Peptide sequence analysis and molecular cloning reveal two calcium pump isoforms in the human erythrocyte membrane

The sequence of more than 1,000 amino acid residues, derived from two different isoforms, has been determined from peptides generated from purified human erythrocyte membrane Ca2(+)-ATPase (hPMCA). Several of these peptide sequences correspond to the previously reported, cDNA deduced sequence of the "teratoma" Ca2+ pump isoform hPMCA1 (Verma, A. K., Filoteo, A. G., Stanford, D. R., Wieben, E. D., Penniston, J. T., Strehler, E. E., Fischer, R., Heim, R., Vogel, G., Matthews, S., Strehler-Page, M.-A., James, P., Vorherr, T., Krebs, J., and Carafoli, E. (1988) J. Biol. Chem. 263, 14152-14159). The complete primary structure of a novel isoform (hPMCA3) has been determined by molecular cloning and nucleotide sequencing of its corresponding cDNA. This new member of the plasma membrane Ca2+ pump family consists of 1,205 amino acid residues with a calculated Mr of 133,930, and it shows 88% similarity (75% identity) with the previously sequenced pump isoform. Specific probes detect major mRNA species of 5.6 kilobases for hPMCA1, and of 7.5 kilobases for hPMCA3, on Northern blots of human K562 erythroleukemic cell RNA. A large number of peptide sequences match perfectly with only one or the other of these isoforms and all peptides (with 6 exceptions corresponding to a contaminant protein or to a third minor Ca2+ pump isoform) are found in either only one or in both of the isoforms. The two erythrocyte Ca2+ pumps display high sequence divergence in a few localized regions that may determine isoform-specific functional specializations; for example, the putative extracellular loop separating transmembrane domains 1 and 2, the highly negatively charged region previously suggested to be involved in Ca2+ binding, and the site of cAMP-dependent protein kinase phosphorylation.

Increase in a 55-kDa keratin-like protein in the nuclear matrix of rat liver cells during proliferative activation

We have identified a protein (p55) with a molecular weight of 55 kDa and a pI of 6.2, which was strongly increased in the nuclear matrix of rat liver cells during proliferative activation. This protein is highly insoluble since it could not be solubilized either by detergents or by alkaline extraction. We have obtained three partial amino acid sequences which revealed that p55 has a high homology with cytokeratins. Polyclonal antibodies raised against p55 were used to carry out Western blot and immunocytochemical studies which indicated that p55 was localized only in the nuclei, specifically in the nuclear matrix. Autoradiographic experiments revealed that not all the cells presenting an increase in p55 incorporated [3H]thymidine, indicating that this protein is not related to DNA replication. Immunocytochemical studies also revealed that during mitosis p55 is localized surrounding the chromosomes and associated with the mitotic apparatus, suggesting that p55 is involved in the separation of chromosomes during cell division.

M.R. imaging of the knee: a prospective trial using a low field strength magnet

A double blind prospective study involving fifty patients was performed to assess the diagnostic accuracy of knee MR Imaging using a 0.3 Tesla low field strength scanner. The study compared MR Imaging with arthroscopy. The overall accuracy found for the detection of meniscal tears was 92% and cruciate ligament tears 95%. These results compare favourably with other diagnostic modalities including knee arthroscopy. MR Imaging is good at showing meniscal lesions, especially cleavage tears, though some bucket-handle tears produced no MR abnormality. MR Imaging is very accurate at demonstrating complete cruciate ligament tears. Partial cruciate ligament tears often produced no positive MR findings and in no patients could any features be found to indicate ligamentous laxity.

Interaction of calmodulin with the calmodulin binding domain of the plasma membrane Ca2+ pump

Peptides corresponding to the calmodulin binding domain of the plasma membrane Ca2+ pump (James et al., 1988) were synthesized, and their interaction with calmodulin was studied with circular dichroism, infrared spectroscopy, nuclear magnetic resonance, and fluorescence techniques. They corresponded to the complete calmodulin binding domain (28 residues), to its first 15 or 20 amino acids, and to its C-terminal 14 amino acids. The first three peptides interacted with calmodulin. The K value was similar to that of the intact enzyme in the 28 and 20 amino acid peptides, but increased substantially in the shorter 15 amino acid peptide. The 14 amino acid peptide corresponding to the C-terminal portion of the domain failed to bind calmodulin. 2D NMR experiments on the 20 amino acid peptides have indicated that the interaction occurred with the C-terminal half of calmodulin. A tryptophan that is conserved in most calmodulin binding domains of proteins was replaced by other amino acids, giving rise to modified peptides which had lower affinity for calmodulin. An 18 amino acid peptide corresponding to an acidic sequence immediately N-terminal to the calmodulin binding domain which is likely to be a Ca2+ binding site in the pump was also synthesized. Circular dichroism experiments have shown that it interacted with the calmodulin binding domain, supporting the suggestion (Benaim et al., 1984) that the latter, or a portion of it, may act as a natural inhibitor of the pump.

Nature and site of phospholamban regulation of the Ca2+ pump of sarcoplasmic reticulum

The rapid removal of Ca2+ ions from the cytosol, necessary for the efficient relaxation of cardiac muscle cells, is performed by the Ca2+-pumping ATPase of the sarcoplasmic reticulum. The calcium pump is activated by cyclic AMP- and calmodulin-dependent phosphorylation of phospholamban, an integral membrane protein of the sarcoplasmic reticulum. Using a heterobifunctional crosslinking agent which can be cleaved and photoactivated, we provide evidence for a direct interaction between the two proteins. Only the non-phosphorylated form of phospholamban interacts with the ATPase, demonstrating that phospholamban is an endogenous inhibitor that is removed from the ATPase by phosphorylation. Non-phosphorylated phospholamban interacts only with the calcium-free conformation of the ATPase and is released when it is converted to the calcium-bound state. We localized the site of interaction to a single peptide isolated after cyanogen bromide cleavage of the ATPase. The peptide derives from a domain just C-terminal to the aspartyl phosphate of the active site. This domain is unique to ATPases of the sarcoplasmic reticulum in that it has no homology with any other phosphorylation-type ion pump. The domain occurs in both slow- and fast-twitch isoforms of the ATPase, even though phospholamban is not expressed in fast-twitch muscles.

The calmodulin binding domain of the plasma membrane Ca2+ pump interacts both with calmodulin and with another part of the pump

Synthetic peptides corresponding to the calmodulin-binding domain of the human erythrocyte Ca2+ pump were prepared representing residues 2-29 (C28W), 2-21 (C20W), 2-16 (C15W), and 16-29 (C14) of the sequence (James, P., Maeda, M., Fisher, R., Verma, A. K., Krebs, J., Penniston, J. T., and Carafoli, E. (1988) J. Biol. Chem. 263, 2905-2910). Peptides C28W, C20W, and C15W bound to calmodulin with an apparent 1:1 stoichiometry in the presence of Ca2+ and inhibited the activation of the Ca2+ pump by calmodulin, while C14 was ineffective. Substituting tyrosine (C28Y) or alanine (C28A) for the tryptophan residue lowered the affinity for calmodulin. The estimated Kd values for the calmodulin-peptide complexes were 0.1 nM for C28W, 5-15 nM for C20W, C28Y, and C28A, and 700-1700 nM for C15W. The Ca2+ pump in inside-out erythrocyte membrane vesicles was activated by proteolytic removal of the endogenous calmodulin-binding domain. Addition of C20W or C28W then inhibited calmodulin-independent Ca2+ transport, while a calmodulin-binding peptide from another enzyme had no effect. The inhibition of the pump by C20W was purely competitive with Ca2+, while C28W decreased the Vmax and increased the K1/2 for Ca2+, restoring the pump activity nearly to its low basal level. The results suggest that a calmodulin-binding peptide from any enzyme has two kinds of specificity: it shares with peptides from other enzymes the ability to bind to calmodulin, but only it has the specificity to interact with its own (proteolytically activated) enzyme.

Reproductive, developmental, and genetic toxicology of ioversol

The authors examined the reproductive, developmental, and genetic toxicity of ioversol in several in vivo and in vitro systems. In Segments I, II, and III reproductive toxicity studies, ioversol did not produce teratogenic effects in either rats or rabbits at daily intravenous dose levels of up to 3.2 g I/kg/day. Daily intravenous injections in male and female rats did not adversely affect fertility or reproductive function. Offspring derived from dams treated with ioversol also developed and reproduced in a normal fashion. Four genetic toxicity studies employing bacterial and mammalian assay systems, and using both in vitro and in vivo methods, indicated that ioversol did not possess mutagenic or clastogenic activity.

Modulation of erythrocyte Ca2+-ATPase by selective calpain cleavage of the calmodulin-binding domain

The activity of the membrane-bound and the purified erythrocyte Ca2+-ATPase in the absence of calmodulin was stimulated by calpain digestion but could be further increased to maximal levels by calmodulin (CaM). Thus, CaM sensitivity was retained by the digested ATPase, at least at short times of incubation. In membranes digested at higher temperatures and in the purified ATPase digested at higher calpain/ATPase ratios, the ATPase became fully activated. The membrane-bound and the purified 138-kDa ATPase were converted by calpain to a fragment of approximately 124 kDa which still bound CaM and could be isolated on CaM columns when proteolysis occurred slowly but not when it occurred rapidly. Carboxypeptidase digestion of the purified enzyme and of its fragment of about 124 kDa has shown that calpain attacked the CaM-binding domain near the C terminus of the ATPase. This has also been supported by digestion of the purified enzyme and of its fragment of about 124 kDa. A first cut occurred in the middle of the domain producing a fragment of about 14 kDa and a (CaM-binding) fragment of about 124 kDa. A second cut closer to the N terminus of the domain also produced a fragment of about 124 kDa and accounted for the loss of CaM binding at prolonged times of incubation of the ATPase with calpain.

Hydrophobic binding of the ectodomain of influenza hemagglutinin to membranes occurs through the "fusion peptide"

Toward elucidating molecular details of virus-induced membrane fusion, we have studied the low pH-triggered interaction of the bromelain-solubilized ectodomain of influenza hemagglutinin with liposomes. Polypeptide segments which insert into the apolar phase of the lipid bilayer were first labeled specifically using either of the two membrane-restricted carbene-generating reagents, 3-(trifluoromethyl)-3-([125I]iodophenyl)diazirine and 1-palmitoyl-2-[11-[4-[3-(trifluoromethyl)diazirinyl]phenyl] undecanoyl]-sn-glycero-3-phosphorylcholine, and were then identified on the basis of cyanogen bromide and 2-(2-nitrophenylsulfenyl)-3-methyl-3'-bromoindolenine-skatole fragment analysis and Edman degradations. Here, we demonstrate that the hydrophobic interaction is mediated solely by the so-called "fusion peptide" which corresponds to the NH2-terminal segment of the BHA2 subunit of nature influenza hemagglutinin. Predominant sites of labeling within that segment were Phe-3, Ile-6, Phe-9, Trp-14, Met-17, and Trp-21. The average 3-4 residue spacing between consecutive labeled amino acid side chains suggests a helical structure of that segment with an amphiphilic character.

Isolation and NH2-terminal amino acid sequences of rat serum carrier proteins for insulin-like growth factors

Three N-glycosylated carrier proteins (CP) for insulin-like growth factors (apparent molecular weights 30-32, 42 and 45 kDa) were isolated from adult rat serum. They share the same amino terminus (up to amino acid 31) and are constituents of the growth hormone-dependent native 150-200 kDa IGF carrier complex. Residues 12-31 display 60 and 50% sequence homology, respectively, to residues 2-21 of fetal rat and to residues 4-22 of a human amniotic fluid IGF carrier protein. No homology exists with the type I or II IGF receptors. Adult rat serum also contains a fourth IGF CP (24 kDa) whose 9 NH2-terminal amino acids are identical to those of the fetal form. Our findings suggest that the three N-glycosylated components originate from the same IGF carrier protein (adult form) and that the 24 kDa protein is a separate (fetal) species.

Complete primary structure of human and rabbit lactase-phlorizin hydrolase: implications for biosynthesis, membrane anchoring and evolution of the enzyme

We report the primary structures of human and rabbit brush border membrane beta-glycosidase complexes (pre-pro-lactase-phlorizin hydrolase, or pre-pro-LPH, EC 3.2.1.23-62), as deduced from cDNA sequences. The human and rabbit primary translation products contain 1927 and 1926 amino acids respectively. Based on the data, as well as on peptide sequences and further biochemical data, we conclude that the proteins comprise five domains: (i) a cleaved signal sequence of 19 amino acids; (ii) a large 'pro' portion of 847 amino acids (rabbit), none of which appears in mature, membrane-bound LPH; (iii) the mature LPH, which contains both the lactase and phlorizin hydrolase activities in a single polypeptide chain; (iv) a membrane-spanning hydrophobic segment near the carboxy terminus, which serves as membrane anchor; and (v) a short hydrophilic segment at the carboxy terminus, which must be cytosolic (i.e. the protein has an Nout-Cin orientation). The genes have a 4-fold internal homology, suggesting that they evolved by two cycles of partial gene duplication. This repetition also implies that parts of the 'pro' portion are very similar to parts of mature LPH, and hence that the 'pro' portion may be a water-soluble beta-glycosidase with another cellular location than LPH. Our results have implications for the decline of LPH after weaning and for human adult-type alactasia, and for the evolutionary history of LPH.

Elucidation of alloantibodies in autoimmune haemolytic anaemia

Forty-one patients with autoimmune haemolytic anaemia (AIHA), who had free antibody in their sera, were investigated for the presence of alloimmune erythrocyte antibodies using the ZZAP autoabsorption technique. Patients were subdivided into three risk categories: (I) no prior pregnancy or transfusion; (II) history of pregnancy and/or one to five transfusions; and (III) greater than 5 transfusions. A total of 13 (32%) of the 41 patients exhibited significant alloantibodies. Of 11 category-I patients 2 (18%) had significant alloantibodies. Eight (31%) of the 26 category-II patients had significant alloantibodies and 3 (75%) of the 4 category-III patients had significant alloantibodies after absorption. The majority showed Rh specificity: anti-E(8), -C(3), -Cw(1). Anti-K was found in 6 samples and 1 had anti-Fya. Alloantibodies had not been suspected prior to autoabsorption in 10 (77%) of the 13 patients with alloantibodies. These findings underline the importance of performing autoabsorption in AIHA when free autoantibody is present in the serum. Additionally, Rh phenotyping performed on ZZAP-treated cells showed complete agreement with that ascertained using pure IgM Rh typing sera and untreated cells.

Continuous cisplatin (24-hour) and 5-fluorouracil (120-hour) infusion in recurrent head and neck squamous cell carcinoma

Cisplatin and 5-fluorouracil (5-FU) has been reported to be one of the most active chemotherapeutic regimens in recurrent head and neck squamous cell carcinoma. In this study, 21 patients with recurrent head and neck squamous cell carcinoma received a combination of cisplatin given as a 100 mg/m2 continuous infusion over 24 hours and 5-FU given as a 1000 mg/m2 24-hour continuous infusion for 120 hours. Toxicity was evaluated in all patients, and response and survival were evaluated 20 patients. There were two complete remissions (10%) and three partial remissions (15%) for a major response of 25%. Overall survival for the complete responders was 79+ and 61+ weeks, respectively. Median survival for all patients was 36 weeks. Toxicity consisted of moderate to severe nausea and vomiting in 14 patients (66%), mucositis in 14 patients (66%), granulocytopenia of less than 1000/microliter in 11 patients (52%), objective peripheral neuropathy in one patient (4.7%), and nephrotoxocity in one patient (4.7%). We conclude that the efficacy of 24-hour cisplatin infusion and 120-hour 5-FU infusion in the treatment of recurrent head and neck squamous carcinoma is not superior to the efficacy of single agent trials reported in the literature.

Identification and primary structure of a calmodulin binding domain of the Ca2+ pump of human erythrocytes

Exposure of the purified Ca2+ pump of human erythrocytes to chymotrypsin led to the rapid loss of calmodulin activation. A fragment of about 12 kDa was removed from the ATPase in 1-2 min. Blotting experiments with 125I-labeled calmodulin showed that this fragment contains the calmodulin binding region. The remainder of the ATPase molecule was degraded to a number of fragments ranging from 3 to 120 kDa; none of them bound calmodulin. To isolate the calmodulin binding domain, calmodulin which had been coupled to the Denny-Jaffe reagent (a cleavable radioactive photoaffinity cross-linker) was allowed to bind to the Ca2+ pump. After illumination to couple the cross-linker to the pump, the cleavable bond was split and the calmodulin removed, leaving the pump radioactively labeled. This pump was digested with chymotrypsin, and the products were separated by gel permeation chromatography. The only radioactive peak (migrating at about 12 kDa) was further purified on reverse-phase high pressure liquid chromatography (HPLC). Amino acid analysis showed the fragment to have a minimal molecular mass of 12.4 kDa and to contain a single methionine. After attempts to sequence the peptide directly failed. CNBr digestion was carried out on the labeled ATPase, producing both soluble and insoluble labeled material. After reverse-phase HPLC purification of the soluble material, a single radioactive peak was collected. Its sequence was (Formula: see text). A portion of this peak was passed through a microcalmodulin column; it bound in the presence of Ca2+ and was eluted by EDTA, and by a mixture of EDTA and urea. Staphylococcal V8 protease digestion of the eluted peak produced the same sequence as shown above, but starting at Leu-2 and ending at Glu-32. Structural analysis of this peptide showed that it shares features with the calmodulin binding domains of other enzymes which are regulated by calmodulin.

The amino acid sequence of the phosphorylation domain of the erythrocyte Ca2+ ATPase

The amino acid sequence of a peptide isolated from a CNBr digest of the erythrocyte Ca2+ ATPase has been determined. It contains a highly conserved phosphorylation site sequence common to all aspartyl-phosphate forming ion motive ATPases which have been sequenced so far.

Partial purification and characterization of porcine platelet-derived growth factor (PDGF)

Platelet derived growth factor (PDGF) has been partially purified from porcine platelets. Purification steps included heparin-agarose chromatography of the material released by thrombin-stimulated washed porcine platelets and Blue-Sepharose chromatography. Preparative isoelectric focusing showed that isoelectric point of porcine PDGF is at pH 10.0-11.0 and elution experiments from sodium dodecyl sulfate (SDS) polyacrylamide gels indicated that its molecular weight is close to 30 kD. The immunoglobulin fraction prepared from anti-human PDGF serum inhibited the mitogenic activity of porcine PDGF. These experiments suggest a homology of porcine and human PDGF. Porcine platelet factor 4 and porcine platelet basic protein were devoid of significant mitogenic activity.

Purification of two heparin-binding proteins from porcine platelets and their homology with human secreted platelet proteins

Two heparin-neutralizing proteins secreted by thrombin-stimulated platelets were purified to homogeneity by means of heparin-agarose affinity chromatography. These proteins, termed porcine platelet basic protein (PBP) and porcine platelet factor 4 (PF4), were eluted from a heparin-agarose column at 0.6-0.9 M NaCl and at 1-1.4 M NaCl, respectively. The molecular weight of porcine platelet basic protein was 7,000-7,700 daltons, as estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and amino acid analysis. The isoelectric point of this protein was at pH 9.0. The amino acid composition of porcine platelet basic protein resembled that of human low affinity platelet factor 4 (LA-PF4), except that the porcine protein did not contain tyrosine. The molecular weight of porcine platelet factor 4 ranged from 10,000 (estimated from amino acid analysis) to 14,000 (estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis). The amino acid compositions of human platelet factor 4 and of porcine platelet factor 4 were similar. Monospecific antibodies against porcine platelet factor 4 and porcine platelet basic protein were raised in rabbits. Competitive radioimmunoassay demonstrated a low but significant immunologic cross-reactivity between human and porcine platelet factor 4, and between porcine platelet basic protein and a group of human secreted platelet proteins that bind to heparin with low affinity (beta-thromboglobulin [beta TG] and low affinity platelet factor 4). Experiments with direct immuno-precipitation of 125I-labeled antigens suggested that all four proteins investigated (human platelet factor 4, porcine platelet factor 4, human low affinity platelet factor 4 or human beta-thromboglobulin, and porcine platelet basic protein) share common antigenic determinants. However, there was a higher degree of immunologic cross-reactivity between heterologous antigens with similar heparin binding affinity (human platelet factor 4 and porcine platelet factor 4) than between heterologous antigens with different binding affinity (human platelet factor 4 and porcine platelet basic protein). In conclusion, our finding suggests a significant structural homology among the four proteins.

Effect of heparin on the in vivo release and clearance of human platelet factor 4

Intravenous injection of heparin (100 U/kg) into normal volunteers resulted in an increase of platelet factor 4 (PF4) level in platelet-poor plasma from a mean value of 18.1 +/- 6.6 ng/ml before the injection to 257.9 +/- 68.3 ng/ml at 5 min after injection. PF4 antigen isolated from "postheparin plasma" by adsorption on heparin-agarose and elution with 2.0 M NaCl and "authentic PF4" isolated from human platelets showed identical patterns of migration as determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Material released by washed human platelets was injected intravenously into rats. The clearance of PF4 followed a biphasic exponential pattern. The half-lives (T1/2) for the fast and slow components for control rats were 1.2 and 17.1 min. Heparin significantly extended the half-life of human PF4 in rat circulation. The clearance of PF4 injected together with heparin followed a single component model with a half-life of 27.6 min. Administration of heparin to rats that had been previously injected with human platelet releasate resulted in a 30-fold increase of plasma PF4 level in their circulation. The clearance of PF4 from the circulation of these rats (T1/2 = 45 min) fitted a single component model. We propose that PF4 is originally secreted by platelets into circulation and subsequently bound reversibly to vascular sites from which it can be released back into the circulation by heparin. The fast component of PF4 clearance that is abolished by heparin may reflect binding of this protein to the endothelial cells.

An investigation into the validity and reliability of the marking of students' orthodontic practical work

This study has shown all three examiners to be different; surely a reflection of human nature. One examiner appeared to be strongly influenced by the students' past performance in the course, and the results confirm the findings of Natkin and Guild (1967) that examiners do not always observe the same errors and even when they do, may attach differing importance to the observed deficiency. It was found that an examiner's standard may vary from day to day but, in general, the intra- and inter-examiner correlations were similar to those reported in other studies of undergraduate practical work (Lilley et al., 1968; Silvestri et al., 1979; Goepferd and Kerber, 1980). It may be concluded that: 1. All marking should be done "blind' whenever possible. 2. Marking, once started, should be finished without a break as an examiner's own "pass' standard may vary unduly from one occasion to another. 3. The entire batch of material should be marked by the same examiner, as another could have a significantly different pass standard even though they might agree on the candidates' final order. 4. Because one examiner may subconsciously attach rather more importance to an aspect of the work that another does not notice, there would be a case for two or more examiners carrying out the marking. Their average marks could then be used. In this case, each examiner would, of course, mark the entire batch.

A comparative study of the old tuberculin tine test and the PPD-tine test

Forty-one children suspected of having tuberculosis were simultaneously given an intermediate strength Mantoux test, an old tuberculin tine test (OT), and a purified protein derivative (PPD) tine test. Each test was read at 48 hours, and the largest diameter of induration was recorded. Twenty-nine patients had a positive reaction to the Mantoux test, 20 patients had a positive reaction to the OT tine test, and 16 patients had a positive reaction to the PPD-tine test. There were seven instances of a doubtful reaction to the OT tine test and nine to the PPD-tine test. Two children with positive Mantoux tests had negative OT tine tests, and four with positive Mantoux tests had negative PPD-tine test reactions. There was a significant difference between the number of positive reactors to the Mantoux test and both tine tests. If all tine test reactions of 2 mm or more were considered positive (doubtful plus positive reactors), there was no significant difference between any of the tuberculin tests. All suggestively positive tine reactors should, therefore, be retested with a Mantoux test to avoid false-negative interpretation of the tines.

Identification and separation of secreted platelet proteins by isoelectric focusing. Evidence that low-affinity platelet factor 4 is converted to beta-thromboglobulin by limited proteolysis

Low-affinity platelet factor 4 and beta-thromboglobulin are low molecular weight platelet secretory proteins that have common antigenic determinants. Four amino acids (Asn-Leu-Ala-Lys) at the amino terminus of beta-thromboglobulin are deleted, but the remaining sequences of the two peptides appear to be identical. Low-affinity platelet factor 4 and beta-thromboglobulin have respective isoelectric points at pH 8.0 and at pH 7.0. Identification, quantitation, and separation of both proteins was achieved by a method combining preparative isoelectric focusing and specific radioimmunoassay with anti-low-affinity platelet factor 4 antibody. It has been determined that the supernate processes immediately after platelet aggregation induced by ionophore A23187 or thrombin contains approximately 80% low-affinity platelet factor 4, 8% beta-thromboglobulin, and 12% highly cationic immunoreactive material (platelet basic protein). Experimental evidence suggests that low-affinity platelet factor 4 is originally secreted by platelets and then converted to beta-thromboglobulin by a platelet-derived, heat-labile protease that is inhibited by phenylmethylsulfonyl fluoride.

Primary drug resistance in children. Drug susceptibility of strains of Mycobacterium tuberculosis isolated from children during the years 1973 through 1977 at the Kings County Hospital Center of Brooklyn

A continuing study of the frequency of primary drug resistance among children treated at the Kings County Hospital Center of Brooklyn during the years 1973 through 1977 showed a high incidence of primary drug resistance to isoniazid (8.8 per cent) and to streptomycin (12.3 per cent). In contrast, there were no strains resistant to cycloserine, viomycin, ethambutol, or rifampin, and only one of 57 strains (1.8 per cent) was resistant to ethionamide, and one (1.8 per cent) was resistant to para-aminosalicylic acid. Comparison with previous studies begun in 1961 showed no significant increase in resistance to isoniazid during 3 prior periods of study and no increase in resistance to streptomycin during the last 2 periods of study. It must be emphasized that these findings relate only to the children of a local community, and do not reflect the prevalence of primary drug resistance elsewhere in this country or among different age groups.

Heparin Induced Release of Low Affinity Platelet Factor Four

Heparin has been reported to effect platelet function. We studied the effect of commercial beef lung heparin on the release of a platelet specific protein, the low affinity platelet factor 4(LA-PF4) in vitro and vivo. LA-PF4 shares Common antigenic determinants with B thromboglobulin, LA-PF4 was measured in platelet poor plasma (PPP) by radioimmunoassay. The mean levels of LA-PF4 in PPP from citrated blood and citrated blood with added heparin (final concentration 1.5 unit/ml) were 78.3±18.3 and 242.5±117.1 ng/ml respectively. (Mean ± SD, p <0.01). Addition of heparin to blood collected in a mixture of E EDTA, prostaglandin El, and theophylline did not result in an increase in LA-PF4 in PPP. A single intravenous bolus of heparin was administered to two normal individuals and the levels of LA-PF4 measured before and at 15,30 and 180 minutes later. An increase in the levels of LA-PF4 in the PPP from a baseline of 66.7 and 30.2 ng/ml/106 platelets to 166.7 and 167.4 ng/ml/106 platelets respectively were noted in 30 minute sample. There was no increase in LA-PF4 at 15 minutes. At 180 minutes levels were at baseline. It is concluded that heparin stimulates release of LA-PF4 from platelets both in vitro and in vivo. LA-PF4 has antiheparin action and is being investigated as a marker for thrombosis. Its release by heparin may, therefore, have an important implication.

Increased Levels of Low Affinity Platelet Factor 4 in Plasma and Urine of Patients With Chronic Renal Failure

Low affinity platelet factor 4 (LA-PF4) is a specific platelet secretory protein immunologically related to β-thromboglobulin and to platelet basic protein that stimulates cell growth. The level of LA-PF4 antigen was determined by specific radioimmunoassay in platelet poor plasma (PPP) and platelet rich plasma (PRP) of 17 normal individuals (NI), 9 patients on hemodialysis (HD) and 18 patients with chronic renal failure (CRF) who were not dialysed. Eight patients with glomerular filtration rate (GFR) 5-20 ml/min were included to group 1 and 10 patients with GFR 30-50 ml/min were included to group 2. Levels of LA-PF4 in ng/ml PPP were 31.9 ± 2.8 in NI, 291.8 ± 26.3 in HD, 149.4 ± 45.2 in group 1 of CRF and 103.7 ± 11.1 in group 2 of CRF. Differences between patients and NI were significant at P <0.05. After 3 hours of hemodialysis LA-PF4 increased to 505.0 ± 92.3 (P < 0.05), however, there was no changes in PPP level across the artifical kidney at one hour. The levels of LA-PF4 in PRP of patients with CRF and HD did not differ from NI. Mean LA-PF4 excretion in urine (ng/day/100mg creatinine) was 57.7 ± 6.4 (range 33.3-75.7) in 6 NI with GFR >60 ml/min and 1461.5 ± 674.6 (range 105.3-7041.6) in 10 CRF patients. In conclusion, elevation of LA-PF4 in PPP of patients with CRF and its increased urinary excretion suggest stimulation of platelet secretion and/or decreased metabolism of LA-PF4 in the kidney.

Polymorphism of Platelet Secretory Proteins and Their Mitogenic Activity

Three low molecular weight proteins: β-thromboglobulin (βTG), low affinity plalelet factor 4 (LA-FF4) and platelet basic protein (PBP) have been purified from the material secreted by human platelets stimulated by lonophore A231S7. The preparative steps included heating at 100°C for 5 min, isoelectric focusing (pH gradient 3.5-10.9 in sucrose) and affinity chromatography on hepar in-agarose (elution with 0.4-0.5M NaCl). BTG, LA-PF4 and PBP showed complete immunological identity using anti-LA-PFi, antibody. Their respective isoelectric points were at pH 7.0, 8.0 and 10.9. Purity was confirmed by NH2 terminal amino acid analysis (βTG; gly; U1-PF4 asp; PBP: gly) and electrophoresis. At the NH2 terminal end LA-PF4, had four additional amino acids (Asn-Leu-Ala-Lys) while residues 5-21 of LA-PF4 and 1-16 of βTG were identical. As determined by Isoelectric focusing and specific radioimmunoassay the proportions of βTG, LA-PF4 and PBP released from platelets were 70%, 14% and 16%, respectively. Evidence is presented that LA-PF4 is a nrotein originally secreted by human platelets and converted to STG by a heat labile protease associated with the platelets. The three proteins Initiated DMA-synthesis in serum-arrested Swiss 3T3 cells in 0.4% serum. Activity of PBP was observed below 1 ng/ml and saturated at 50 ng/ml. LA-PP4 and βTG were 10 or 40 fold less active, respectively.

Surgical treatment of mandibular joint disorders

This paper deals with the operations available for disorders of the temporomandibular joint. It mentions the criteria and techniques for doing these operations, namely high condylectomy, augmentation, interposition grafts and rib grafts and reviews the results of a 15-year follow-up on 64% of 130 patients on whom the author has operated.