Clinical use of single-dose surfactant TA therapy for premature infants with severe respiratory distress syndrome

A single dose of surfactant TA was given as rescue therapy to four small premature infants with severe respiratory distress syndrome requiring mechanical ventilation. Birth weights ranged from 810 to 1200 gm. The dose of 100-120 mg/kg was given at the mean age of 5 hours, with range of 3 to 7 hours. Following surfactant therapy, there was a significant improvement (p < 0.05) in a/APO2 (raising from 0.11 +/- 0.05 before treatment to 0.34 +/- 0.19 at 6 hours after treatment). There was also a significant reduction in the severity of respiratory distress syndrome at 24 hours post-therapy. One baby died of sepsis at 40 hours of life; one survived without complications. The other two cases developed severe bronchopulmonary dysplasia later. We concluded that early use of exogenous surfactant is beneficial in small premature infants with severe respiratory distress syndrome.

Recurrent and acquired hepatitis C viral infection in liver transplant recipients

To examine the postliver transplant recurrence of hepatitis C virus (HCV) infection in patients with pretransplant infection, as well as its acquisition in patients without prior infection, we used the polymerase chain reaction to amplify HCV RNA in serum and/or liver samples of 89 patients with alcoholic and cryptogenic cirrhosis undergoing liver transplantation. Results were correlated with histologic findings from posttransplant liver biopsies. Ninety-five percent of patients with pretransplant infection had posttransplant viremia. In contrast, 35% of patients without pretransplant infection acquired the virus (P less than 0.0001). Pretransplant HCV infection predisposed patients to hepatitis in the new graft. HCV RNA was present in serum of 96% of patients with posttransplant hepatitis. Fifty-six percent of patients with posttransplant HCV infection had no evidence of liver damage at least 1 year posttransplant. However, of those patients with histologic hepatitis, chronic active hepatitis was common. It is concluded that although HCV infection recurs posttransplant in almost all infected patients, acquisition of the HCV infection with transplant is common. Pretransplant HCV infection is an independent risk factor for the development of posttransplant hepatitis. HCV infection accounts for the majority of posttransplant hepatitis not due to cytomegalovirus, and although many patients with posttransplant viremia have little evidence of histologic hepatitis, significant hepatic damage may occur.

In vitro calcium deposition by rachitic rat matrix vesicles: nucleoside triphosphate supported calcium deposition

The present study was designed to test whether ATP at serum levels can support matrix vesicle-mediated Ca deposition while the final Ca x P ion product is maintained at or below serum or cartilage fluid levels. Rachitic rat epiphyseal cartilage matrix vesicles (40 micrograms protein/ml) in a simple calcifying solution (without exogenously added Pi) containing 50 mM Tris, pH 7.6 at 37 degrees C, 0.1 M NaCl, 1.35 mM CaCl2, 1 mM ATP, deposited about 500 nmol Ca/mg protein after 5 h. The amount of Ca deposited increased with increases in incubation time, concentrations of ATP, Ca2+, hydroxide, and matrix vesicle protein. UTP, GTP, and CTP were equally effective in supporting Ca deposition by matrix vesicles. ATP-alpha,beta-methylene and ATP-beta,gamma-methylene were inhibitory for ATP-dependent Ca deposition. Experiments with limiting amounts of ATP and Ca2+ available in the calcifying solution indicated that ATP concentration at serum levels, in the presence of Ca x P ion products at serum or cartilage fluid levels, can support matrix vesicle-mediated Ca deposition.

Gastric bezoar caused by lecithin: an unusual complication of health faddism

We discovered an unusual bezoar in a previously healthy man who had been ingesting large amounts of a vegetable-derived oil touted to contain lecithin, which he purchased from health food stores in the belief that it had beneficial effects in lowering cholesterol levels and improving memory. The large intragastric mass, composed of fatty acids and lecithin, led to considerable morbidity, including abdominal pain, early satiety, and significant weight loss, and required surgical removal.

Comparison of normal and rachitic rat matrix vesicles

Accumulated information about MVs in PO4-deficient rachitic rats shows them to be normal in most aspects. Both normal and rachitic MVs show the same ultrastructural features and selective spatial distribution in the growth plate, and both contain a nearly identical array of major proteins. Rachitic and normal MVs show the same avidity to calcify in vivo and in vitro. A slightly greater specific activity of ALP in rachitic MVs may enhance their calcifiability. We conclude that rachitic rat MVs are essentially 'normal' and can be used as an adequate model to study the mechanism of biological calcification.

Conversion of N-(2-chloroethyl)-4-piperidinyl diphenylacetate (4-DAMP mustard) to an aziridinium ion and its interaction with muscarinic receptors in various tissues

A 2-chloroethylamine derivative [N-(2-chloroethyl)-4-piperidinyl diphenylacetate (4-DAMP mustard)] of the selective muscarinic antagonist N,N-dimethyl-4-piperidinyl diphenylacetate (4-DAMP) was synthesized, and its conversion to an aziridinium ion and interaction with muscarinic receptors was investigated. When dissolved in aqueous solution at pH 7.4 and 37 degrees, 4-DAMP mustard released an equivalent amount of chloride. The release of chloride was consistent with a first-order process having a half-time of 5.7 min. The aziridinium ion reached a peak concentration at 32 min, corresponding to 75% of the initial concentration of 4-DAMP mustard. When homogenates of rat brain, heart, and submaxillary gland were incubated with 4-DAMP mustard (9 nM) for 1 hr, washed extensively, and then assayed for muscarinic receptor binding properties, a 56% decrease in the binding capacity of N-[3H]methylscopolamine in the heart and brain and a 71% decrease in the gland were observed, without a significant change in the dissociation constants. The affinity of 4-DAMP mustard and its transformation products for muscarinic receptors was determined in competitive binding experiments with N-[3H] methylscopolamine, and the results show that the aziridinium ion of 4-DAMP mustard was the most potent form, compared with the parent 2-chloroethylamine (4-DAMP mustard) and the alcoholic hydrolysis product. The rates of receptor alkylation by 4-DAMP mustard were measured in the rat heart and gland. Virtually no alkylation (less than 1%) occurred in the heart at a 4-DAMP mustard concentration of 1.6 nM, after 30 min, whereas almost 50% alkylation was observed in the gland under the same conditions. Almost complete alkylation of receptors in the gland could be achieved at a 4-DAMP mustard concentration of 200 nM, after 1 hr. Treatment of the isolated rat ileum with 4-DAMP mustard caused an irreversible blockade of contractions elicited by the muscarinic agonist oxotremorine-M, and this blockade persisted after extensive washing. The results presented here show that 4-DAMP mustard forms an aziridinium ion that binds irreversibly to muscarinic receptors and exhibits selectivity for M3, compared with M2 muscarinic receptors.

Neoplasms and related proliferative lesions in control Sprague-Dawley rats from carcinogenicity studies. Historical data and diagnostic considerations

Historical data are presented for neoplasms and related proliferative lesions from 1,170 Sprague-Dawley rats that served as controls in 9 carcinogenicity (2 year) studies conducted in the Safety Evaluation Facility of Ciba-Geigy Corporation, Summit, New Jersey. The most common neoplasm was pituitary adenoma, which occurred in 62.2% of the male and 84.7% of the female rats. Incidences of other neoplasms that occurred in more than 6.0% of the rats were, for males, benign pheochromocytoma (19.0%), cutaneous keratoacanthoma (7.9%), pancreatic islet cell adenoma (7.5%), benign testicular interstitial cell tumor (6.5%), and thyroid C-cell adenoma (6.5%). For females these incidences were mammary fibroadenoma (31.3%), mammary adenocarcinoma (16.8%), and mammary adenoma (6.5%). Focal cortical hypertrophy/cystic degeneration of the adrenal, a focal nonneoplastic lesion of zona fasciculata cells that often degenerate into large cysts, was present in 23.4% of all male and 82.7% of all female rats. Criteria for the differential diagnoses of selected neoplasms and related lesions are presented.

Bone-inducing agent (BIA) from cultured human Saos-2 osteosarcoma cells

The Saos-2 line of human osteosarcoma cells was established in culture in 1975. These cells produce a large amount of alkaline phosphatase but little or no matrix in vitro, and are unable to grow when transplanted into athymic mice. We decided to test our local strain of Saos-2 cells for bone-inducing ability in the skeletal muscle of athymic mice by implanting freeze-dried, acetone-defatted cells, with and without a collagen carrier. A bone-inducing activity (BIA) thus was demonstrated in 88% of 90 implants of devitalized Saos-2 cells. In further studies, we have used guanidinium hydrochloride (Gu-HCl) to extract, solubilize, and remove the Saos bone-inducing agent(s) in an active state which when reprecipitated by aqueous dialysis was able to induce ultrastructurally typical endochondrial bone formation in nude mouse muscle in 92% of 48 implants. This preliminary report is offered to alert investigators to the presence of an extractable BIA in Saos-2 cells.

Antibodies to hepatitis C virus in low-risk blood donors: implications for counseling positive donors

The significance of antibodies to hepatitis C virus (HCV) found by screening enzyme-linked immunoassay testing in a low-risk blood donor population is unclear. The rate of false positivity in this group as well as the usefulness of supplemental testing were examined by correlating the results of two screening enzyme-linked immunoassays (Ortho Diagnostics, Raritan, NJ, and Abbott Laboratories, North Chicago, IL) with supplemental antibody testing by the recombinant immunoblot assays (1 and 2) (Ortho) and neutralization assay (Abbott). Polymerase chain reaction was used to detect HCV genomic RNA to confirm viremia. Among 11.243 volunteer donors who were screened for the presence of antibodies to HCV by enzyme-linked immunoassay, 60 (0.53%) sera were repeatedly reactive. Twenty-five of these 60 sera were available for further testing. Seven sera were reactive by both screening enzyme-linked immunoassays, as well as by both recombinant immunoblot and neutralization assays. Six of these seven sera had detectable HCV genomic RNA by polymerase chain reaction. Among the remaining 18 sera, none were reactive by either recombinant immunoblot assays, whereas two sera were reactive by the neutralization assay only. None of the 18 samples had detectable HCV genomic RNA. Five of the six sera with elevated aminotransferase levels were among the seven sera reactive by all immunoassays. It is concluded that there is a significant false positivity rate associated with screening enzyme-linked immunoassay testing in a low-risk blood donor population. Supplemental testing correlates well with detection of hepatitis C genomic material by polymerase chain reaction and identifies donors who are truly infected.

Failure to detect hepatitis C virus genome in human secretions with the polymerase chain reaction

Although hepatitis C infection has been clearly demonstrated to be transmitted through blood products or blood contamination, most cases of sporadic hepatitis C infection are unassociated with parenteral risk factors, and it is unclear how infection might be acquired by nonparenteral means. One potential mode of nonparenteral transmission is through body secretions. We used a highly sensitive and specific polymerase chain reaction assay to determine whether hepatitis C viral genomic RNA could be detected in secretions obtained from nineteen individuals with chronic hepatitis C virus infection. Although hepatitis C genomic RNA was found in all 19 sera, hepatitis C virus RNA was not detected in any samples of saliva, semen, urine, stool or vaginal secretions from these patients. Viral titers in serum ranged from 10(2) to 10(7) polymerase chain reaction units/ml. The sensitivity of our polymerase chain reaction assay indicates that, if hepatitis C virus were in secretions, it would be present in amounts less than 1 to 4 polymerase chain reaction units/ml. This contrasts with hepatitis B virus infection, in which serum titers frequently are in excess of 10(9) copies of hepatitis B genomes/ml. Body secretions have been found to contain up to 10(6) copies of hepatitis B genomes/ml. Our findings support seroepidemiological studies indicating that nonparenteral transmission of hepatitis C through secretions is uncommon and probably much less efficient than hepatitis B virus infection.

Delay of diagnosis of growth hormone deficiency in Taiwan

In view of the importance of early detection of growth hormone deficiency, the height and age at the first pediatric endocrinologic clinic visit of 45 patients with growth hormone (GH) deficiency between January 1988 to December 1989 were retrospectively analyzed. Twenty-three patients with idiopathic GH deficiency had a median age of 13 years (range, from 3.8 to 29.9 years) at their first visit and a median height standard deviation score (SDS) of -3.87 (-2.14 to -7.93). Nineteen children with hypothalamopituitary tumors at their first visit, at a median of 2.17 years (0.42 to 7.83 years) after diagnosis of the tumor, had a median height SDS of -3.15 (-0.58 to -4.70). Three children with GH deficiency secondary to cranial irradiation at their first visit, at 8.17 years (1.33 to 10 years) after treatment for their malignancy, had a height SDS of -3.15 (-2.13 to -3.72). It is well known that the earlier the replacement therapy is begun in such patients, the better the prognosis is for final adult height. Regular height measurement and routine screening for shortness at school entry may overcome this delay in diagnosis. In addition, patients who have received cranial irradiation or had hypothalamopituitary tumors should be regularly measured and studied if their height velocities become subnormal. Physicians dealing with children should keep the possibility of growth hormone deficiency in mind when examining a short child.

The partial sequencing of human nonspecific (bone/liver/kidney) alkaline phosphatase gene

1. A charon 4A human fetal liver genomic library was screened for human nonspecific alkaline phosphatase gene using the cloned human bone cDNA as a hybridization probe. 2. A clone 2.2 Kb DNA was sequenced and found to contain a piece of sequences encoding the 4-44th amino acids of NH2 terminus. 3. The other cloned 1.6 Kb DNA contains two segments of sequences each corresponding to two separate regions of the cDNA for alkaline phosphatase. The first segment of the DNA codes for the 83-141st amino acids whereas the second for 141-199th.

Rapid diagnosis of streptococcal pharyngitis with enzyme immunoassay

From June 1988 to May 1989, 444 throat swab specimens were tested with an enzyme immunoassay kit for rapid diagnosis of group A streptococcal pharyngitis. The results were compared with those of throat culture method. The rapid test was positive in 37 of 42 culture-positive specimens and negative in 379 of 402 culture-negative specimens, thus yielding a total agreement of 93.7%, sensitivity 88.1%, specificity 94.7%, positive predictive value 61.7%, negative predictive value 98.7%. According to this practical application, we suggest that enzyme immunoassay test can be applied in outpatient clinics by busy pediatricians for rapid diagnosis of group A streptococcal pharyngitis.

Matrix vesicle biogenesis in vitro by rachitic and normal rat chondrocytes

Calcifying matrix vesicles (MVs) are released from chondrocytes and osteoblasts in monolayer culture. In the present studies, we tested the ability of rachitic versus normal rat growth plate chondrocytes in micromass or monolayer primary cultures to produce MVs. Unlike earlier reports of in vitro MV biogenesis by chicken chondrocytes in which most MVs were released into the medium, we found that most of the released rat matrix vesicles were entrapped in a newly formed cartilaginous matrix enveloping the cells. These matrix-associated MVs could be isolated by mild collagenase treatment and concentrated by differential centrifugation. Vesicle production slowed in the older 2- to 4-week-old cultures and, unlike vesicle release from cultured chicken chondrocytes, active vesicle production did not show a second burst of activity at 3 to 4 weeks. Alkaline phosphatase (ALP) activity diminished with time in culture in cells and matrix vesicles, suggesting a decrease in differentiative expression. Protein profiles on SDS polyacrylamide gels of native matrix vesicles and culture-derived MVs from rachitic and normal cells were quite similar and showed a typical simplified protein pattern as compared to chondrocyte plasma membrane proteins. There were distinctive proteins migrating at 130, 80 to 95, 66, 43, 20, and 14 kd. Culture-derived MVs showed vigorous in vitro calcifying activity that was ALP related. We conclude that 1) rachitic chondrocytes are essentially normal in their matrix vesicle production; 2) matrix entrapment of MVs is a characteristic of rat chondrocyte cultures; and 3) culture-produced MVs are similar to native MVs in protein profile and calcifiability, and thus can be studied as a model for normal MV composition and calcification.

The isolation and partial sequencing of human bone alkaline phosphatase gene

1. A charon 4A human fetal liver genomic library was screened for human alkaline phosphatase sequences using the cloned human bone cDNA as a hybridization probe. 2. A positive clone was obtained and then characterized by restriction endonuclease cleavage analysis, hybridization experiments and partial DNA sequencing.

Purification and partial amino acid sequencing of alkaline phosphatase from rachitic rat epiphyseal cartilage

1. Alkaline phosphatase of rachitic epiphyseal cartilage was purified to apparent homogeneity by sequential application of monoclonal affinity, DEAE-cellulose, and Sepharose CL-6B chromatography. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the enzyme showed the presence of a dominant band corresponding to a molecular weight of 80,000. 2. The N-terminal amino acid sequence was determined as follows: Phe-Val-Pro-Glu-Lys5-Glu-Lys-Asp-Pro-Ser10-Tyr-Trp-Arg-Gln-+ ++Gln15-Ala-Gln-Glu- Thr-Leu20-Lys-Asn-Ala-Leu-Lys25-Leu-Gln-Lys-?-Asn-Val-Asn-?- Ala-Lys35-?-Ile-?- Met-Phe40-Leu-(Gly?)-Asp-(Ala/Gly?)-Met45-?-Val-?- (Val/Gly?).

Purification of bone alkaline phosphatase from human osteosarcoma

Purification of human bone alkaline phosphatase, derived from human osteosarcoma tissue, has been carried to electrophoretic homogeneity. The purification procedure involved three major steps: (1) chromatography on hydroxylapatite; (2) ion exchange chromatography; and (3) gel filtration. The resultant purified enzyme is a glycoprotein, has a molecular weight of approximately 80,000 (consistent with previous reports for the bone isoenzyme), and is characteristically inhibited by modest heat (56 degrees C, 30 min) and L-homoarginine but not by L-phenylalanine. The isolation and purification procedure described can lead to the production of significant amounts of highly purified bone alkaline phosphatase. Purified ALP can be used for an analysis of minor structural differences that appear to exist between the bone, liver and kidney isoenzymes. Such information could lead to the development of a clinical diagnostic procedure specifically for bone alkaline phosphatase.

Purification and partial amino acid sequencing of rat bone tumor (UMR106) alkaline phosphatase

Cultured rat osteosarcoma (UMR106) alkaline phosphatase was purified to apparent homogeneity by sequential application of polyclonal antibody affinity, DEAE-cellulose, and Sepharose CL-6B chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the enzyme preparation treated with sodium dodecyl sulfate and mercaptoethanol showed the presence of a dominant band (using silver staining) corresponding to a molecular weight of 80,000. The amino acid composition was similar to those of various alkaline phosphatases. The N-terminal amino acid sequence was determined as follows: Phe-Val-Pro-Glu-Lys-Glu-Lys- Asp-Pro-Ser-Tyr-Trp-Arg-Gln-Gln-Ala-Gln-Glu-Thr-Leu- Lys-Asn-Ala-Leu-Lys-?-Gln-Lys-?-Asn-Val-Asn-Ala-Lys.

Purification and partial amino acid sequencing of bovine kidney alkaline phosphatase

Bovine kidney alkaline phosphatase (ALPase) was purified by the sequential application of monoclonal anti-bovine cartilage ALPase affinity, DEAE-cellulose, and Sepharose CL-6B chromatography. Sodium dodecyl sulfate-polyacrylamide-gel electrophoresis showed the presence of a single band corresponding to a molecular weight of 80,000. The N-terminal amino acid sequence of bovine kidney alkaline phosphatase was determined as follows: Leu-Val-Pro-Glu-Lys-Asp-Pro-?-Tyr-Trp-Arg-Asp-Gln-Ala-Gln.

The deposition of calcium pyrophosphate by NTP pyrophosphohydrolase of matrix vesicles from fetal bovine epiphyseal cartilage

About 5 mumol CaPPi/mg protein was deposited within 3 h in the presence of the reaction mixtures containing 1 mM ATP, 2 mM Ca2+, 1 mM Pi, and 17 micrograms of purified NTP pyrophosphohydrolase. At 1 mM ATP, 50% of the deposition was inhibited by 0.5-1 mM of various substrate and product analogues including AMP, ADP, and ethylene hydroxyl diphosphonate. The magnitude of inhibition on NTP pyrophosphohydrolase activity was in the order of AMP = CMP = ADP greater than adenosine greater than adenine greater than NAD = NADP. AMP, CMP, ADP, and adenosine are competitive inhibitors. The modes of inhibition by adenine, NAD, and NADP differ from the competitive inhibition. Ribose, 3'-AMP, 2'-AMP, and cAMP did not inhibit the enzyme activity.

Development and cross-reactive properties of monoclonal antibodies to bovine matrix vesicle alkaline phosphatase

Alkaline phosphatase (ALPase), concentrated in the membranes of matrix vesicles, is believed to play a role in initial calcification. To further purify, characterize, and identify this enzyme in tissue, a monoclonal antibody was developed against the ALPase of isolated fetal calf matrix vesicles. Splenic lymphocytes derived from mice immunized with Sepharose 6B-purified fetal calf matrix vesicle ALPase were fused with mouse plasmacytoma cells (line X63-Ag-8.653) using standard hybridoma technology. Hyperimmune sera and hybridoma culture supernatants were screened for the presence of specific antibody using a newly developed double-immunosorbent assay in which putative antibody is added to microtiter plate wells precoated with affinity-purified rabbit antimouse immunoglobulin. After incubation and washing, partially purified fetal calf matrix vesicle ALPase is added to each well. The enzyme adheres only to wells that contain specific anti-ALPase antibody. These wells are identified by adding the enzyme substrate p-nitrophenyl phosphate and reading the wells in a plate-reading spectrophotometer at 405 nm. A hybridoma-producing specific antibody was subsequently cloned and grown as ascities-producing tumors in pristane-primed mice. Ouchterlony analysis indicated that the cell line secretes an immunoglobulin of IgG1 class. This antibody reacts specifically with ALPase derived from calf matrix vesicles and cross-reacts with ALPase of bovine kidney, liver, and placental origin and human bone but does not cross-react with bovine intestinal ALPase or ALPase derived from matrix vesicles isolated from rachitic rat growth plate cartilage.

Purification and partial characterization of alkaline phosphatase of matrix vesicles from fetal bovine epiphyseal cartilage. Purification by monoclonal antibody affinity chromatography

Alkaline phosphatase of matrix vesicles isolated from fetal bovine epiphyseal cartilage was purified to apparent homogeneity using monoclonal antibody affinity chromatography. The enzyme from the butanol extract of matrix vesicles bound specifically to the immobilized antibody-Sepharose in the presence of 2% Tween 20 whereas the major portion of nonspecific protein was removed by this single step. Of various agents tested, 0.6 M 2-amino-2-methyl-1-propanol, pH 10.2, was the most effective in eluting 80-100% of the enzyme initially applied. Both Tween 20 and 2-amino-2-methyl-1-propanol associated with the eluted enzyme were effectively removed by the sequential application of DEAE-cellulose and Sepharose CL-6B chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the enzyme preparation treated with sodium dodecyl sulfate and mercaptoethanol showed the presence of a dominant band (using silver staining) corresponding to a molecular weight of 81,000. This molecular weight was nearer reported values for rat liver (Ohkubo, A., Langerman, N., and Kaplan, M. M. (1974) J. Biol Chem. 249, 7174-7180) and porcine kidney (Cathala, G., Brunel, C., Chapplet-Tordo, D., and Lazdunski, M. (1975) J. Biol. Chem. 250, 6040-6045) alkaline phosphatase, than to previously reported values for chicken (Cyboron, G. W., and Wuthier, R. E. (1981) J. Biol. Chem. 256, 7262-7268) and fetal calf (Fortuna, R., Anderson, H. C., Carty, R. P., and Sajdera, S. W. (1980) Calcif. Tissue Int. 30, 217-225) cartilage matrix vesicle alkaline phosphatase. The purified alkaline phosphatase was activated by micromolar Mg2+. The amino acid composition of cartilage alkaline phosphatase was found to be similar to that previously described for porcine kidney (Wachsmuth, E. D., and Hiwada, K. (1974) Biochem. J. 141, 273-282). Double immunoprecipitation data indicated that monoclonal antibody against cartilage alkaline phosphatase cross-reacted with fetal bovine liver or kidney enzyme but failed to react with calf intestinal or rat cartilage enzyme. Thus these observations suggest that alkaline phosphatase of matrix vesicles from calcifying epiphyseal cartilage is a liver-kidney-bone isozyme.

The deposition of calcium pyrophosphate and phosphate by matrix vesicles isolated from fetal bovine epiphyseal cartilage

Since calcium (Ca) deposition by isolated fetal bovine matrix vesicles is selectively supported by nucleoside triphosphate, and since the Ca deposits appear to be amorphous by transmission electron microscopy, attempts were made to study further the nature of these Ca deposits. Calcification of isolated matrix vesicles was allowed to occur in a calcifying medium in which either inorganic phosphate (Pi) or [gamma-P]ATP was labeled with 32P. 32P in Ca P (pyrophosphate) deposits were analyzed by a Dowex 1 X 10 anion exchange chromatography. The results of the analysis indicate that the (32P) radioactivity was mainly associated with Pi when Pi in the calcifying media was labeled with 32P. In contrast, 32P was found to be associated with inorganic pyrophosphate (PPi) when [gamma-32P]ATP was used. Using a specific enzyme coupling assay for PPi, the presence of PPi in the Ca deposits was demonstrated. The amounts of Pi and PPi in the Ca deposits initiated by fetal calf matrix vesicles were found to be approximately equal. To exclude the possibility that the major part of PPi of Ca P deposit existed as adsorbed form, the deposition was performed under the conditions in which Pi was omitted from calcifying medium. The results of these experiments showed that substantial amount of PPi and Ca deposits remained the same and was not correlated to the amount of Pi in these deposits. In contrast, Pi of CaP was decreased if Pi was omitted from the calcifying medium. Thus, it appears that the major portion of PPi exists as mineral rather than adsorbed form.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation of a plasma membrane-enriched fraction from collagenase-suspended rachitic rat growth plate chondrocytes

An attempt was made to concentrate plasma membranes of homogenized chondrocytes isolated by collagenase digestion of rachitic rat epiphyseal growth plate cartilage. This study reports the characterization of enzymes in the plasma membrane of isolated chondrocytes and their comparison with extracellular matrix vesicle components. The plasma membrane-enriched fractions that were obtained showed a sevenfold increase in 5'-nucleotidase and a 15-fold increase in alkaline phosphatase, both of which are regarded as plasma membrane markers. SDS-polyacrylamide gel electrophoretic profiles of proteins extracted from membrane fractions contained several major protein bands also seen in isolated matrix vesicles. These studies indicate the usefulness of concentrating plasma membrane components from isolated chondrocytes, after the chondrocytes have been enzymatically freed from investing matrix and other stromal components by collagenase.

Electron microscopic localization of adenosine triphosphate (ATP)-hydrolyzing activity in isolated matrix vesicles and reconstituted vesicles from calf cartilage

The presence and distribution of adenosine triphosphatase (ATPase) activity in isolated matrix vesicles and reconstituted vesicles from fetal calf epiphyseal growth plate cartilage was studied by electron microscopic cytochemical methods to determine whether phosphatase activity would be found concentrated on the inside or the outside of matrix vesicle membranes or on both sides, and whether reconstitution of vesicles from deoxycholate-solubilized substituents would lead to the reassembly of membranes with ATPase incorporated. ATPase activity was observed on both the outer and inner surfaces of the investing membranes of isolated matrix vesicles and reconstituted vesicles. A transmembrane location of ATPase could indicate phosphate transfer across the vesicle membrane. Orthophosphate released by phosphatase activity within the protected microenvironment of the matrix vesicle could combine with membrane- or lipid-bound calcium, known to be present in vesicles, to form the first hydroxyapatite mineral during calcification.

Purification and partial characterization of ATP pyrophosphohydrolase from fetal bovine epiphyseal cartilage

ATP pyrophosphohydrolase was partially purified from fetal bovine epiphyseal cartilage. The purification was about 10- and 100-fold over the enzyme activities of matrix vesicle fraction and cell homogenate, respectively. The pyrophosphohydrolase and alkaline phosphatase were separated by a sequential application of Sepharose CL-6B and DEAE-cellulose column chromatographies. The purified enzyme migrated as a single band corresponding to the molecular weight of 230,000 in sodium dodecyl sulfate-polyacrylamide disc gel by electrophoresis. The enzyme absolutely required Zn2+ for its activity and appeared to bind Zn2+ strongly with an apparent affinity of p[Zn2+]0.5 = 13.4. The apparent Km for ATP was 0.18 mM. The enzyme was also reactive toward various nucleoside triphosphates including GTP, CTP, and UTP. In contrast, various phosphodiesters including RNA, UDP-glucose, NAD, and bis-p-nitrophenylphosphate were 5% or less as reactive as the nucleoside triphosphates. The pyrophosphohydrolase was inactive toward adenosine 3':5'-monophosphate or various phosphonates. UDP-glucose (1 mM), NAD (1 mM), or RNA (1 mg/ml) failed to inhibit the ATP pyrophosphohydrolase activity. These observations suggest that the ATP pyrophosphohydrolase of the cartilage is probably not a phosphodiesterase I. The matrix vesicle fraction, which probably also included some plasma membrane vesiculated during collagenase digestion, contained the highest specific activity of the enzyme as compared to other subcellular fractions of either epiphyseal or articular cartilage.

Calcification of isolated matrix vesicles and reconstituted vesicles from fetal bovine cartilage

Ca deposition by isolated matrix vesicles from fetal calf growth plate cartilage and by a deoxycholate extract from matrix vesicles that included their phosphatase was studied under defined in vitro conditions. Electron microscopy showed that after removal of deoxycholate and lyophilization of the vesicle extract, new vesicles were reconstituted, often with multiple membrane layers. Both intact calf vesicles and reconstituted vesicles initiated Ca deposition maximally when supplied with ATP, GTP, CTP, or UTP. Only nucleoside triphosphates supported Ca deposition well; mono- and diphosphoesters, although hydrolyzed, were ineffective as substrates. Nucleoside triphosphates supported Ca deposition even if the final [Ca] X [P] reached in the reaction mixture was below a metastable level (3.5 mM2), suggesting that matrix vesicles or reconstituted vesicles promote calcification by localizing Ca or PO4 or both. ATP or GTP supported Ca deposition readily at concentrations ranging from 0.25 to 1.0 mM but, at 2.5 and 5.0 mM, Ca deposition was inhibited. The ATPase of intact matrix vesicles and reconstituted vesicles was stimulated by addition of Ca2+ and Mg2+. Ca deposition did not require additional Mg2+. These results lend support to the hypothesis that matrix vesicles and their phosphatases play an important role in mineralization.

A simple and defined method to study calcification by isolated matrix vesicles. Effect of ATP and vesicle phosphatase

A simplified and defined system was developed to study in vitro calcium phosphate deposition by isolated matrix vesicles from rabbit growth plate cartilage, and to examine the relationship between vesicle phosphatase and calcium deposition. Samples of suspended vesicles containing 25 microgram of protein, were incubated for 2 h in a 45Ca-labelled solution with 2.2 mM Ca2+, 1.6 mM PO 3/4-and 1 mM ATP at pH 7.6. Calcium deposition was related to the amount of PO4 hydrolysed by matrix vesicle phosphatases from ATP and other phosphate esters. Ca2+ or Mg2+ was found to stimulate matrix vesicle ATPase, but the hydrolysis of phosphoenolpyruvate, glucose 1-phosphate, beta-glycerol phosphate and AMP was independent of either cation. All of the above substrates supported calcium deposition. 1 mM ATP was more effective than 5 mM in supporting calcium deposition, indicating inhibition of mineralization at higher ATP concentrations. Our results suggest that, in addition to concentrating calcium, vesicles provide phosphate from ATP for mineral formation and at the same time remove the inhibitory effect of ATP upon mineral deposition.

Specific adenosine binding proteins from rat liver

Specific adenosine-binding proteins from homogenates of rat liver have been fractionated on a DEAE-cellulose column. Three major peaks have been identified with respect to histone phosphokinase and cAMP and adenosine-binding activities. Peak I contains only histone phosphokinase activity not stimulated by cAMP. Peak II contains histone phosphokinase slightly stimulated by cAMP. Both cAMP- and adenosine-binding activities are found in this fraction. The major adenosine-binding protein is associated with Peak III. Histone phosphokinase in Peak III which also binds cAMP is stimulated 2-fold by 2.5 muM cAMP whereas adenosine at 2.5 X 10(-4)M inhibits these enzymes equally well in each of three peaks. The specificity of adenosine binding is discussed.