Confirmation of two-step model of glucocorticoid hormone action in a glucocorticoid-sensitive human lymphoid cell line

The hypothesis that the intracellular distribution of free receptors for glucocorticoids is dependent upon a partitioning between cytoplasm and nucleus according to the free receptor and water content of each compartment has been tested in a glucocorticoid-sensitive human lymphoid cell line. The results confirm that at least in this human lymphoid cell line free unbound receptors for glucocorticoids are confined to the extranuclear (cytoplasmic) compartment and that nuclear translocation of these is dependent upon prior binding to steroid. These results do not support the hypothesis tested and are more consistent with the conventional “two-step” model of steroid hormone action.     

Microhabitat use by European rabbits (Oryctolagus cuniculus) in central Chile: Are adult and juvenile patterns the same?

Summary Rabbits (Oryctolagus cuniculus) have been recently introduced to central Chile; adult rabbits have been previously reported to exhibit a release in their use of microhabitats due to lack of effective predation upon them. This paper shows that kittens and juvenile rabbits do not exhibit the same microhabitat use pattern as adults, in spite of the very low predation pressure upon them. These results suggest that small rabbits are ecologically comparable to native rodents.     

Cathepsin B2 measurement by sensitive fluorometric ammonia analysis

A procedure has been developed for the measurement of cathepsin B2 activity that is based upon highly sensitive fluorometric ammonia analysis. The fluorochrome results from the reaction of phthaldehyde and mercaptoethanol with ammonium salts at pH 7.4. The method is sensitive in the range of 5–400 nmoles ammonium salt/ml. The assay is highly specific for ammonia since amino acids, peptides, amines, and amides do not interfere. Likewise, other components of the cathepsin B2 reaction system do not interfere. The most distinct advantage of the method is that the awkward diffusion step of most routine ammonia analyses can be eliminated.     

The localization of radioactive cesium in bovine muscle tissue]

The form in which radioactive caesium is present in muscular tissue has been investigated. It has been found that protein agents under study do not form stable complexes with radioactive caesium. It is suggested that caesium-137 is partially bound by muscular cell membranes upon meet storage.     

Suppression of appetitive behavior in the rat by naloxone: lack of effect of prior morphine dependence

Naloxone (0.3–10 mg/kg) produced a dose-related suppression of eating and drinking in rats that had been deprived of food for 48 hr or water for 24 hr. The suppression of water intake by naloxone was unaltered in rats that had been physically dependent upon morphine one week earlier and which were tolerant to the analgesic effect of morphine at the time naloxone was tested. These results confirm the ability of naloxone to suppress appetitive behavior in the rat but do not resolve the issue of whether or not this effect of naloxone is the consequence of an interaction with an endogenous opioid system.     

A Smear Technic for Demonstrating Cell Inclusions with Characteristics of Both Mitochondria and Bacteria

Cytoplasmic inclusions of various types of cells have been investigated by macerating or smearing and fixing and staining by different mitochondrial methods of technic. The results obtained as regards granular, rod-like, filamentous and globular forms immediately suggest a relation between these and similar cell inclusions which have in the past been described as mitochondria in certain cases of this material. While mechanical disturbance and drying before fixation apparently do not alter the staining properties of these forms, alcohol produces somewhat variable results depending upon the kind of material being investigated. Results indicate the presence in these smears of numerous intracellular bacteria, readily misinterpreted as mitochondria. In addition, there occur in certain cells, both in smears and sections, inclusions of indeterminate nature.     

Regulation of ribulose diphosphate formation in vivo by light

Light-dependent formation of ribulose-1,5 diphosphate is completely inhibited by low concentrations of 3-(3,4-dichlorophenyl)-1,1-dimethylurea which do not severely affect cyclic photophosphorylation. Also in Scenedesmus mutant number 11, capable of cyclic photophosphorylation, cellular ribulose-1,5 diphosphate-levels do not increase upon illumination. When mutant cells are H₂ adapted, however, a light-dependent formation of ribulose-1,5 diphosphate is observed in the presence of H₂. From these results it has been concluded that at least part of the Calvin cycle does not operate in the dark, since a reductant is lacking which is generated in the light.     

Liberation of asexual propagules in the Mucorales

The liberation of asexual propagules in the Mucorales was investigated by means of wind-tunnel experiments. Some species do not liberate propagules into an air stream, others liberate single spores or groups of spores. The effect of the relative humidity of the air stream upon propagule liberation has also been considered.     

Studies of Enzyme Polymorphisms in the Kamuela Population of D. MERCATORUM. I. Estimation of the Level of Polymorphism

A Kamuela, Hawaii, population of Drosophila mercatorum was surveyed for enzyme variability. The mean heterozygosity and the proportion of polymorphic loci were estimated as 0.1255 and 0.37, respectively. Neither deviates more than one standard error from their respective means for 43 Drosophila species (Nevo 1978). Heterozygosity was distributed across enzyme categories in much the same manner as observed in other species (Gillespie and Kojima 1968; Johnson 1974), and enzymes associated with glycolysis were about as variable as other enzymes of central metabolism.--The levels of heterozygosity and polymorphism in this population do not seem to have been affected by a low-level capacity for parthenogenesis. The observed parthenogenetic reproduction is not strongly associated with particular allelic variants among viable parthenogenetic adults; however, the capacity to establish a self-sustaining parthenogenetic clone is strongly associated with the phenotype with the most frequent allele at every locus studied. We interpret these results to mean that isozyme variants do not strongly influence viability under total homozygosity (the genetic condition imposed by parthenogenesis), but they do have an impact upon the reproductive biology of parthenogenetic adults.     

Synthesis and antimicrotubule activity of combretatropone derivatives

Combretatropone is a hybrid of combretastatin and colchicine in which the o-methoxyphenol of dihydrocombretastatin A-4 is replaced by an alpha-methoxytropone. Derivatives of combretatropone have been synthesized and evaluated for antimicrotubule activity. All combretatropones were less active than the corresponding colchicine derivatives, supporting the idea that loss of ligand conformational entropy upon tubulin binding results in decreased potency for colchicinoid ligands. The structure-activity relationship of the combretatropone series was different than that of the colchicine series. These data indicate that conformationally mobile and conformationally rigid colchicinoids do not interact with the receptor site in the same manner.     

The intracellular domain of p75NTR as a determinant of cellular reducing potential and response to oxidant stress

The low-affinity neurotrophin receptor, p75NTR, has been found to be pro- or anti-apoptotic depending upon the cell in which it is expressed. Reactive oxygen species play a major role in apoptosis induction and enactment. Using two polyclonal PC12 populations that, respectively, do or do not express p75NTR, this paper demonstrates that p75NTR expression confers resistance to oxidant stress upon PC12 cells maintained in serum-containing medium. The effect of p75NTR on cell survival is mimicked in p75-negative cells by expression of constructs that produce the p75NTR intracellular domain (ICD) or p75NTR with the extracellular domain deleted (DeltaECD), suggesting that binding of an extracellular ligand to p75NTR is not required. Our studies further document that the differential sensitivity to oxidant stress is serum-dependent and associated with differential oxidation of glutathione between p75-positive and p75-negative cells. These results suggest that the role of p75NTR in determining the consequences and treatment of age-related disorders and conditions in which reactive oxygen species are involved may require neither the extracellular receptor domain nor, by inference, the cognate extracellular ligands of this neurotrophin receptor.     

Chemical modification of lysine residues in bacterial formate dehydrogenase

Specific modification of 4.4 lysine residues per molecule of formate dehydrogenase, from the methylotrophic bacterium Achromobacter parvulus I by pyridoxal, results in complete inactivation of the enzyme. The concentration effect of the modifying agent and substrates on the inactivation of formate dehydrogenase has been studied. Coenzymes do not protect the enzyme from inactivation. Complete maintenance of enzyme activity was achieved in the presence of saturating concentrations of the formate and upon formation of the ternary complex, enzyme-NAD-azide. Formate specifically protects two lysine residues per dimer molecule of the enzyme from modification. The presence of one essential lysine residue in the substrate-binding region of the enzyme active site is assumed.     

Results of surgical lengthening of the short nose in the bilateral cleft lip patient

Some children with bilateral cleft lips do not grow a long enough nose and require surgical lengthening of the nose. We review our 12-year experience with a one-stage slide operation to achieve this. Seven males and 5 females had this operation at ages 7 through 13 years, and we have followed them from 6 months to 12 years. The results, and the subsequent growth effects are described. In general, good long-term improvement has been achieved and the external scars have not proved to be a major drawback. Subsequent procedures upon the columella, alae, and upper lip are often required to establish an unobtrusive nasal appearance.     

The integrated form of the Brody effect

We have considered the simplest model of the Brody effect: a circular inhomogeneity into a conducting medium of infinite extent energized by a source sink pair near the disk. To correlate with the reciprocal field equations, the Brody effect has been calculated in its integrated form by the Gabor-Nelson method (1954). In these conditions, our results do not depend upon any singular position on the closed contour; they are also invariable with respect to grounding the inhomogeneity and/or shifting the inhomogeneity centre from that of the compartment around it. Contrariwise, characterizing the Brody effect by an enhancement factor of local potential values is sensitive to the above factors and so, may become confusing because inducing the belief that the effect due to an inhomogeneity intrinsically depends upon removing the point from which it is viewed.     

Influence of chemical modification of cysteine and histidine side chains upon subunit reassembly of alpha crystallin

Alpha crystallin, the important multimeric structural protein of mammalian eye lens, is an assembly composed of 30 alpha-A and 10 alpha-B subunits. The influence of either partial or complete chemical modification of two important amino acid side chains, cysteine and histidine, upon the integrity of native alpha crystallin assembly and also upon the mode of subunit reassembly has been investigated. It has been found that chemical modification of surface-exposed cysteine and histidine side chains does not affect the subunit-subunit interactions stabilizing the native aggregate. Cysteine modifications, either partial or complete, unlike histidine modifications, do not seem to affect the backbone conformation of the subunits refolded after denaturation. Both cysteine and histidine modifications, however, affect the packing of the refolded structural elements forming the tertiary structure of the subunits and also the mode of oligomeric reorganization. The most striking effect of histidine modification is the considerable increase in size of the aggregates upon reassociation of the modified subunits. The chaperone activity, however, has been found to remain almost unaffected in spite of these chemical modifications.     

Influence of chemical modification of cysteine and histidine side chains upon subunit reassembly of alpha crystallin

Alpha crystallin, the important multimeric structural protein of mammalian eye lens, is an assembly composed of 30 alpha-A and 10 alpha-B subunits. The influence of either partial or complete chemical modification of two important amino acid side chains, cysteine and histidine, upon the integrity of native alpha crystallin assembly and also upon the mode of subunit reassembly has been investigated. It has been found that chemical modification of surface-exposed cysteine and histidine side chains does not affect the subunit-subunit interactions stabilizing the native aggregate. Cysteine modifications, either partial or complete, unlike histidine modifications, do not seem to affect the backbone conformation of the subunits refolded after denaturation. Both cysteine and histidine modifications, however, affect the packing of the refolded structural elements forming the tertiary structure of the subunits and also the mode of oligomeric reorganization. The most striking effect of histidine modification is the considerable increase in size of the aggregates upon reassociation of the modified subunits. The chaperone activity, however, has been found to remain almost unaffected in spite of these chemical modifications.     

The use of gas-phase substrates to study enzyme catalysis at low hydration

Although there are varying estimates as to the degree of enzyme hydration required for activity, a threshold value of ca. 0.2 g of water per gram of protein has been widely accepted. The evidence upon which this is based is reviewed here. In particular, results from the use of gas-phase substrates are discussed. Results using solid-phase enzyme-substrate mixtures are not altogether in accord with those obtained using gas-phase substrates. The use of gaseous substrates and products provides an experimental system in which the hydration of the enzyme can be easily controlled, but which is not limited by diffusion. All the results show that increasing hydration enhances activity. The results using gas-phase substrates do not support the existence of a critical hydration value below which enzymatic activity is absent, and suggest that enzyme activity is possible at much lower hydrations than previously thought; they do not support the notion that significant hydration of the surface polar groups is required for activity. However, the marked improvement of activity as hydration is increased suggests that water does play a role, perhaps in optimizing the structure or facilitating the flexibility required for maximal activity.     

Is DNA unwound by the cyclic AMP receptor protein?

Superhelical pBR 322 derivatives have been relaxed by eukaryotic topoisomerase I in the presence or in the absence of E. coli cyclic AMP receptor protein (CRP) and of cyclic AMP (cAMP). CRP alone, or cAMP alone do not affect the average linking number of the distribution of the relaxed topoisomers. Hence, they do not unwind the template. In the presence of cAMP, CRP induces a small unwinding. The extent of this unwinding is barely modified when the relaxation is carried out on a similar vector plasmid where the CRP binding site of the lac or of the gal operon has been inserted. Under these conditions, we checked that CRP occupies the lactose control site and that upon addition of RNA polymerase, the corresponding promoter is readily activated. These findings are difficult to reconcile with the proposal that activation of these promoters results from the binding of the CRP-cAMP complex to left-handed DNA sequences.     

The Structural Implications of the Linear Electrical Properties of Cardiac Purkinje Strands

An attempt has been made to decide upon the most reasonable equivalent circuit that will describe the passive linear properties of the Purkinje strands of sheep heart muscle. In order to do this, measurements were made of the phase angle of the characteristic admittance as well as the longitudinal impedance, both as functions of frequency. The results of both types of experiments indicate the presence of a longitudinally oriented capacity with a time constant of about 60–70 µsec. It is suspected that this capacity and time constant represent the connection between the cells, both radially and longitudinally. The plasma membrane contains another capacity with a time constant of about 15 msec.     

Inhibitors of the ATP/ADP antiporter suppress stimulation of mitochondrial respiration and H+ permeability by palmitate and anionic detergents

The action of ATP/ADP-antiporter inhibitors upon the uncoupling effect of palmitate, detergents and 'classical' uncouplers has been studied. The uncoupling effect was estimated by stimulation of succinate oxidation and of H+ permeability of rat liver mitochondria in the presence of oligomycin. It is shown that carboxyatractylate (CAtr) and pyridoxal 5-phosphate (PLP) suppress the uncoupling induced by palmitate and the anionic detergents SDS and cholate, but do not affect that induced by the cationic detergents CTAB, by the non-ionic detergent Triton X-100, as well as by the 'classical' uncouplers FCCP and DNP. The results are discussed in terms of a concept assuming that the ATP/ADP-antiporter facilitates the electrophoretic export of hydrophobic anions from mitochondria.