Protein kinase A is a functional component of focal adhesions

Focal adhesions (FAs) form the junction between extracellular matrix (ECM)-bound integrins and the actin cytoskeleton and also transmit signals that regulate cell adhesion, cytoskeletal dynamics, and cell migration. While many of these signals are rooted in reversible tyrosine phosphorylation, phosphorylation of FA proteins on Ser/Thr residues is far more abundant yet its mechanisms and consequences are far less understood. The cAMP-dependent protein kinase (protein kinase A; PKA) has important roles in cell adhesion and cell migration and is both an effector and regulator of integrin-mediated adhesion to the ECM. Importantly, subcellular localization plays a critically important role in specifying PKA function. Here, we show that PKA is present in isolated FA-cytoskeleton complexes and active within FAs in live cells. Furthermore, using kinase-catalyzed biotinylation of isolated FA-cytoskeleton complexes, we identify 53 high-stringency candidate PKA substrates within FAs. From this list, we validate tensin-3 (Tns3)-a well-established molecular scaffold, regulator of cell migration, and a component of focal and fibrillar adhesions-as a novel direct substrate for PKA. These observations identify a new pathway for phospho-regulation of Tns3 and, importantly, establish a new and important niche for localized PKA signaling and thus provide a foundation for further investigation of the role of PKA in the regulation of FA dynamics and signaling.

Protein Kinase A is a Functional Component of Focal Adhesions

Focal adhesions (FAs) form the junction between extracellular matrix (ECM)-bound integrins and the actin cytoskeleton and also transmit signals that regulate cell adhesion, cytoskeletal dynamics, and cell migration. While many of these signals are rooted in reversible tyrosine phosphorylation, phosphorylation of FA proteins on Ser/Thr residues is far more abundant yet its mechanisms and consequences are far less understood. The cAMP-dependent protein kinase (protein kinase A; PKA) has important roles in cell adhesion and cell migration and is both an effector and regulator of integrin-mediated adhesion to the ECM. Importantly, subcellular localization plays a critically important role in specifying PKA function. Here, we show that PKA is present in isolated FA-cytoskeleton complexes and active within FAs in live cells. Furthermore, using kinase-catalyzed biotinylation of isolated FA-cytoskeleton complexes, we identify fifty-three high-stringency candidate PKA substrates within FAs. From this list, we validate tensin-3 (Tns3) - a well-established molecular scaffold, regulator of cell migration, and component of focal and fibrillar adhesions - as a novel direct substrate for PKA. These observations identify a new pathway for phospho-regulation of Tns3 and, importantly, establish a new and important niche for localized PKA signaling and thus provide a foundation for further investigation of the role of PKA in the regulation of FA dynamics and signaling.

Using deterministic record linkage to link ambulance and emergency department data: is it possible without patient identifiers? A case study from the UK

INTRODUCTION

Routine linkage of emergency ambulance records with those from the emergency department is uncommon in the UK. Our study, known as the Pre-Hospital Emergency Department Data Linking Project (PHED Data), aimed to link records of all patients conveyed by a single emergency ambulance service to thirteen emergency departments in the UK from 2012-2016.

OBJECTIVES

We aimed to examine the feasibility and resource requirements of collecting de-identified emergency department patient record data and, using a deterministic matching algorithm, linking it to ambulance service data.

METHODS

We used a learning log to record contacts and activities undertaken by the research team to achieve data linkage. We also conducted semi-structured interviews with information management/governance staff involved in the process.

RESULTS

We found that five steps were required for successful data linkage for each hospital trust. The total time taken to achieve linkage was a mean of 65 weeks. A total of 958,057 emergency department records were obtained and, of these, 81% were linked to a corresponding ambulance record. The match rate varied between hospital trusts (50%-94%). Staff expressed strong enthusiasm for data linkage. Barriers to successful linkage were mainly due to inconsistencies between and within acute trusts in the recording of two ambulance event identifiers (CAD and call sign). Further data cleaning was required on emergency department fields before full analysis could be conducted. Ensuring the data was not re-identifiable limited validation of the matching method.

CONCLUSION

We conclude that deterministic record linkage based on the combination of two event identifiers (CAD and call sign) is possible. There is an appetite for data linkage in healthcare organisations but it is a slow process. Developments in standardising the recording of emergency department data are likely to improve the quality of the resultant linked dataset. This would further increase its value for providing evidence to support improvements in health care delivery.

HIGHLIGHTS

Ambulance records are rarely linked to other datasets; this study looks at the feasibility and resource requirement to use deterministic matching to link ambulance and emergency department data for patients conveyed by ambulance to the emergency department.It is possible to link these data, with an average match rate of 81% across 13 emergency departments and one large ambulance trust.All trusts approached provided match-able data and there was an appetite for data linkage; however, it was a long process taking an average of 65 weeks.We conclude that deterministic matching using no patient identifiers can be used in this setting.

Electric fields in active sites: substrate switching from null to strong fields in thiol- and selenol-subtilisins

Although known to be important factors in promoting catalysis, electric field effects in enzyme active sites are difficult to characterize from an experimental standpoint. Among optical probes of electric fields, Raman spectroscopy has the advantage of being able to distinguish electronic ground-state and excited-state effects. Earlier Raman studies on acyl derivatives of cysteine proteases [Doran, J. D., and Carey, P. R. (1996) Biochemistry 35, 12495-502], where the acyl group has extensive pi-electron conjugation, showed that electric field effects in the active site manifest themselves by polarizing the pi-electrons of the acyl group. Polarization gives rise to large shifts in certain Raman bands, e.g. , the C=C stretching band of the alpha,beta-unsaturated acyl group, and a large red shift in the absorption maximum. It was postulated that a major source of polarization is the alpha-helix dipole that originates from the alpha-helix terminating at the active-site cysteine of the cysteine protease family. In contrast, using the acyl group 5-methylthiophene acryloyl (5-MTA) as an active-site Raman probe, acyl enzymes of thiol- or selenol-subtilisin exhibit no polarization even though the acylating amino acid is at the terminus of an alpha-helix. Quantum mechanical calculations on 5-MTA ethyl thiol and selenol ethyl esters allowed us to identify the conformational states of these molecules along with their corresponding vibrational signatures. The Raman spectra of 5-MTA thiol and selenol subtilisins both showed that the acyl group binds in a single conformation in the active site that is s-trans about the =C-C=O single bond. Moreover, the positions of the C=C stretching bands show that the acyl group is not experiencing polarization. However, the release of steric constraints in the active site by mutagenesis, by creating the N155G form of selenol-subtilisin and the P225A form of thiol-subtilisin, results in the appearance of a second conformer in the active sites that is s-cis about the =C-C=O bond. The Raman signature of this second conformer indicates that it is strongly polarized with a permanent dipole being set up through the acyl group's pi-electron chain. Molecular modeling for 5-MTA in the active sites of selenol-subtilisin and N155G selenol-subtilisin confirms the findings from Raman spectroscopic studies and identifies the active-site features that give rise to polarization. The determinants of polarization appear to be strong electron pull at the acyl carbonyl group by a combination of hydrogen bonds and the field at the N-terminus of the alpha-helix and electron push from a negatively charged group placed at the opposite end of the chromophore.

Pharmacokinetics of pretargeted monoclonal antibody 2D12.5 and 88Y-Janus-2-(p-nitrobenzyl)-1,4,7,10-tetraazacyclododecanetetraacetic acid (DOTA) in BALB/c mice with KHJJ mouse adenocarcinoma: a model for 90Y radioimmunotherapy

Three-step pretargeting for radioimmunotherapy in BALB/c mice with KHJJ tumors was done with monoclonal antibody (mAb) 2D12.5, which is specific for yttrium-1,4,7,10-tetraazacyclododecanetetraacetic acid (DOTA) but nonspecific for the tumor. Tumor uptake was by passive diffusion of mAb through leaky neovasculature in the tumor. The three steps were: (a) anti-hapten mAb 2D12.5 (0 h); (b) polyvalent haptenprotein conjugate chase (20 h); and (c) 88Y-labeled monovalent DOTA or bivalent Janus-DOTA haptens (21 h) and organ and tumor bioassay (24 h). Rapid tumor (T) uptake and high tumor:blood ratio (T:BL) was seen 3 h after injection after step c. For monovalent 88Y-DOTA, T = 1.7%/g* and T:BL = 16:1; for bivalent 88Y-Janus-DOTA, T = 4.41%/g* and T:BL = 21:1 at 3 h (*, P < 0.001). Blood and bone plus marrow were << 1%/g, and liver was < 1%/g. The 24-h whole body retention was approximately 5% of injected dose with 1% in tumor (20% of total), 1.8% in other organs, and 2.2% in carcass; the 24-h whole body retention of covalent nonspecific antibody conjugates was > 80% of injected dose. The biological half-life in the tumor of 0.9 microCi 88Y-Janus-DOTA was approximately 24 h, measured daily for 5 days. Activity in microCi/g of tumor and blood for 90Y equimolar to the amount of 88Y injected (0.9 microCi 88Y = 0.744 pmol = 36.47 microCi 90Y) was used for calculating the area under the curve of tumor and blood in microCi-h/g of 90Y. The 90Y radiation absorbed dose (RAD) from multiplying microCi-h/g x the 90Y absorbed dose constant, 1.99 RAD-g/microCi-h, gave T = 89 RAD and BL = 3.7 RAD. The therapeutic ratio from RAD T:RAD BL = 24:1. These results indicate that pretargeting 90Y hapten-specific mAb for radioimmunotherapy has considerable promise.

Immunogenicity in rabbits and mice of an antibody-chelate conjugate: comparison of (S) and (R) macrocyclic enantiomers and an acyclic chelating agent

The macrocyclic bifunctional chelating agent 2-(p-bromoacetamidobenzyl)-1,4,7,10-tetraazacyclododecanetetraa cetic acid (BAD), forms inert metal complexes ideal for radioimmunotherapy. Kosmas et al. (Cancer Res., 52: 904-911, 1992) found 2-imminothiolane linker-(S)-BAD monoclonal antibody HMFG1 highly immunogenic in patients. We studied the immunogenicity of (S) and (R) enantiomers of 2-imminothiolane linker-BAD rabbit IgG, monoclonal antibody Lym-1, and Lym-1 2-imminothiolane linker-(S)-bromoacetamidobenzyl-EDTA in 15 rabbits. Five groups of three each were given 0.1, 1.0, or 10 mg of 111In conjugate i.v., blood samples were taken daily for 14 days and biweekly for 70 days, and the plasma T1/2 was calculated. A drop in plasma 111In at 6-8 days coincided with the appearance of antibody on enzyme-linked immunosorbent assay. Specific anti-(S)-BAD, anti-(R)-BAD, anti-(S)-bromoacetamidobenzyl-EDTA, and anti-mouse IgG were measured. Rabbit IgG conjugates did not elicit an immune response. Mouse IgG conjugates were immunogenic on the first exposure, with both anti-1,4,7,10-tetraazacylododecane N,N',N'',N'''-tetraacetic acid and anti-mouse responses. Anti-1,4,7,10-tetraazacylododecane N,N',N'',N'''-tetraacetic acid was specific for the (S) or (R) enantiomer, but cross-reaction appeared with reboosting. A second injection of the opposite enantiomer gave a response to that enantiomer. Lym-1 bromoacetamidobenzyl-EDTA produced anti-bromoacetamidobenzyl-EDTA and anti-mouse response.

Viability and biodistribution of 68Ga MPO-labelled human platelets

The viability and biodistribution of 68Ga-mercaptopyridine-N-oxide (MPO)-labelled autologous platelets was studied in 10 patients. The average platelet labelling yield was 36 +/- 12% and injected activity was 2.0 +/- 0.9 mCi 68Ga. The % activity in platelets per ml whole blood was 64 +/- 20% at 15 min-1.0 h postinjection and 76 +/- 14% at 2-4h. The average recovery of platelets (% injected platelets circulating in peripheral blood) was 31 +/- 21% at 15 min-1 h and 39 +/- 20% at 2-4 h. The positron emission tomographic (PET) images showed high circulating vascular background. Two patients had technically inadequate scans, and six were false negative due to high blood background. One patient with a massive pulmonary embolus occurring 24 h prior to scanning had marked uptake of 68Ga platelets in a large clot in the superior branch of the right main pulmonary artery. A second patient, with 68Ga platelets circulating during angioplasty of a left posterior tibial artery stenosis, had intense uptake in the lesion shown on the PET scan obtained 4 h following the procedure. These results indicate good viability of 68Ga-MPO-labelled autologous human platelets, but poor visualization of clots by PET imaging, due to the high blood background at early times.

Pretargeted immunoscintigraphy: effect of hapten valency on murine tumor uptake

A method of radioimmunoscintigraphy using bivalent "Janus" haptens with an apparent enhanced affinity ("avidity") for the antibody is described. Janus with 50 micrograms pretargeted Mab WC3A11 resulted in significantly higher murine tumor concentrations (approximately 7%/g) compared to monovalent haptens (approximately 1.4%/g, p < 0.001), and the same high tumor-to-background ratios (approximately 3/1). Janus was synthesized by coupling two molecules of BABE together with a 1,4 butanedithiol linker. Janus itself was rapidly excreted (T1/2b = 42 min) by the kidneys and did not concentrate in any other organs or tissues. Three-step pretargeted immunoscintigraphy (binder, chaser, tracer) with 111In- or 67Ga-Co(III) Janus produced excellent mouse tumor images in 3 hr with high tumor-to-background ratios. The use of short-lived tracers, such as 99mTc and 68Ga, with a T1/2p of hours to image antibodies that localize slowly over several days in vivo is accessible with this new technology.

Pre-targeted immunoscintigraphy of murine tumors with indium-111-labeled bifunctional haptens

A method of tumor imaging utilizing the nonspecific accumulation of antibody through leaky capillaries is described, in which the antibody and the radiolabel are administered separately. Nonradioactive antibody is given first (pre-targeted), and allowed adequate time to reach maximum tumor concentration. Depending on the antibody, this may take several days. At the time of maximum tumor concentration of nonradioactive antibody, the blood is quickly cleared of excess circulating nonradioactive antibody using a special i.v. "chase". The radiolabel then is given and imaging done in 1 to 3 hr. The use of short lived tracers (hours) to image antibodies that localize slowly (days) in-vivo is made possible by this method.

Metal decomposition rates of 111In-DTPA and EDTA conjugates of monoclonal antibodies in vivo

We have studied the metal chelate decomposition rates in vivo in both 111In-labelled benzyl EDTA and DTPA (bicyclic anhydride) conjugates of monoclonal anti-IAk IgG2a with identical Ka = 1 X 10(11)M-1 in both Ag+ve and Ag-ve mice. Twenty mu Ci was given i.v. and whole body counting done immediately and daily for 10 days, with six to eight mice in each group. Half the mice in each group received i.p. injections of 5.0 mg CaNa2 EDTA chase (Versenate) to facilitate urinary excretion of free 111In. 50% of control 111In-citrate remained at nine days but only 8% with chase. No significant loss of 111In with chase occurred with C1 substituted EDTA conjugates. A 19% increase in excretion was demonstrated with the chase in mice given DTPA conjugates (1.9% per day). While this will not interfere with radioimmunoimaging up to 24 h after injection, waiting periods of a week or longer will produce significant background of free 111In in the reticuloendothelial system, RES. 111In-EDTA stability was important in accurate metabolic rate measurements of anti-IAk; T1/2 = 7.0 days in Ag-ve mice, T1/2 = 9.3 days in Ag-ve mice. It will be important to measure the in vivo rates for each new metal complex, especially those intended for therapy such as Y-90.

Monoclonal antibody hapten radiopharmaceutical delivery

One hundred micrograms of monoclonal antibody (MoAb) CHA255 with a binding constant Kb of 4 X 10(9) was complexed with indium-111 labelled BLEDTA II, BLEDTA IV, benzyl EDTA, and an EDTA conjugate of Fab. The 24-h tumour and organ distribution of BALB/c mice bearing KHJJ tumours was studied for each compound alone, the antibody complex, and 3 h following a chelate chase of the antibody complex. Whole body biological half-life was measured for 7 days with and without a chelate chase for each antibody complex. The 24-h whole body counts dropped 20 to 60% and blood concentration fell over 89% within 3 h of administering the chelate chase. Theoretical equivalent human organ doses were calculated from the 24-h organ concentrations, effective half-life, and MIRD 11 S values (absorbed dose per cumulated activity). Liver and spleen were the target organs, with the dose ranging from 0.50 to 3.91 rads mCi-1. The reduction in organ radiation dose varied up to 95% following the chelate chase. Rapid selective renal clearance of chelate labelled radiopharmaceuticals by competitive inhibition (chelate chase) of their reversible binding to monoclonal antibodies enhances tumour imaging and improves the radiation dosimetry.

Monoclonal antibodies as reversible equilibrium carriers of radiopharmaceuticals

We have prepared monoclonal antibodies (MoAbs) with the specific ability to bind metal chelates such as 111In benzyl EDTA. One, 10, 50 and 100 micrograms MoAb CHA255 Kb = 4 X 10E9 was complexed with 111In BLEDTA II, BLEDTA IV, and benzyl EDTA and injected i.v. in Balb/c mice with KHJJ tumor. The biological half-life by whole body counting was profoundly altered for all three compounds; from minutes to hours with 10 micrograms; to days with 100 micrograms. Tumor uptake increased 50 fold at 24 h with increasing MoAb but satisfactory tumor concentrations (3% per g) and tumor/blood ratios (1.8:1) were obtained with an amount equivalent to 7 mg for a human. Blood level and whole body activity were decreased 30-50% within 3 h or i.v. injection of a "flushing" dose of unlabeled indium benzyl EDTA, increasing tumor/blood ratios to 50:1.

Nerve growth factor and other agents mediate phosphorylation and activation of tyrosine hydroxylase. A convergence of multiple kinase activities

A rapid phosphorylation of tyrosine hydroxylase occurs in the PC12 nerve-like clonal cell line in response to nerve growth factor (NGF), epidermal growth factor (EGF), dibutyryl-cAMP, cholera toxin, phorbol- 12-myristate-13-acetate (PMA), or potassium depolarization in the presence of calcium ions. Complete tryptic digestion and two-dimensional peptide mapping reveals four available sites of phosphorylation in the enzyme. Phosphoamino acid analysis demonstrates that serine is the amino acid residue phosphorylated in each peptide. Specific phosphorylation of each of the four sites is achieved by different subsets of the above agents. One peptide site is phosphorylated in response to EGF alone. A second site is phosphorylated only in response to NGF, cholera toxin or dibutyryl-cAMP. A third site is phosphorylated only in response to potassium depolarization and requires the presence of extracellular Ca2+. The fourth site is the only site phosphorylated in response to PMA. These data indicate that at least 4 distinct kinase systems can act to phosphorylate tyrosine hydroxylase in PC12 cells. The PMA-stimulated peptide site is also phosphorylated in response to every one of the other agents. Further proteolytic digestions and phosphopeptide mapping of this common peptide, using Staphylococcus V8 protease and thermolysin, did not generate different phosphopeptides resulting from the different agents. These data suggest that the phosphorylation of this common peptide in response to all of the agents may be mediated by a common kinase, and, hence, that tyrosine hydroxylase phosphorylation by some agents may be mediated by two kinases. Although phosphopeptide maps of tyrosine hydroxylase resulting from cAMP elevation or NGF are qualitatively similar, quantitative differences exist, suggesting differential regulation of the same kinases by these agents. Tyrosine hydroxylase was found to be activated 2--4-fold in response to each phosphorylating agent. Thus, NGF and EGF present novel, natural means of regulating the activation state of tyrosine hydroxylase in responsive neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies against metal chelates

Because monoclonal antibodies can recognize and bind to specific groups of atoms such as tumour antigens, they have promise for use in vivo as carriers of radionuclides, drugs or other appended molecules for diagnosis and treatment of disease. Attachment of metal ions to antibodies by means of bifunctional chelating agents can add the diverse nuclear, physical and chemical properties of the metallic elements to these specific binding proteins (ref. 4 and refs therein). With the ultimate aim of engineering probe-binding properties into the antibodies themselves, we have now prepared monoclonal antibodies against the EDTA chelate of indium. These antibodies show a remarkable preference for indium chelates; changing to another metal such as scandium or gallium can decrease the antibody-binding constant by more than three orders of magnitude. These antibodies also introduce a new degree of control over the biological distributions of chelated radionuclides, markedly altering their uptake in tumours and normal organs.

Chelate conjugates of monoclonal antibodies for imaging lymphoid structures in the mouse

Radiolabeling of a mouse monoclonal antibody (MoAb) specific for the mouse histocompatibility alloantigen IAk expressed by the B lymphocytes of BALB/k and C3H mice but not BALB/c mice was performed by mixing the chelate-labeled anti (alpha) IAk MoAb with purified, no-carrier-added 111In citrate. Labeling efficiency was 85-95%, and the labeled alpha IAk MoAb retained its antigen binding properties in vitro and in vivo. The organ, spleen, and lymph node distribution of intravenously and subcutaneously administered 111In alpha IAk MoAb was compared in mice, two IAk positive and one IAk negative strains, and to 125I alpha IAk MoAb in one IAk positive strain. The 111In alpha IAk MoAb was more stable in vivo compared to 125I alpha IAk MoAb, as shown by a much slower excretion and a higher absolute uptake in lymph nodes and spleen. Lymph node to blood ratio was increased twofold by intravenous anti-EDTA MoAb. Subcutaneous injection permitted clear images of the tiny lymph nodes in the mouse. Potential clinical applications of 111In alpha lymphocyte MoAb include localization of normal lymph nodes and T & B cell leukemias and lymphomas, as well as detecting lymphatic metastases of other cancers. Therapy may also be possible using MoAbs labeled with beta-emitting metal ions such as yttrium-90.

Conjugation of antibodies with bifunctional chelating agents: isothiocyanate and bromoacetamide reagents, methods of analysis, and subsequent addition of metal ions

Preparation of the chelating agent (S)-4-[2,3-bis[bis(carboxymethyl)am ino]propyl]phenyl isothiocyanate is reported. Procedures for conjugation of this and (S)-N-4-[2,3-bis[bis-(carboxymethyl)amino] propyl]phenyl bromoacetamide to monoclonal antibodies and other proteins are described. The conjugates may be purified quickly by centrifugation through Sephadex G-50. The number of protein-bound chelating groups may be measured by titration with standard 57Co2+, using thin-layer chromatography to monitor binding. The labeled products retain their immunoreactivity, as illustrated by experiments in vivo with chelate-conjugated antibody to mouse I-AK antigen.

Use of specific antibody for rapid clearance of circulating blood background from radiolabeled tumor imaging proteins

A major problem that arises when radiolabeled serum proteins are used for tumor imaging is the presence of a large amount of circulating background activity that persists for several days. This delays imaging for at least 2 days following injection and necessitates computer subtraction of simulated background (second radiopharmaceutical injection) which introduces artifacts that are difficult to control. We propose here the injection of specific antibody immediately before imaging as an alternate way of reducing blood background through clearance of the immune complex by the liver. 111In-alkyl human transferrin and IgG were injected IV in BALB/c tumor mice, and followed in 18 h by anti-human transferrin and anti-human IgG antibody IV. Two hours later, the tumor and organ distribution of activity was compared with control mice not receiving antibody. 111In-transferrin blood activity was reduced to 1/48 of control with no decrease in tumor concentration: as a result, the tumor to blood ratio increased from 1.4:1 to 78:1. 111In-IgG blood activity was reduced to 1/17 of control, again with no decrease in tumor. The tumor to blood ratios increased from 0.7:1 to 17:1. The liver picked up most of the blood activity with none of the complex going to spleen, bone marrow, or kidney. Dog experiments showed clearance of blood was 90% complete in less than 15 min following antibody injection. Simultaneous scintillation images showed complete clearance of activity from the heart and great vessels in the chest and neck, and over the abdomen, with a concomitant increase in liver activity but no increase in spleen, kidney, or bone marrow activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between sodium transport and oxygen consumption in the isolated perfused rat kidney

The purpose of the present experiments was to determine the relationship between Na+ transport and O2 consumption of the perfused rat kidney in vitro. The delta Na/delta O2 ratio was calculated from the change in Na+ transport and the change in O2 consumption. Na+ transport was varied by lowering perfusion pressure or adding ouabain. Previous investigators have calculated the delta Na/delta O2 ratio for the kidney in vivo by combining all data points in each group of experiments. Using this approach, the delta Na/delta O2 ratio of the perfused kidneys was 66.3 +/- 22.0 for the low pressure perfusion experiments and 29.1 +/- 3.1 for the ouabain experiments. These values are at least as great as those reported for the kidney in vivo. The delta Na/delta O2 ratios were also calculated by determining the regression line for each individual kidney, and then obtaining the mean of these regressions. Using this approach, the delta Na/delta O2 ratio for the low pressure perfusion experiments was 37.0 +/- 7.4 and the delta Na/delta O2 ratio for the ouabain experiments was 20.3 +/- 1.7. These values are significantly lower than the ratios obtained by combining all data points. The ratio of absolute Na+ transport to absolute O2 consumption (Na/O2 ratio) was 13.1 +/- 0.5 for control experiments. This value is considerably less than that obtained for the kidney in vivo. The extrapolated rate of O2 consumption in the absence of sodium transport (i.e. nontransport metabolism) was 40-63% of the control rates of oxygen consumption; this is a much higher fraction of 'nontransport' metabolism than in the kidney in vivo. It is concluded that the metabolic efficiency of the perfused kidney is considerably less than that of the kidney in vivo. Furthermore, the present results cast doubt on the usefulness of the delta Na/delta O2 ratio as in index of efficiency of Na+ transport by the kidney.

Mechanism of cis-platinum nephrotoxicity: I. Effects of sulfhydryl groups in rat kidneys

cis-Diamminedichloroplatinum (CP), an important chemotherapeutic agent, produces acute renal failure by an unknown mechanism. Other heavy metals, such as mercury, are thought to be nephrotoxic by reacting with sulfhydryl (SH) groups. To investigate the mechanism of CP nephrotoxicity, F344 rats were injected once with 6 mg of CP per kg. After 96 hr, the blood urea nitrogen rose to 140 mg/100 ml. The SH concentration in control kidneys was 20.4 +/- 0.1 muml/g wet weight. Total renal SH groups decreased to a maximum of 14% at 120 hr (P less than .01). The fall in SH groups was entirely due to a decrease of protein-bound SH groups. Cell fractionation studies showed that the greatest decline of SH groups occurred in the "mitochondrial" and "cytosol" fractions. These fractions also had the highest Pt concentrations. There was no stoichiometric relationship between Pt accumulation and the change in SH groups. Furthermore, in vitro studies demonstrated that CP does not directly interact with SH groups. To determine if the change in renal SH groups was nonspecific effect of acute injury, renal failure was induced with glycerol (5 g/kg i.m.). Total SH groups per kidney increased after glycerol. These results indicate that the decrease in renal SH groups produced by CP is not due to nonspecific tubular necrosis. The present findings suggest the possibility that the nephrotoxic effects of CP may be related to depletion of SH groups. However, a direct cause-effect relationship has not been established.

Mechanism of active chloride transport by urinary bladder of the Colombian toad

In order to investigate the mechanism of active chloride transport, experiments were performed to verify the previous report that removal of potassium from the solutions bathing the urinary bladders of Colombian toads induced a reversal of short-circuit current (RSCC) and active chloride transport. The present experiments confirmed these findings. However, there was no correlation between the magnitude of the RSCC and the chloride transport. Furthermore, removal of chloride from the mucosal bathing solutions did not markedly affect the RSCC, indicating that the chloride transport was electrically silent. Removal of bicarbonate from the bathing solutions eliminated the RSCC, and acetazolamide inhibited both the RSCC and net chloride transport. These findings suggest a relationship between chloride and hydrogen ion transport. Inhibition of sodium transport by removal of sodium or addition of ouabain or amiloride has previously been shown to produce an RSCC. In the present experiments these same maneuvers caused an RSCC and induced net chloride transport. It is concluded that active chloride transport by Colombian toad bladder is stimulated by inhibition of sodium transport. The inhibition of active chloride transport by acetazolamide suggests a possible role for carbonic anhydrase in this process.

The effects of cosmic Particle radiation on pocket mice aboard Apollo XVII: V. Preflight studies on tolerance of pocket mice to oxygen and heat. Part I. physiological studies

Tests were carried out on pocket mice to ascertain their tolerance to elevated oxygen pressures alone and to a combination of hyperoxta and heat in excess of that expected during the flight of the mice on Apollo XVII. the mice withstood oxygen partial pressures up to 12 pst at normal room temperature (24 degrees C, 75 degrees F) over a period of 7 days. A few mice previously exposed to increased PO2 died in the course of exposure to an oxygen pressure of 10 pst or 12 psi (517 mm or 620 mm Hg) for 13 d in ambient heat of 32 degrees C (90 degrees F). Supplemental vitamin E and physiological saline loading given prior to exposure had no apparent protective effect. The overall conclusion was that the pocket mice which were to go on Apollo XVII could readily survive the ambient atmosphere to which they would be exposed.