into phospholipids and other stable metabolic compartments. Uptake and incorporation of labeled FAs are independent of cerebral blood flow at constant brain blood volume. Different labeled FAs enter specific sn positions of different brain phospholipids, suggesting that a combination of probes can be used to investigate metabolism of these phospholipids. Thus, [9,10-3-H]palmitate preferentially labels the sn1 position of phosphatidylcholine; [1-14C]arachidonate the sn2 positions of phosphatidylinositol and phosphatidylcholine; and [1-14C]docosahexaenoate the sn2 positions of phosphatidylethanolamine and phosphatidylcholine. The FA model provides an operational equation for rates of incorporation of FAs into brain phospholipids, taking into account intracerebral recycling and de novo synthesis of the FA, as well as entry into brain of FA from acylated blood sources. The equation is essentially independent of specific details of the proposed model, and can be used to calculate turnovers and half-lives of FAs within different phospholipid classes. For the model to be most applicable, experiments should satisfy conditions for pulse-labeling of the phospholipids, with brain sampling times short enough to minimize exchange of label between stable metabolic compartments. A 15-20 min sampling time satisfies these criteria. The FA method has been used to elucidate the dynamics of brain phospholipids metabolism in relation to brain development, brain tumor, chronically reduced auditory input, transient ischemic insult, axotomy with and without nerve regeneration, and cholinergic stimulation in animals with or without a chronic unilateral lesion of the nucleus basalis magnocellularis.

Evidence that the stimulation by arginine vasopressin of the release of adrenocorticotropin from the ovine anterior pituitary involves the activation of protein kinase C

These studies were undertaken to evaluate the role of protein kinase C (PKC) in the regulation by arginine vasopressin (AVP) of adrenocorticotropin (ACTH) secretion from the ovine anterior pituitary. AVP caused the rapid translocation of PKC from the cytosol to the cell membrane in ovine anterior pituitary cells that was maximal at 5 min. This phenomenon, which is a known concomitant of C-kinase activation, was produced to a greater extent by phorbol 12-myristate 13-acetate (PMA) but not by corticotropin-releasing factor (CRF). To determine whether AVP activated corticotrope PKC, we assessed the ability of three different PKC inhibitors (H-7, sphingosine, and retinal) to modify basal, AVP-, PMA-, and CRF-stimulated ACTH release. In addition to inhibiting the in vitro activity of purified PKC, each compound also caused in vitro inhibition of the protein kinase A (PKA) catalytic subunit, indicating that none could be considered to be a specific inhibitor of PKC and the PKA catalytic subunit. As determined by the mean IC50 values required for the in vitro inhibition of PKC and the PKA catalytic subunit, sphingosine was judged to be the most selective and H-7 the least selective PKC inhibitor. A 4 h exposure to each inhibitor caused a dose-dependent increase in basal ACTH release and attenuation of both AVP- and PMA-stimulated ACTH release. H-7 and retinal, in concentrations that caused a 20-50% inhibition of PKA, also attenuated CRF-stimulated ACTH release; however, this effect was not observed with sphingosine in concentrations that caused only a 10-20% inhibition of PKA. We conclude that: (1) AVP causes the direct activation of PKC in the ovine anterior pituitary and that C kinase activation is important in mediating the effect of AVP on ACTH release; (2) the finding that inhibition of PKC elevates ACTH suggests that basal ACTH secretion is also partly regulated by PKC; (3) since CRF does not cause PKC translocation in ovine anterior pituitary cells, it is unlikely that PKC plays a physiological role in the action of CRF on the corticotrope; (4) the finding that H-7 and retinal attenuate CRF-stimulated ACTH secretion suggests that CRF activates PKA in corticotropes.

Bone scanning

This article outlines the physical and biological bases of bone scanning and then describes the essential features of the technique. The principles underlying the clinical applications are listed, followed by a brief introduction to interpretation of the scan images.

Cholinoceptor regulation of cyclic AMP levels in bovine adrenal medullary cells

1. The regulation of adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels by cholinoceptors has been studied in cultured bovine adrenal medullary cells. 2. Acetylcholine (100 microM), nicotine (10 microM) and dimethylphenylpiperazinium (20 microM) each increased cellular cyclic AMP levels 2 to 4 fold over 5 min in the absence of phosphodiesterase inhibitors. The muscarinic agonist acetyl-beta-methylcholine (100 microM) had no effect either on its own or on the response to nicotine. The responses to acetylcholine and nicotine were unaffected by atropine (1 microM) but were abolished by mecamylamine (5 microM). 3. Cellular cyclic AMP increased transiently during continuous exposure to nicotine (1-20 microM), with the largest response seen after 5 min, a smaller response after 20 min, and no change in cyclic AMP levels seen after 90 or 180 min. The maximal response after 5 min stimulation was seen with 5-10 microM nicotine and the EC50 was about 2 microM. In contrast, extracellular cyclic AMP levels did not change after 5 or 20 min stimulation with nicotine, but increased slightly after 90 min and further after 180 min. 4. The cellular cyclic AMP response to nicotine (10 microM) was unchanged or weakly enhanced in the presence of the unselective phosphodiesterase inhibitor, isobutylmethylxanthine, and was unchanged in the presence of rolipram. Nicotine did not interact synergistically with low concentrations of forskolin. The response was however completely abolished in the absence of extracellular Ca2+.

Positional audiometry in the diagnosis of perilymphatic fistula

Fifty-eight cases with a presumptive clinical diagnosis of perilymphatic fistula (PLF) are described with the results of a positional audiometric test designed to detect the presence of air in the cochlea. All patients underwent tympanotomy and observations of the middle ear are recorded together with the results of treatment. A definite leak was found in 33 cases and none in 25, but grafting of the round and oval window was performed in all but 10 cases. Pure-tone audiometry was performed before and after a 30-minute period of positioning the patient horizontally with the affected ear uppermost. A change in audiometric thresholds was noted in the group where a presumptive diagnosis of PLF was made, including some of those not found to have leaks at operation. However these changes were not observed in the positional tests of a group of 22 patients with hearing losses attributable to other causes. Also, an abnormal air-bone gap was noted in the PLF group compared with the other group. Although the original two-frequency criteria of earlier studies applied to the positional test did not predict the operative findings (leak or no leak), new data on frequency specific changes are presented. It is possible that fistulas at the oval window may be associated with positional threshold change at 500 Hz, and those at the round window with changes at 8 kHz.

The effect of palate repair on otitis media with effusion

Cleft palate in children is very frequently associated with otitis media with effusion. In this prospective study of 150 cleft palate children aged between 2 and 18 months, the prevalence of otitis media with effusion at myringotomy before palate repair was 92 percent. Otoscopic and tympanometric follow-up assessments for 140 children indicate that there is minimal improvement in middle ear status after palate repair. The condition is persistent in 70 percent of children up to 4 years of age. Furthermore, there is no evidence that age at repair or type of cleft is influential. These findings have implications for otologic management of cleft palate children. Early routine unilateral ventilation to ensure adequate hearing but minimize the morbidity of ventilation tubes is advocated.

Treponema denticola and Porphyromonas gingivalis as prognostic markers following periodontal treatment

Subgingival plaque samples were collected from individuals with advanced periodontitis before and 3 to 11 weeks after scaling and root planing periodontal treatment. The plaque levels of Treponema denticola and Porphyromonas gingivalis antigens were measured before and after treatment by a quantitative immunoassay procedure using monoclonal antibodies specific for these oral bacteria. A decrease in mean levels of T. denticola (P less than .05) and P. gingivalis antigens (P less than .09) were observed following periodontal therapy. Improved health, as measured by a decrease in probing depth, was associated with a decrease in T. denticola antigen (P less than .05). These results suggest that the T. denticola levels of successfully treated sites decreased, while non-responding sites had levels of this microbial marker which were equal to or greater than the pre-treatment levels. These results provide additional evidence that T. denticola is associated with human adult severe periodontal disease, and can serve as a prognostic marker for disease recurrence.

Biochemical analysis of the mouse mammary tumor virus long terminal repeat product. Evidence for the molecular structure of an endogenous superantigen

Recent reports have shown that both exogenous and endogenous mouse mammary tumor viruses (MMTV) can encode superantigens. Transfection and transgenic studies have identified the open reading frame (ORF) present in the 3' long terminal repeat (LTR) as encoding superantigen function. In this study, we have used an in vitro translation system in an attempt to characterize the molecular nature of the protein encoded by the 3' ORF of Mtv-8. Using various constructs encoding full-length and truncated versions of the ORF product, we report that the hydrophobic region close to the amino terminus of the 36-kDa protein can function as a transmembrane domain. Protease digestion experiments also demonstrate that the protein has a type-II transmembrane conformation with an extra-cytoplasmic carboxy terminus. Since this hydrophobic region is conserved between all known MMTV, we speculate that LTR ORF, including those proposed to encode the minor lymphocyte stimulatory antigens, are also capable of encoding type-II transmembrane glycoproteins. The polymorphism between MMTV LTR ORF products, which correlates with deletion phenotypes, is predominantly in the carboxy-terminal extracellular region, consistent with a major role in interaction with the T cell receptor.

Hepatic perfusion index: a multicentre trial

The reproducibility and accuracy of the hepatic perfusion index (HPI) was examined by consideration of in vitro and in vivo factors. A phantom was used to simulate liver blood flow and data acquired on nine gamma cameras. Dynamic hepatic scintigraphy was undertaken on 28 patients at two centres and values obtained for the HPI. Results from the phantom study showed good agreement between the nine cameras and also with the HPI values predicted from the measured phantom flow rates. The results of the patient study indicated a high degree of conformity between observers (r = 0.95, S.E = 0.03) but poorer correlation between the HPI values from the two centres (r = 0.67, S.E. = 0.09). These results imply that centres wishing to use HPI clinically should establish their own range of normality.

Endogenous ligands selecting T cells expressing particular V beta elements

It has recently become clear that the minor lymphocyte stimulatory antigens (Mls) and other endogenous ligands which lead to the partial or total deletion of T cells bearing particular V beta segments are encoded by mouse mammary tumor virus (MMTV). We review here the genetic analyses of multiple V beta 11 and V beta 3 deletion ligands and demonstrate the involvement of MMTV in all examples. Several features of Mls and the V beta 11/V beta 3 deleting ligands identify them as members of the superantigen family. Bacterial superantigens are known to bind both MHC class II and the TCR in regions distinct from conventional peptide antigens. Within the MMTV genome, the 3' LTR has been identified as encoding superantigen function. We present data demonstrating that in vitro translation identifies the major product of the open reading frame (ORF) within the 3' LTR as a type II integral membrane glycoprotein. It is proposed that the type II membrane glycoprotein interacts with MHC and TCR in a manner analogous to the bacterial superantigens and distinct from conventional peptide antigen. Several unanswered questions regarding superantigen action remain; what determines total or partial deletion? How is Mls transferred between cells? These questions are addressed in the discussion.

Radionuclide limb blood flow in peripheral vascular disease: a review of 1100 measurements

Radionuclide limb blood flow measurements using 99Tcm-labelled human serum albumin and a gamma camera have been performed on normal volunteers and on patients with suspected or confirmed peripheral arterial disease. The normal range of flow was found to be 10.0-22.3 ml per 100 ml tissue per min. Flow in the symptomatic legs of patients with arterial disease varied from 9.0 ml per 100 ml tissue per min in mild claudication to less than 1.0 ml per 100 ml tissue per min in rest pain. The technique has been used as an initial screening procedure, to resolve diagnostic problems, to measure objectively the treatment response and to assess patients with critical ischaemia. The results of 1100 measurements are reported and the clinical utility in routine vascular surgical practice is discussed.

The role of protein kinase C and its neuronal substrates dephosphin, B-50, and MARCKS in neurotransmitter release

This article focuses on the role of protein phosphorylation, especially that mediated by protein kinase C (PKC), in neurotransmitter release. In the first part of the article, the evidence linking PKC activation to neurotransmitter release is evaluated. Neurotransmitter release can be elicited in at least two manners that may involve distinct mechanisms: Evoked release is stimulated by calcium influx following chemical or electrical depolarization, whereas enhanced release is stimulated by direct application of phorbol ester or fatty acid activators of PKC. A markedly distinct sensitivity of the two pathways to PKC inhibitors or to PKC downregulation suggests that only enhanced release is directly PKC-mediated. In the second part of the article, a framework is provided for understanding the complex and apparently contrasting effects of PKC inhibitors. A model is proposed whereby the site of interaction of a PKC inhibitor with the enzyme dictates the apparent potency of the inhibitor, since the multiple activators also interact with these distinct sites on the enzyme. Appropriate PKC inhibitors can now be selected on the basis of both the PKC activator used and the site of inhibitor interaction with PKC. In the third part of the article, the known nerve terminal substrates of PKC are examined. Only four have been identified, tyrosine hydroxylase, MARCKS, B-50, and dephosphin, and the latter two may be associated with neurotransmitter release. Phosphorylation of the first three of these proteins by PKC accompanies release. B-50 may be associated with evoked release since antibodies delivered into permeabilized synaptosomes block evoked, but not enhanced release. Dephosphin and its PKC phosphorylation may also be associated with evoked release, but in a unique manner. Dephosphin is a phosphoprotein concentrated in nerve terminals, which, upon stimulation of release, is rapidly dephosphorylated by a calcium-stimulated phosphatase (possibly calcineurin [CN]). Upon termination of the rise in intracellular calcium, dephosphin is phosphorylated by PKC. A priming model of neurotransmitter release is proposed where PKC-mediated phosphorylation of such a protein is an obligatory step that primes the release apparatus, in preparation for a calcium influx signal. Protein dephosphorylation may therefore be as important as protein phosphorylation in neurotransmitter release.

Dephosphin, a 96,000 Da substrate of protein kinase C in synaptosomal cytosol, is phosphorylated in intact synaptosomes

A 96,000 dalton phosphoprotein, called dephosphin, is phosphorylated in intact synaptosomes from rat brain and is rapidly dephosphorylated upon depolarisation-dependent calcium entry. A 96,000 dalton phosphoprotein is also a substrate of protein kinase C in synaptosomal cytosol, and the aim of the study was to determine whether the two proteins may be the same. Dephosphin in intact synaptosomes and the 96,000 dalton protein kinase C substrate comigrated on polyacrylamide gels. Both phosphoproteins had identical phosphopeptide maps after digestion with V8 protease. Both phosphoproteins ran on isoelectric focussing gels with a pI of 6.3-6.7 and focussed as a series of 5-6 spots. Both proteins were phosphorylated exclusively on serine. Both proteins could be resolved into a doublet on longer polyacrylamide gels. The two subunits were of 96 and 93 kDa in both phosphorylation conditions and had dissimilar phosphopeptide maps. However, phosphopeptide maps of either the 96 or 93 kDa subunits were identical in intact synaptosomes compared with synaptosomal cytosol. These results show that a phosphoprotein phosphorylated in intact synaptosomes and a 96,000 dalton protein kinase C substrate from rat brain synaptosomal cytosol are the same, and raise the possibility that protein kinase C is the protein kinase responsible for dephosphin phosphorylation in intact synaptosomes.

Development and evaluation of a presurgical preparation program

Three presurgical preparation programs were developed and evaluated in an Australian hospital utilizing an additive component design. The component basic to all three preparation programs was modeling. This technique was compared with the additional components of teaching child coping skills and parent coping skills via videotape. Subjects were 28 children between the ages of 4 and 13 years who were scheduled for elective surgery. Anxiety of both the children and parents was assessed by self-report and behavior observation. Results indicated that there was no further anxiety reduction by the addition of child and parent coping skills. Results are discussed in terms of the viability of teaching coping skills via videotape particularly to parents. Methodological difficulties associated with research in this area are examined.

Hepatic perfusion index (HPI) in mesenteric angina and following successful revascularization

This is a case report of a 45 year old man who had previously undergone a small bowel resection for acute mesenteric ischaemia. He subsequently suffered from mesenteric angina due to stenosis of the origin of the superior mesenteric artery and intermittent claudication due to aorto-iliac atheroma. The patient underwent a successful aorto-bifemoral Y graft and small bowel revascularization with a saphenous vein graft between the Y graft and the accessible proximal portion of the superior mesenteric artery. Before vascular reconstruction, the hepatic perfusion indices (HPI) in both the fasted and fed states were elevated; after mesenteric revascularization the HPI values were substantially lowered. The hepatic perfusion index may, by demonstrating functional abnormality, be useful in the diagnosis of mesenteric ischaemia and also in the assessment of treatment. Further evaluation of HPI in patients with suspected mesenteric ischaemia is therefore required.

MDL 27,032 relaxes vascular smooth muscle and inhibits protein kinase C

The smooth muscle relaxant effect of MDL 27,032, 4-propyl-5-(4-pyridinyl)-2(3H)-oxazolone, was studied in vitro using strips of femoral arteries and saphenous veins from dogs and trachea from guinea pigs. MDL 27,032 (10(-6)-10(-3) M) produced a concentration-dependent relaxation of arterial and venous strips contracted by carbachol. MDL 27,032 also antagonized contractions of arterial and venous strips produced by phorbol 12,13-dibutyrate (PDB), a protein kinase C activator, both in normal-Ca2+ and zero-Ca2+ medium. The compound inhibited protein kinase C in soluble extracts prepared from saphenous veins of dogs, with an IC50 value of 36.6 microM. MDL 27,032 was more effective against the contractions produced by phenylephrine and serotonin than by KCl in arteries, but no such selectivity was noted in veins. MDL 27,032 (10(-3) M) also inhibited accumulation of inositol phosphates in femoral artery but not in saphenous vein, and this effect may have contributed to the arterial-relaxant effect. Because the vascular smooth muscle relaxant effect of MDL 27,032 was endothelium independent, did not involve blockade of alpha-adrenoceptors or inhibition of cyclic nucleotide phosphodiesterases, stimulation of beta-adrenergic receptors, stimulation of adenosine A2-receptors, or activation of K+ channels, these data suggest that the relaxant effects of MDL 27,032 primarily involve inhibition of protein kinase C.