The contractile behaviour of EGTA- and detergent-treated heart muscle

Tension responses of rat ventricular trabeculae subjected to successive 'treatment' with EGTA and Triton X-100 are described in order to investigate the effects of chemical 'skinning' techniques. In some preparations the alkaloid saponin was also used before Triton. Ultrastructural evidence is cited that the 'EGTA-treatment' fails to render cells 'hyperpermeable', i.e. freely permeable to small ions, whereas both saponin and Triton do so. In this paper we show that contractile responses like those described previously for the 'EGTA-treated' tissue can be obtained. However, more detailed examination shows that such behaviour is quantitatively distinct from that of conventionally skinned fibres in a way that is incompatible with the notion of 'hyperpermeability'. The Ca-sensitivity after treatment with either EGTA, saponin or Triton is identical in our hands. However, this is not explained by free access of Ca (and EGTA) to the intracellular space in the EGTA-treated preparation: contractures develop with very different time courses, being fastest after Triton and only marginally slower when first exposed to saponin but a factor of five times slower after 'EGTA-treatment' alone. This applies to contractures evoked direct from Ca2+ concentration congruent to 10(-9) M to the test Ca2+ concentration at constant total buffer concentration. 'EGTA-treated' fibres develop tension when ATP or creatine phosphate (CrP) are removed from the bath. However, responses to ADP and to CrP changes persist with millimolar levels of ATP present, quite unlike the Triton-skinned muscle. Exposure to each of a variety of solutions for 24 h produce preparations showing similar behaviour: whatever the explanation for the EGTA-'skinning' phenomenon it is not dependent upon low bathing Ca2+ concentration. On the basis of the functional characteristics described here, and the structural results cited, we conclude that the cell membrane continues to function as a selective permeability barrier after 'EGTA-treatment': this treatment does not produce a model of a selectively 'skinned' cardiac cell.

The relationship between intracellular calcium and contraction in calcium-overloaded ferret papillary muscles

The photoprotein aequorin was microinjected into cells on the surface of ferret papillary muscles. Tension and aequorin light, a function of intracellular Ca concentration ([Ca2+]i), were monitored. The preparations were exposed to increased concentrations of extracellular Ca ([Ca2+]o). Small increases in [Ca2+]o led to the usual increase in both the systolic light signal and the developed tension. However, high [Ca2+]o led to a fall in developed tension known as Ca overload. This fall of tension was seen at lower [Ca2+]o if the experiment was performed in the presence of strophanthidin. In conditions of Ca overload, the systolic light signal was either similar in amplitude or larger than the systolic light observed under conditions which did not lead to Ca overload. Oscillations of diastolic light were invariably present under conditions of Ca overload. These oscillations were accompanied by after-contractions which were small in relation to the magnitude of the aequorin light oscillations. During Ca overload, the variance of the amplitude of the systolic light signal was greater than could be accounted for by the random nature of the arrival of photons. Small systolic light signals occurred when there had been an oscillation of light in the diastolic period immediately preceding the systolic light signal. Large systolic light signals occurred when the preceding period (approximately 1 s) was free of oscillations of light. These observations suggest that if the sarcoplasmic reticulum (s.r.) has spontaneously released its contents of Ca as shown by a diastolic [Ca2+]i oscillation, then a stimulated systolic Ca signal occurring within about the next second is smaller, possibly because it takes longer than this period for the s.r. to reload with Ca. If this process occurs randomly in the various cells of the preparation, developed tension will be reduced because those cells which have a small Ca release will act as a compliance in series with cells which have a large Ca release.

Potentiometric measurements of stoichiometric and apparent affinity constants of EGTA for protons and divalent ions including calcium

The stoichiometric affinity constants of H+, Ca2+, Mg2+ and Sr+ for the ligand EGTA were determined using a modified version of the pH metric method developed by Moisescu and Pusch (Moisescu, D.G. and Pusch, H. (1975) Pfluegers Arch. 355, 243). The values obtained were slightly higher than those previously published. In addition, the shift in the H+ and Ca2+ stoichiometric constants with ionic strength was found to fit an empirical relationship if the total ionic content of the titration solutions was measured in terms of ionic equivalents, Ie (Johansson, L. (1975) Acta Chem. Scand. A29, 365-373), rather than the formal ionic strength, If. Finally, the apparent affinity of EGTA for Ca2+ ions was measured using an abbreviated form of the titration technique. The measured apparent affinity constant agreed with published results only if calculated with respect to pH (measured) of 7.0, rather than pH (concentration).

Insulin-like growth factor II binding to cultured human chondrosarcoma cells

Cultured cells originally derived from a human chondrosarcoma (A1684) were used to investigate somatomedin binding in terms of kinetics and specificity. In this study, the rat somatomedin, multiplication-stimulation activity (MSA) was utilized. While the human chondrosarcoma cells did not exhibit a mitogenic response to MSA, the rate of transport of glucose and amino acids was significantly increased. In competitive binding experiments a specific insulin-insensitive MSA receptor was identified which showed half maximal displacement of tracer at a concentration of 250 ng/ml of MSA using whole cells. This receptor had an affinity constant of 4.8 X 10(7) M-1. Kinetic analysis of MSA binding to membrane preparations and to Triton X-100 solubilized membranes revealed an increase in the binding affinity to 1.28 X 10(8) M-1 and 2.8 X 10(8) M-1, respectively. Of particular significance is the observation that these cells have especially high levels of MSA receptors. Determination of binding capacity revealed that these cells contain approximately 1.9 X 10(6) MSA receptors per cell and therefore are an excellent model system for the characterization and purification of somatomedin receptors. Affinity labeling of the MSA receptor using the chemical crosslinking reagent, disuccinimidyl suberate, confirmed that this receptor was of the type II class of somatomedin receptors and exhibited a molecular weight of 218,000 under nonreducing conditions.

Comparative risks and costs of male and female sterilization

Couples who are considering elective sterilization should compare the risks and costs of male and female sterilization procedures as part of the decision process. Morbidity, mortality, failure rates, and short-term costs associated with male and female sterilization procedures were estimated from data available in previous case series. Male sterilization procedures were found to have zero attributable deaths and significantly less major complications when compared to female sterilization procedures. No less than 14 deaths a year can be attributed to female sterilization procedures in the US. Male and female sterilization procedures have efficacy rates that are not significantly different from each other. The short-term costs of female sterilization are 3.0 to 4.1 times that of vasectomy.

Influenza A virus nucleoprotein is a major target antigen for cross-reactive anti-influenza A virus cytotoxic T lymphocytes

Influenza A virus-specific cytotoxic T lymphocytes (CTL) capable of lysing cells infected with any influenza A virus ("cross-reactive CTL") constitute a major portion of the host CTL response to influenza. The viral nucleoprotein (NP), a major internal virion structural protein, has been implicated as a possible target antigen for cross-reactive CTL. To directly examine CTL recognition of NP, a vaccinia virus recombinant containing a DNA copy of an influenza A virus NP gene was constructed. We found that murine cells infected with this virus were efficiently lysed in a major histocompatibility complex-restricted manner by cross-reactive CTL populations obtained by immunization with a variety of influenza A virus subtypes. In addition, the recombinant vaccinia virus containing the PR8 NP gene was able to both stimulate and prime for a vigorous secondary cross-reactive CTL response. Significantly, splenocytes from mice primed by inoculation with the recombinant vaccinia virus containing the PR8 NP gene could be stimulated by influenza A viruses of all three major human subtypes. Finally, unlabeled target competition experiments suggest that NP is a major, but not the sole, viral target antigen recognized by cross-reactive CTL.

Selectivity in mobilisation of stored fatty acids by maturing cod, Gadus morrhua L

Lipids, proteins and carbohydrates diminish in the liver and muscle of cod when (a) food is inadequate or (b) the gonads are maturing. The results reported in this paper appear to show that the mobilisation of the lipids differs according to whether the need is just for energy (simple starvation) or for building up gonads. Two groups of fish from the same catch were starved. In one, the gonads were developing, while in the other the gonads had been surgically removed. Significantly more of the fatty acid C22:6 was mobilised from the liver lipids in the group with developing gonads, this fatty acid being present in the greatest amount in the gonads of either sex. The fatty acid C18:1 is also important in the gonads, and this was also preferentially removed from all the livers of maturing-starving fish when compared with gonadectomised-starving, though here the effect was not statistically significant. Some discrimination therefore appears to be exercised when hepatic lipids are removed for gonad development. No selectivity was observed in the mobilisation of fatty acids from the muscle.

Acute airway obstruction following tooth extraction in hereditary angioedema

Life threatening airway obstruction occurred following a single tooth extraction in a patient who had hereditary angioedema, despite preoperative administration of FFP and danazol. Emergency intubation was performed in the operating room, and assisted respiration was required during the acute attack. The clinician should be aware that an acute attack of HAE may occur even though recommended medical management regimens are followed and should be prepared for emergency airway control.

Recombinant vaccinia virus primes and stimulates influenza haemagglutinin-specific cytotoxic T cells

The ability of vaccinia virus to accept and express cloned genes encoding immunologically important proteins of unrelated viruses and malarial parasites has suggested a novel approach to the development of live vaccines. Vaccinia virus recombinants retain infectivity and stimulate synthesis of specific antibodies to the cloned gene products in vaccinated animals. Moreover, animals inoculated with recombinants expressing the influenza virus haemagglutinin (HA), the hepatitis B virus surface antigen, and type 1 herpesvirus glycoprotein D were protected against subsequent challenge with the corresponding virus. For maximal effectiveness, vaccines should produce cellular as well as humoral immunity. We now report that a vaccinia virus recombinant, expressing the influenza HA, primes and stimulates a specific murine cytotoxic T-lymphocyte (CTL) response. Histocompatible cells infected with this recombinant also serve as targets for CTLs. These properties make vaccinia virus a unique tool for studying cell-mediated immunity and enhance the attractiveness of this vector for production of live vaccines.

Live recombinant vaccinia virus protects chimpanzees against hepatitis B

Hepatitis B virus (HBV) is an important human pathogen responsible for over 200 million cases of chronic infection, many of which progress to hepatocellular carcinoma. Although HBV cannot be propagated in tissue culture, highly effective subunit vaccines obtained from the plasma of chronically infected patients have been developed and licensed. Such vaccines are safe but their expense and limited quantities make them unavailable to most Third World countries. Other approaches to vaccine construction, including purification of the HBV surface antigen (HBsAg) from genetically engineered eukaryotic cells and the synthesis of peptides predicted from the nucleotide sequence of the HBsAg gene, are still under evaluation. Another potential application of recombinant DNA technology to vaccine development is the use of live virus vectors to express foreign genes. An infectious vaccinia virus recombinant that expressed the HBsAg in animal cells and which stimulated the production of antibody to HBsAg (anti-HBs) in rabbits represented a novel candidate vaccine of this class. As a continuation of our earlier study, we now present evidence that chimpanzees vaccinated with a live recombinant vaccinia virus protected against hepatitis following challenge with HBV.

Plasmodium knowlesi sporozoite antigen: expression by infectious recombinant vaccinia virus

The gene coding for the circumsporozoite antigen of the malaria parasite Plasmodium knowlesi was inserted into the vaccinia virus genome under the control of a defined vaccinia virus promoter. Cells infected with the recombinant virus synthesized polypeptides of 53,000 to 56,000 daltons that reacted with monoclonal antibody against the repeating epitope of the malaria protein. Furthermore, rabbits vaccinated with the recombinant virus produced antibodies that bound specifically to sporozoites. These data provide evidence for expression of a cloned malaria gene in mammalian cells and illustrate the potential of vaccinia virus recombinants as live malaria vaccines.

General method for production and selection of infectious vaccinia virus recombinants expressing foreign genes

The production and selection of infectious vaccinia virus recombinants expressing foreign genes was facilitated by the construction of plasmid vectors. These vectors contain all or part of the vaccinia virus thymidine kinase (TK) gene interrupted by multiple unique restriction endonuclease sites placed adjacent to the TK promoter or another promoter translocated within the TK gene. The insertion of a continuous coding sequence for a foreign protein at one of the unique restriction endonuclease sites juxtaposes the transcriptional start site of a vaccinia promoter and the translational start site of a foreign gene. After transfection of vaccinia virus-infected cells with such plasmids, homologous recombination occurs between the vaccinia virus sequences flanking the chimeric gene and the same sequences within the virus genome. Recombinants formed in this manner have the chimeric gene inserted within the body of the vaccinia virus TK gene under control of a vaccinia virus promoter. Since recombinants have an interrupted TK gene, they are selected on the basis of their TK- phenotype and then checked for the presence and expression of the foreign gene. Infectious recombinant viruses expressing the procaryotic enzyme chloramphenicol acetyltransferase were constructed to optimize the system. The absence of chloramphenicol acetyltransferase activity in uninfected cells or in cells infected with wild-type vaccinia virus and the availability of a sensitive and quantitative enzyme assay allowed an estimation of the relative strengths of various promoter constructs. The expression of chloramphenicol acetyltransferase was detected within 1 h after infection of cells with recombinant virus, reflecting the early nature of the promoters used.

Reductions in coronary flow under resting conditions in collateral-dependent myocardium of patients with complete occlusion of the left anterior descending coronary artery

Flow per unit weight in collateral-dependent myocardium was quantified selectively in seven patients with complete occlusion of the proximal left anterior descending artery and prominent distal collateralization from the right coronary artery by infusing dissolved hydrogen into the right coronary artery for 10 to 15 minutes and monitoring hydrogen desaturation in the great cardiac vein. Coronary flow per unit weight in all myocardium draining into the great cardiac vein was quantified simultaneously by having the patient breathe helium and by monitoring arterial and great cardiac vein helium desaturation. Flow per unit weight in collateral-dependent myocardium averaged 38 +/- 8 (standard deviation) ml/min per 100 g and was in each case below the 95% confidence limit for normal individuals with the same rate-pressure product. Flow per unit weight in all myocardium draining into the great cardiac vein was systematically higher (51 +/- 8 ml/min per 100 g); because arteries other than the anterior descending had no stenoses greater than 30% in diameter, these values presumably reflect mixtures of subnormally perfused collateralized myocardium and adjacent normally perfused tissue. The findings suggest that coronary flow per unit weight is not maintained at usual basal values in densely collaterlized myocardium that is entirely collateral-dependent. The reductions in flow are presumably associated with marked reductions in local arterial pressure and raise the possibility of a chronic reduction in local myocardial metabolic demand.

Somatomedin carrier proteins

The somatomedins, such as the insulin-like growth factors I and II, somatomedins A and C, and multiplication-stimulating activity, are small, growth hormone dependent polypeptides which are the assumed mediators of growth hormone action on extraskeletal tissues. The somatomedins are unique among polypeptide hormones in that they exist in serum as two high molecular weight complexes of approximately 150 000 and 60 000 molecular weight. Little, if any, free hormone is present in plasma or serum. These circulating complexes appear to represent the reservoir for these hormones since none is stored in any other tissue and the circulating concentration (approx. 1 microgram/ml) exceeds the biologically active concentration of the free hormone by many fold. Many recent investigations regarding the subunit composition of the two serum carrier protein complexes and their effect on the biological activity of the somatomedins have revealed an elaborate system of intense physiological control ultimately aimed at delivering somatomedin to its specific receptor on the surface of the target cell.

EGTA purity and the buffering of calcium ions in physiological solutions

Results are presented for the purity of three commercial brands of the Ca chelator EGTA [ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid] as determined with pH-metric and oxalate precipitation methods and other techniques. The effect that the observed degree of hydration (2-4%) has on calculated values for [Ca2+] in Ca-EGTA solutions is described with reference to a theoretical dose-response relationship. In addition to the corrections for purity, the adjustments necessary to allow for ionic strength and the correction of pH readings to yield true [H+] activity or concentration values are described. These several corrections result in both a shift and a shape change for the dose-response curve compared with the curve calculated without these corrective procedures. Some authors have already taken some of these aspects into account, but this has not generally been made clear in the literature heretofore. The points raised may help to account for the wide variation of reported [Ca2+] ranges for Ca-sensitive cellular processes.

Construction and characterization of an infectious vaccinia virus recombinant that expresses the influenza hemagglutinin gene and induces resistance to influenza virus infection in hamsters

A DNA copy of the influenza virus hemagglutinin gene, derived from influenza virus A/Jap/305/57 (H2N2) was inserted into the genome of vaccinia virus under the control of an early vaccinia virus promoter. Tissue culture cells infected with the purified recombinant virus synthesized influenza hemagglutinin, which was glycosylated and transported to the cell surface where it could be cleaved with trypsin into HA1 and HA2 subunits. Rabbits and hamsters inoculated intradermally with recombinant virus produced circulating antibodies that inhibited hemagglutination by influenza virus. Furthermore, vaccinated hamsters achieved levels of antibody similar to those obtained upon primary infection with influenza virus and were protected against respiratory infection with the A/Jap/305/57 influenza virus.

Infectious poxvirus vectors have capacity for at least 25 000 base pairs of foreign DNA

To test the capacity of poxviruses for added foreign DNA, a recombinant was constructed that contains 24 700 bp of bacteriophage lambda DNA inserted within the vaccinia virus thymidine kinase (TK) gene. The recombinant is stable, infectious and replicates in tissue culture at the same rate and to the same titer as standard vaccinia virus. This size flexibility of the poxvirus genome and the lack of stringent packaging requirements are useful features for an infectious eukaryotic cloning vector.

Infectious vaccinia virus recombinants that express hepatitis B virus surface antigen

Potential live vaccines against hepatitis B virus have been produced. The coding sequence for hepatitis B virus surface antigen (HBsAg) has been inserted into the vaccinia virus genome under control of vaccinia virus early promoters. Cells infected with these vaccinia virus recombinants synthesize and excrete HBsAg and vaccinated rabbits rapidly produce antibodies to HBsAg.

Two methods for determining erucic acid in edible fats and oils: results from a collaborative study on a rapid, open-tubular (capillary) GLC method and comparison with an isolation TLC procedure

The results of an international collaborative study for the determination of 5% erucic acid in four samples of edible fats and oils with differing levels of 22:1 isomers other than erucic acid, based on the use of wall-coated (SILAR-5CP) open-tubular gas-liquid chromatography, are examined. The same samples had been analyzed in a separate collaborative study by an alternative and more complex method based on argentation thin-layer chromatography. Both methods rejected about the same proportion of participating laboratories and a few individual results from otherwise acceptable laboratories. The means and repeatabilities of the two methods were similar, but the gas-liquid chromatographic method showed better reproducibility.

Vaccinia virus: a selectable eukaryotic cloning and expression vector

Foreign DNA was inserted into two nonessential regions of the vaccinia virus genome by homologous recombination in cells infected with virus and transfected with plasmids containing the foreign DNA elements flanked by vaccinia virus DNA. Thymidine kinase-negative (TK-) recombinants were selected after inserting foreign DNA into the coding region of the TK gene of wild-type vaccinia virus; TK+ recombinants were selected after inserting the herpesvirus TK gene into TK- mutants of vaccinia virus. For TK+ expression, it was necessary to insert a 275-base-pair DNA fragment containing the initiation site and sequences upstream of an early vaccinia virus transcript next to the coding sequences of the herpesvirus gene. The unique ability of the herpesvirus TK to phosphorylate 125I-labeled deoxycytidine provided independent confirmation of gene expression. These studies demonstrate the use of vaccinia virus as a selectable cloning and expression vector, confirm the map location of the vaccinia virus TK gene, and provide initial information regarding the location of vaccinia virus transcriptional regulatory sequences.

Breast reconstruction in the burned adolescent female (an 11-year, 157 patient experience)

The experience accumulated after reconstruction of 157 burned breast patients has led to the development of surgical principles and techniques tailored to this problem. Most important among these principles is that the surgeon recognize and preserve viable breast bud tissue in the debridement phase of the acute burn. Reconstruction should begin when the burned breast envelope is insufficient and restricts normal growth. Best results are obtained if contracture release is complete, if defects are covered by thick split-thickness skin grafts, and if nipple-areola reconstruction is obtained from a normal opposite breast if present. Postoperative management should continue until wounds are mature and should include techniques to prevent contracture recurrence.

Methods for preventing pseudomonas folliculitis

This outbreak highlights a number of significant factors related to most pseudomonas folliculitis outbreaks. The bath water had not been changed in more than four weeks which led to a build-up of high levels of organic carbon. There was an extended interval of six days between subsequent OTD chlorine residual tests, allowing the chlorine residual to decrease to low levels between tests. It should also be noted that the OTD test, by design, measures both the active free chlorine and the inactive combined chlorine residual. Therefore OTD residual readings in the low normal range may actually represent below normal free active chlorine residual levels. The following measures are suggested to reduce the growth of pseudomonads in hot tubs and whirlpool baths and to prevent subsequent cases of pseudomonas folliculitis: 1. The OTD chlorine residual should be checked every day. The residual should be well above the minimum level suggested for the bath. Or, preferably, an automatic chlorinator should be installed. This device measures the free chlorine residual and automatically adds chlorine to keep the residual in the desired range. 2. The water in the bath should be changed at least every eight weeks in order to reduce the total organic carbon level. The water should be changed more frequently if the bath is used by a large number of persons. 3. If an outbreak of pseudomonas folliculitis is associated with a bath, the water should be changed and the bath washed with a chlorine-based solution. Also, the method of keeping the chlorine residual in the operating range should be re-evaluated.

Reinsertability after breast prosthesis pocket infection: an experimental study

We report the development of an animal model for the study of S. aureus infection in silicone gel-filled prosthesis pockets. The purpose of this study was to determine (1) whether successful reinsertion of a prosthesis into a contaminated pocket requires a finite recovery period between implant removal and reinsertion, and (2) whether parenteral antibiotic treatment affects the success of reinsertion. All infected pockets were lavaged with saline and none were drained, either after wound closure or after implant reinsertion. The results indicate that a delay of 2 or more hours between lavage and reinsertion protects against implant exposure. Therapeutic parenteral antibiotic treatment neither prevented implant exposure nor altered the effect of temporal delay on reinsertion. These studies coupled with recent clinical reports suggest that women who develop breast pocket infection need not wait months for restoration of breast symmetry.

Ecgonine methyl ester, a major metabolite of cocaine

Most assays for the identification of cocaine use are aimed at detection of benzoylecgonine, a major urinary metabolite. Gas chromatography assays require derivatization of benzoylecgonine. Recently, ecgonine methyl ester (methylecgonine) has been shown to be major urinary metabolite of cocaine in man after oral administration. These results indicate that ecgonine methyl ester is a prominent urinary metabolite after street use of cocaine, which primarily involves intranasal application and intravenous injection rather than ingestion. Advantages of GC/MS analysis for ecgonine methyl ester in identifying cocaine use include the ability to chromatograph it on common stationary phases without derivatization and its early elution.

Changes in bone and serum minerals after parathyroidectomy and their prevention by portacaval shunt

The effect of portacaval shunt and parathyroidectomy on the concentration of calcium, magnesium, phosphate and hydroxyproline in the bone and the concentration of the three minerals in the serum has been studied in the growing rat. Parathyroidectomy produced a decreased net bone reabsorption as evidenced by higher concentrations of calcium, magnesium and phosphate; and a reduced net matrix formation, as evidenced by lower concentrations of hydroxyproline. Portacaval shunt, when performed with parathyroidectomy, prevented the development of these changes and produced "normal" concentrations of most of those elements, comparable to their concentrations in the control animals. The changes in serum calcium and magnesium produced by parathyroidectomy were prevented when portacaval shunt was performed in conjunction with the former procedure. Portacaval shunt alone produced no significant changes except for hypophosphatemia. This hypophosphatemia is speculated to have stimulated the production of 1,25-(OH)2D3 in the kidney, which in turn produced those observed effects of portacaval shunt in the parathyroidectomized rat.

Long-term survival after coronary bypass surgery. Comparison of various subsets of patients with general population

Life-table analysis consecutive cases of isolated coronary bypass surgery at the Buffalo Hospital between 1973 and 1977 showed an estimated survival of 94 per cent at five years, equal to that of an age- and sex-matched group of the US population. Subsets of these patients divided according to sex, age, number of vessels narrowed, number of segments grafted, history of myocardial infarction, ejection fraction, and presence of unstable angina have estimated survivals not statistically less in any of these subsets than that of matched cohorts of the general population.

Purification and characterization of multiplication-stimulating activity (MSA) carrier protein

The rat liver cell line, BRL-3A, is known to produce a family of polypeptides referred to as multiplication-stimulating-activity (MSA). Serum-free conditioned medium from this cell line is a rich source for the purification of these somatomedin-like molecules. Somatomedins in serum, as well as MSA produced by BRL-3A cells in culture, exist primarily as a high molecular weight complex bound to specific carrier proteins. This study describes the purification of the MSA carrier protein (MCP) from conditioned medium using affinity chromatographic procedures. The purified carrier protein is shown to specifically bind labeled MSA and generates a complex with an apparent molecular weight of 60,000-70,000 daltons. Characterization of the carrier protein indicates that it consists of two different noncovalently linked protein chains with apparent molecular weights of 30,000 and 31,500 daltons. The availability of a pure carrier protein should provide a unique opportunity to investigate the functional significance of the carrier protein in the biological activity of the somatomedins.

Inhibition of biological activity of multiplication-stimulating activity by binding to its carrier protein

Multiplication-stimulating activity (MSA) produced by Buffalo rat liver cells (BRL-3A) in culture is related to the somatomedin family of growth regulatory polypeptides. MSA will stimulate glucose transport and DNA synthesis in normal chicken embryo fibroblasts (CEF) at concentrations of 10-200 ng/ml. MSA found in BRL-3A-conditioned medium, like the somatomedins in serum, does not exist as the free hormone but is bound to a specific high molecular weight carrier protein. In this report we demonstrate that purified MSA carrier protein (MCP) inhibits the biological activity of MSA on CEF as measured by the stimulation of glucose transport and DNA synthesis. In addition, purified MCP competitively inhibits the binding of 125I-labeled MSA to these cells. In control experiments in which insulin was used as the mitogenic agent, MCP had no effect on these biological responses. These results indicate that the inhibitory effect of MCP is the result of specific interaction with MSA and support the hypothesis that cells may be unresponsive to somatomedins bound to their serum carrier proteins.

Identification of somatomedin-like polypeptides produced by mammary tumors of BALB/c mice

A transplantable mammary tumor derived from an outgrowth of nodule-like alveolar lesions induced by 7,12-dimethylbenz[a]anthracene in cultures of whole mammary gland was shown to produce a family of somatomedin-like polypeptides when cultured in vitro. Minced mammary tumor tissue as well as monolayer cultures of tumor cells produced similar polypeptides when incubated in serum- and hormone-free medium. The polypeptides released into the medium ranged in molecular weight from 20,000 to 7,000 as determined by Sephadex G-50 chromatography under acidic conditions and analytical gel electrophoresis in acetic acid:urea. Because of their relative abundance, the M.W. 7000 polypeptides were partially purified and characterized. This preparation markedly stimulated DNA synthesis in chicken embryo fibroblast cultures and competed for the binding of 125I-labeled multiplication-stimulating activity to these cells. The binding of 125I-labeled epidermal growth factor to the surface of mouse embryo fibroblasts, in contrast, was not affected.

Regulation of amino acid transport in chicken embryo fibroblasts by purified multiplication-stimulating activity (MSA)

Enhanced amino acid transport is observed when quiescent cultures of chicken embryo fibroblasts are stimulated to proliferate by the addition of purified multiplication-stimulating activity (MSA). This increase in amino acid transport is an early event occurring prior to the onset of DNA synthesis in stimulated cells. Results indicate that the changes in transport activity, as measured by alpha-aminoisobutyric acid (AIB) uptake, are due to stimulation of only the Na+-dependent A transport system. There is little or no change in the activities of transport systems ASC, L, or Ly+ upon exposure to MSA. A kinetic analysis shows this increased activity is due to a change in Vmax while Km remains unaltered. Continuous exposure to the stimulus is required to maintain the increased level of transport activity and the presence of inhibitors of RNA and protein synthesis significantly inhibits the response. Results also indicate that a similar specific increase in the A transport system is initiated when RSV tsNY68 infected cells are shifted to the permissive temperature. It appears that the A system of mediation is emerging as a strategic regulatory site for cell function.

An evaluation of direct access radiology in general practice

An analysis of the use of direct access to radiology by 71 general practitioners in Scotland is described and is based on 2,596 x-ray examinations in 2,409 patients during a period of six months. Almost half of the patients had to travel more than five miles for their examinations, but time lost in travelling was a much less important factor than the interval elapsing before the requested examination was completed. Nearly one third waited at least two weeks. Referral for diagnosis was by far the commonest reason and direct access was estimated to save 270 hospital outpatient appointments per month. I believe that general practitioners under-use rather than abuse radiology, which might be extended by a selective system of appointments.

Regulation of the proliferative response in Rous sarcoma virus transformed chicken embryo fibroblasts by serum and multiplication-stimulating activity (MSA)

A temperature sensitive mutant of Rous sarcoma virus (tsNY68) was used to obtain cultures of quiescent virus-infected chicken embryo fibroblasts arrested by serum starvation at the non-permissive temperature. Upon shift to the permissive temperature, these cells enter the replicative cell cycle as evidenced by increases in 2-deoxyglucose uptake, 3H-thymidine incorporation and percent labeled nuclei. These changes occur in the absence of serum and the cells become morphologically transformed within eight to ten hours after the temperature shift. Entry into the S phase temporally resembles that of normal quiescent fibroblasts stimulated with serum. This experimental system was used to examine the proliferative response of transformed cells to serum and purified multiplication-stimulating activity (MSA) during the transition from the resting to the growing state. Data are presented which show that the presence of serum in the medium enhances the proliferative response of quiescent infected cells shifted to the permissive temperature over those shifted in the absence of serum. In contrast, the presence of MSA has no additional effect on the response exhibited by infected cells shifted to the permissive temperature in serum-free medium. Labeled MSA binding experiments show that this lack of response is not due to a loss of MSA receptors on the cell surface since transformed cells are still capable of binding MSA at the same level as normal cells. The results are consistent with the hypothesis that the set of biochemical events initiated by MSA in normal cells are turned on in infected cells shifted to the permissive temperature by the activation of the src gene product.

Preliminary studies of absorption and excretion of benoxaprofen in man

1 Benoxaprofen is a new acidic anti-inflammatory compound which was well absorbed after oral administration to man. 2 Single doses of 100, 200 and 400 mg produced mean peak concentrations in the plasma of 13.0, 33.5 and 45.3 microgram respectively, and the plasma half-life of the compound was between 30 and 35 hours. 3 Multiple dosing with 25 and 50 mg every 24 h achieved an equilibrium conentration in the plasma after 6-8 days, while dosing with 100 mg every 12 h enabled equilibrium to be reached in 3-6 days. Plasma concentrations between 35 and 45 microgram/ml were achieved by giving 100 mg doses every 12 hours. 4 Absorption of benoxaprofen was delayed when the drug was given with food, but the total amount absorbed remained the same. 5 The effect of milling the material to small particle size (19 micron) was to increase the rate of absorption compared to that of unmilled material (58 micron). 6 Benoxaprofen was well tolerated by healthy male subject in the doses given.