Cell-activation responses to cytomegalovirus infection relationship to the phasing of CMV replication and to the induction of cellular damage.
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Cell Division↗
Biomedical subjects
J M Russell
Publications and source records attributed to J M Russell.
Na+, K+, Cl- coupled transport in squid axon.
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Animals↗
Intracellular Ca2+ does not activate the SITS-sensitive anion transporter in barnacle muscle.
By means of the intracellular dialysis technique, we have measured 36Cl efflux from single barnacle muscle fibers and compared the effects of raising intracellular ionized calcium concentration [( Ca2+]i) to the effects of lowering intracellular pH (pHi). Lowering pHi by 1 unit or less resulted in a 20-fold stimulation of 36Cl efflux which occurred relatively rapidly and which could be inhibited by 90-95% by 4-acetamido-4'-isothio-cyanostilbene-2,2'-disulfonic acid (SITS). In contrast, raising [Ca2+]i as much as 250-fold resulted in a relatively small increase of 36Cl efflux. The small increase occurred after a long latency, developed slowly and could not be blocked or prevented by treatment with SITS. We conclude that the increase of the SITS-sensitive 36Cl efflux caused by a fall of pHi is not mediated by a rise of [Ca2+]i.
4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
pH-sensitive activation of the intracellular-pH regulation system in squid axons by ATP-gamma-S.
The regulation of intracellular pH (pHi) is essential for normal cell function, and controlled changes in pHi may play a central role in cell activation. Sodium-dependent Cl-HCO3 exchange is the dominant mechanism of pHi regulation in the invertebrate cells examined, and also occurs in mammalian cells. The transporter extrudes acid from the cell by exchanging extracellular Na+ and HCO3- (ref. 9) (or a related species) for intracellular Cl- (refs 3, 4). It is blocked by the stilbene derivatives DIDS (4,4'-diisothiocyano-stilbene-2,2'-disulphonate, ref. 10) and SITS (4-acetamido-4'-isothiocyano-stilbene-2,2'-disulphonate, ref. 3), and has a stoichiometry of two intracellular H+ neutralized for each Na+ taken up and each Cl- extruded by the axon. Because the inwardly-directed Na+ concentration gradient is sufficiently large to energize both the HCO3- influx and Cl- efflux, this electroneutral exchanger could be a classic secondary active transporter, thermodynamically independent of ATP hydrolysis. However, at least in the squid axon, the exchanger has an absolute requirement for ATP (ref. 3). Thus, a major unresolved issue is whether this Na-dependent Cl-HCO3 exchanger stoichiometrically hydrolyses ATP (the pump hypothesis), or whether ATP activates the transporter by a mechanism such as phosphorylation or simple binding (the activation hypothesis). We have now explored the role of ATP in pHi regulation by dialysing axons with the ATP analogue ATP-gamma-S. In many systems, ATP-gamma-S is an acceptable substrate for protein kinases, whereas the resulting thiophosphorylated proteins are not as readily hydrolysed by phosphatases as are phosphorylated proteins. Our results rule out the pump hypothesis, and show that the basis of the axon's ATP requirement is the pH-dependent activation (by, for instance, phosphorylation or ATP binding) of the exchanger itself, or of an essential activator.
Adenosine Triphosphate↗
A plasma membrane-enriched preparation from giant barnacle muscle fibers.
We describe a procedure for obtaining a highly enriched plasma membrane (sarcolemmal) preparation from muscle fibers of the giant barnacle (Balanus nubilus). The sarcolemmal-enriched portion migrated as a light fraction (F1) at the 10-24% sucrose interface. This fraction displayed saturable ouabain binding (Kd = 0.119 microM) that was enriched 10 times compared to that in the original homogenate. F1 was also prepared using muscle fibers previously labeled with 1,2-ditritio-1,2(2,2'-disulfo-4,4'-diisothiocyano)diphenylet hane, disodium salt [( 3H]-H2DIDS). F1 was enriched 25-fold in [3H]H2DIDS binding sites with respect to the homogenate. Ca2+-ATPase and succinic dehydrogenase-activities were low in F1, as was oxalate-supported Ca2+ uptake. Compared to membranes of sarcoplasmic reticulum origin, F1 was enriched in sarcolemma membranes by about 45-fold while it was enriched approximately 30-fold over mitochondrial membranes. Thus, F1 provides an extremely pure source of external muscle membranes.
4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
The interaction of intracellular Mg2+ and pH on Cl- fluxes associated with intracellular pH regulation in barnacle muscle fibers.
The intracellular dialysis technique was used to measure unidirectional Cl- fluxes and net acid extrusion by single muscle fibers from the giant barnacle. Decreasing pHi below normal levels of 7.35 stimulated both Cl- efflux and influx. These increases of Cl- fluxes were blocked by disulfonic acid stilbene derivatives such as SITS and DIDS. The SITS-sensitive Cl- efflux was sharply dependent upon pHi, increasing approximately 20-fold as pHi was decreased from 7.35 to 6.7. Under conditions of normal intracellular Mg2+ concentration, the apparent pKa for the activation of Cl- efflux was 7.0. We found that raising [Mg2+]i, but not [Mg2+]o, had a pronounced inhibitory effect on both SITS-sensitive unidirectional Cl- fluxes as well as on SITS-sensitive net acid extrusion. Increasing [Mg2+]i shifted the apparent pKa of Cl- efflux to a more acid value without affecting the maximal flux that could be attained. This relation between pHi and [Mg2+]i on SITS-sensitive Cl- efflux is consistent with a competition between H ions and Mg ions. We conclude that the SITS-inhibitable Cl- fluxes are mediated by the pHi-regulatory transport mechanism and that changes of intracellular Mg2+ levels can modify the activity of the pHi regulator/anion transporter.
4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
Vanadate and fluoride effects on Na+-K+-Cl- cotransport in squid giant axon.
The effects of vanadate and fluoride on the Na+-K+-Cl- cotransporter of the squid giant axon were assessed. In axons not treated with these agents, intracellular dialysis with ATP-depleting fluids caused bumetanide-inhibitable 36Cl influx to fall with a half time of approximately 16 min. In the presence of either 40 microM vanadate or 5 mM fluoride, the decay of bumetanide-inhibitable 36Cl influx was significantly slowed; half time for vanadate-treated axons is 45 min and for fluoride-treated axons is 37 min. These agents are not exerting their effects on Na+-K+-Cl- cotransport by influencing the rate of ATP depletion of the axon, since they had no effect on the ATP hydrolysis rate of an optic ganglia homogenate. We therefore suggest that these data support the hypothesis that Na+-K+-Cl- cotransport in squid axons is regulated by a phosphorylation-dephosphorylation mechanism and that vanadate and fluoride reduce the rate of dephosphorylation by inhibiting a protein phosphatase.
Adenosine Triphosphate↗
A way to measure hospital educators' productivity.
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Education Department, Hospital↗
Cervical carcinoma: prognosis in younger patients.
Retrospective analysis of 2870 patients with invasive carcinoma of the cervix treated by radiotherapy from 1971 to 1978 showed that the prognosis for younger patients (defined as either under 35 or under 40) was better than that for older age groups, but young patients presented with earlier disease. When the effect of stage on prognosis was also considered the improved survival of patients under 35 was confirmed, although the result was of only borderline significance. The better survival of younger patients was particularly noticeable for stage IB disease, the corrected five year survival of those under 35 being 93% compared with 79% for those over 35. On the basis of this analysis and a review of previous reports it is concluded that age alone is a poor indicator of prognosis and should not be used as an indication for adjuvant treatment. There is no evidence in this series of an aggressive form of cervical carcinoma in younger patients during the 1970s.
Adult↗
Physiology and biophysics of chloride and cation cotransport across cell membranes.
Many important questions remain to be answered about the mechanism that mediates coupled Na,K,Cl cotransport. We still do not know what the ATP requirement involves. Is ATP the direct energy source? Such an energy source does not seem to be necessary, inasmuch as the net free energy in the combined transmembrane chemical gradients of Na, K, and Cl is quite sufficient to maintain the observed high Cl(i). Could a protein kinase-mediated mechanism be responsible for the ATP requirement? How does reducing Cl(i) stimulate the transporter? What are the kinetic relationships for the co-ions at the outward- and inward-facing transport sites? Are they symmetrical? Can the squid axon regulate its cell volume? If so, is the Na,K,Cl transporter directly involved? Thus, the squid axon remains a fruitful preparation to study a transport mechanism similar to that found in a variety of cells. Its large size confers unique experimental advantages that should help us in our quest to understand this widely distributed transport mechanism.
Animals↗
Research in animal reproduction: An analysis of the contribution made by Latin America.
In an analysis carried out on the proceedings of the last two international congresses on animal reproduction and artificial insemination (1980 and 1984), a total of 944 papers presented were classified according to sex and species of the experimental animal, reproductive event studied, and country of origin. Latin America was found to be responsible for almost 10% of presentations, with Venezuela and Mexico making up half that total. The bovine species was the most studied both by Latin American countries (51.1%) and in general (42.7%). Approximately 15% of the Latin American contribution was concerned with goat studies versus 3.4% in general. Overall, the female was studied twice as much as the male. Fertility and estrous cycle were the reproductive events most studied both in general (36.3% and 31.6%, respectively) and by Latin American authors (27.2% and 33.3%, respectively). Latin American research concentrated on two main aspects: the effect of environment on reproduction and reproductive efficiency (25.8% and 13.7% of the total, respectively).
Journal Article↗
Coupled Na/K/Cl efflux. "Reverse" unidirectional fluxes in squid giant axons.
Studies of unidirectional Cl-, Na+, and K+ effluxes were performed on isolated, internally dialyzed squid giant axons. The studies were designed to determine whether the coupled Na/K/Cl co-transporter previously identified as mediating influxes (Russell. 1983. Journal of General Physiology. 81:909-925) could also mediate the reverse fluxes (effluxes). We found that 10 microM bumetanide blocked 7-8 pmol/cm2 X s of Cl- efflux from axons containing ATP, Na+, and K+. However, if any one of these solutes was removed from the internal dialysis fluid, Cl- efflux was reduced by 7-8 pmol/cm2 X s and the remainder was insensitive to bumetanide. About 5 pmol/cm2 X s of Na+ efflux was inhibited by 10 microM bumetanide in the continuous presence of 10(-5) M ouabain and 10(-7) M tetrodotoxin if Cl-, K+, and ATP were all present in the internal dialysis fluid. However, the omission of Cl- or K+ or ATP reduced the Na+ efflux, leaving it bumetanide insensitive. K+ efflux had to be studied under voltage-clamp conditions with the membrane potential held at -90 mV because the dominant pathway for K+ efflux (the delayed rectifier) has a high degree of voltage sensitivity. Under this voltage-clamped condition, 1.8 pmol/cm2 X s of K+ efflux could be inhibited by 10 microM bumetanide. All of these results are consistent with a tightly coupled Na/K/Cl co-transporting efflux mechanism. Furthermore, the requirements for cis-side co-ions and intracellular ATP are exactly like those previously described for the coupled Na/K/Cl influx process. We propose that the same transporter mediates both influx and efflux, hence demonstrating "reversibility," a necessary property for an ion-gradient-driven transport process.
Animals↗
Multivariate analysis of lipoprotein cholesterol fractions.
Intervention and prevention of multifactorial diseases such as coronary heart disease can be effective only when the joint effects of multiple risk factors are known. This process is facilitated by multivariate analysis of correlated risk factors, such as the serum cholesterol fractions, high density lipoprotein (HDL), low density lipoprotein (LDL), and very low density lipoprotein (VLDL). Whereas evidence for genetic covariation provides focus for further refined biochemical analysis, covariation among environmental factors can point to efficacious intervention strategies. To assess sources of variation and covariation among HDL, LDL, and VLDL, a multivariate path model was developed and applied to family data. Phenotypic variance is due primarily to specific environmental influences with substantial genetic influences, with the common family environment contributing less than 10% of the variance. There are genetic correlations of -0.22 for HDL-VLDL and 0.35 for VLDL-LDL, consistent with the known inverse associations of HDL and VLDL and the precursor-product relationship between VLDL and LDL, whereas there is no evidence for a direct HDL-LDL genetic relationship. Strong specific environmental correlations are found between HDL and VLDL (-0.35 in children and -0.50 in adults). Thus, intervention focused primarily on one fraction (e.g., triglycerides and VLDL) might beneficially affect levels of both lipoproteins (e.g., lowering VLDL cholesterol and elevating HDL cholesterol). Multivariate analysis can facilitate understanding of the linked effects of intervention on lipoprotein cholesterols, and, hence, should benefit approaches to maximize the effects of lipoprotein cholesterol intervention on coronary heart disease morbidity and mortality.
Analysis of Variance↗
Effects of pH changes on sodium pump fluxes in squid giant axon.
The effects of independently varying intracellular and extracellular pH on sodium pump fluxes were studied in the squid giant axon. By means of intracellular dialysis, we found that changes of intracellular pH (pHi), but not of extracellular pH, affected ouabain-sensitive Na+ efflux and K+ influx over the pH range of 6.0-8.6. Both fluxes were maximum at a pHi of 7.2-7.4. Variations away from this optimal pHi in either the acidic or alkaline direction resulted in a graded inhibition of both ouabain-sensitive fluxes. The kinetic basis for the inhibitory effect of acidic pHi was examined by comparing the kinetic parameters of activation of ouabain-sensitive sodium efflux by intracellular Na+ (Na+i) and extracellular K+ (K+o) at normal pHi with those at acidic pHi. We found that the inhibitory effect of intracellular acidity results from a reversible decrease in maximum velocity (Vmax), without an effect on the activation parameters for Na+i (K1/2 Na+i) or K+o (K1/2 K+o).
Animals↗
Robustness of path analysis of family resemblance against deviations from multivariate normality.
Path analysis is one of several methods available for quantitative genetic analysis, providing for both tests of hypotheses and estimates of relevant parameters. Central to the theory is the assumption that the observations follow a multivariate normal distribution within families. The purpose of the present investigation is to assess the effects of a certain type of departures from multivariate normality using quantitative family data on lipid and lipoprotein levels. The results show that even large departures produce reasonably unbiased parameter estimates. Whereas moderate departures lead to few inferential errors in hypothesis testing, gross departures from multivariate normality may have considerable effects on likelihood ratio tests.
Environment↗
Maximum-likelihood estimation of familial correlations from multivariate quantitative data on pedigrees: a general method and examples.
A general method for maximum-likelihood estimation of familial correlations from pedigree data is presented. The method is applicable to any type of data structure, including pedigrees in which variable numbers of individuals are present within classes of relatives, data in which multiple phenotypic measures are obtained on each individual, and multiple group analyses in which some correlations are equated across groups. The method is applied to data on high-density lipoprotein cholesterol and total cholesterol levels obtained from participants in the Swedish Twin Family Study. Results indicate that there is strong familial resemblance for both traits but little cross-trait resemblance.
Cholesterol, HDL↗
Pregnancy complicated by maternal hydrocephalus. A report of 3 cases.
The obstetric management of 3 women with stable hydrocephalus is presented. The few obstetric complications were unrelated to the maternal hydrocephalus, and specific management of the maternal condition was not necessary. Better management of hydrocephalus in infancy, as well as of the other forms of non-tumoral hydrocephalus, has led to more adults in a stable state with the condition and pregnancy will occur in some of these. A plea is made for all female patients with hydrocephalus to have a ventriculoperitoneal shunt rather than a ventriculoatrial one, with a view to reduction of complications in later pregnancies.
Adolescent↗