Nitrogenase reactivity: cyanide as substrate and inhibitor

We have examined the reduction of cyanide by using the purified component proteins of nitrogenase (Av1 and Av2). The previously reported self-inhibition phenomenon was found to be an artifact. One of the two species present in cyanide solutions, CN-, was shown to be a potent reversible inhibitor (Ki = 27 microM) of total electron flow, apparently uncoupling MgATP hydrolysis and electron transfer. There appears to be no differential effect of CN- on the specific activities of Av1 and Av2 nor is there any apparent irreversible physical damage to Av2. CN- inhibition is completely reversed by low levels of CO, implying a common binding site. Azide partially relieves the inhibitory effect, but other substrates and inhibitors (N2, C2H2, N2O, H2) have no effect. The other species present in cyanide solutions, HCN, was shown to be the substrate (Km = 4.5 mM at Av2/Av1 = 8), and extrapolation of the data indicates that at high enough HCN concentration H2 evolution can be eliminated. The products are methane plus ammonia (six electrons), and methylamine (four electrons). There is an excess (relative to methane) of ammonia formed, which, according to electron balance studies, may arise from a two-electron intermediate. Both nitrous oxide and acetylene (but not N2) influence the distribution of cyanide reduction products, implying simultaneous binding. HCN appears to bind to and be reduced at an enzyme state more oxidized than the one responsible for either H2 evolution or N2 reduction.

Steroid hormone receptors in the rat mammary adenocarcinoma induced by N-hydroxy-N-2-fluorenylacetamide

The steroid hormone receptors in N-2-fluorenylacetamide (2-FAA)- and N-hydroxy-2-FAA-induced mammary adenocarcinomas in outbred Sprague-Dawley rats were analyzed. Both 8S and 4S estrogen-binding components have been detected in cytosols of these tumors following sucrose gradient sedimentation in low salt. Competitive binding analyses of this binder indicated a specificity profile expected of an estrogen receptor. Both androgen and progesterone receptors were also present in the cytosols of these mammary tumors. While the androgen receptor sedimented in the 8S region of the gradient, the progestin binder appeared only as a 4S moiety under similar conditions. The relative concentrations of these receptors (expressed in fmol/mg protein +/- SE) were: 17 beta-estradiol (28.6 +/- 4.1) greater than 5 alpha-dihydrotestosterone (8.5 +/- 2.2) greater than progesterone (5.0 +/- 1.3). The progesterone receptor was increased at least eightfold in the mammary adenocarcinomas from ovariectomized rats that were treated with diethylstilbestrol for 6 days. Binding equilibrium data indicated Ka = 1.2-1.8 X 10(9) M-1 for the above cytoplasmic hormone receptor complexes (Ka, association constant). Although cytosols prepared from lactating mammary gland contained appreciable quantities of glucocorticoid receptor, only trace amounts were found in the mammary adenocarcinoma.

The biology of SAA: identification of the inducer, in vitro synthesis, and heterogeneity demonstrated with monoclonal antibodies

Continued studies of the macrophage-derived mediator of SAA synthesis (SAA Stimulating Factor) confirm our previous observations that SAASF copurified with leukocytic pyrogen (LP) and lymphocyte activating factor (LAF). Moreover, new data demonstrate three separate isoelectric points for human LP-LAF-SAASF each of which possess the three biological activities. During the purification of 15,000 MW LP from crude stimulated mononuclear cell supernatants, only those fractions with pyrogenic activity in rabbits caused augmented stimulation of lymphocytes (LAF) and induced SAA synthesis in mice. Purified human LP stimulated isolated mouse hepatocytes in vitro to synthesize SAA in a dose-responsive manner. Colchicine treatment of hepatocytes led to decreased secretion of SAA into the medium and to an intracellular accumulation of SAA. Messenger RNA was isolated from the livers of endotoxin-stimulated mice and translated in a wheat-germ cell-free system. A major product was identified at 13-14,000 MW. Immunoprecipitation with anti-mouse AA identified several bands on autoradiography of polyacrylamide gels. These larger SAA precursors may account for the previously noted heterogeneity of human SAA, comprising at least 6 SAA isomers, of similar molecular weight but different solubility and electrophoretic charge characteristics. Two monoclonal antibodies (IgM-K and IgG1-K) have been prepared using standard cell hybridization techniques. They are directed at the variable COOH terminal region of SAA since they detect differences between the 6 human SAAs but do not react with human, monkey, dog or mouse AA proteins, human AP, C-reactive protein, IgG nor albumin. These antibodies will be useful in examining the origin, structure and function of SAA.

Properties of the N gene transcription antitermination protein of bacteriophage lambda

The product of the N gene of bacteriophage lambda prevents the termination of lambda early transcription. Here we describe the physical properties of pure lambda N protein. N protein is small and very basic. The apparent Mr of N protein during electrophoresis in the presence of sodium dodecyl sulfate is 12,500. It contains 22 mol % (arginine plus lysine) and only one methionine. The methionine residue is at the blocked NH2 terminal since N protein is not detectably shortened by reaction with cyanogen bromide. When use is made of the DNA sequence of the N gene region of lambda DNA (Franklin, N. C., and Bennett, G. N. (1979) Gene 8, 107-119), the lack of an internal methionine residue, the size, and the amino acid composition of N protein can be used to predict that N protein contains 107 amino acids (calculated Mr = 12,241) and that its coding sequence begins at position 223 of the lambda pL operon mRNA. N protein can be assayed by its ability to stimulate endolysin synthesis in vitro in a reaction programmed with lambda N- DNA. N protein activity is heat-stable and trypsin-sensitive. Its sedimentation velocity in a sucrose gradient and its Stokes' radius indicate that N protein is an extremely asymmetric monomer (f/fmin = 1.6). The relationship between this high degree of molecular asymmetry and the sequence which N protein must recognize in lambda nucleic acid is discussed.

Formation of crystalline arrays of chlorophyll a/b - light-harvesting protein by membrane reconstitution

The structure of the major protein constituent of photosynthetic membranes in higher plants, the chlorophyll a/b-light harvesting complex (LHC), was studied by x-ray diffraction and electron microscopy. The LHC was purified from Triton X-100 solubilized thylakoid membranes of the pea, and contained 6 mol of chlorophylls a and b per mole of a polypeptide of 27,000 molecular weight. X-ray diffraction showed that in the presence of 10 mM MgCl2, purified LHC forms planar aggregates that stack with a period of 51 A. Within each layer, LHC molecules pack with a center-to-center distance of 85 A but without long-range order. However, when LHC is incorporated into single-walled vesicles of plant lecithin, the addition of NaCl above 10 mM, or MgCl2 above 2 mM, led to the formation of plaques of hexagonal lattices, with a lattice constant of 125 A. The large domain size and high degree of order in the plane of the membrane are evident from the sharp lattice lines observed to 7 A resolution on the equator of the x-ray pattern. Freeze-fracture electron micrographs demonstrated an aligned stacking of the lattices in adjacent membranes, resulting in crystallinity in the third dimension over short distances. Micrographs of negatively stained membranes revealed a hexagonal lattice of the same lattice constant, formed by surface-exposed parts of the LHC molecules which are probably responsible for the ordered stacking of lattices. In both the LHC aggregates and in the reconstituted membrane lattices the diffracted x-ray intensities at 10-A spacing on the equator indicate that the LHC molecule contains paralled alpha-helices or beta-sheets that are oriented perpendicular to the planar arrays.

Characterization of specific glucocorticoid receptor in the Syrian hamster testis

Cytosols of whole testicular homogenates from the Syrian golden hamster contained specific binding sites for [3H]triamcinolone acetonide that exhibited limited capacity and high affinity binding characteristic of glucocorticoid receptors in other target tissues. The receptor complex sedimented as an 8.6S binder in low salt 5-20% linear sucrose gradients and as 6.2S and 4.0S moieties in 0.15M and 0.4 M KCl, respectively. The Ka at equilibrium was 3.1-3.3 X 10(9) M-1 at 4 C in intact and adrenalectomized males. The testicular glucocorticoid binder was vulnerable to proteolytic degradation while being completely resistant to the action of RNase and DNase. In addition the binding protein exhibited the usual steroid specificities for type I glucocorticoid receptor: triamcinolone acetonide greater than dexamethasone greater than cortisol greater than corticosterone greater than progesterone greater than aldosterone greater than prednisone greater than 5 alpha-dihydrotestosterone greater than diethylstilbestrol. Unexpectedly, 17 beta-estradiol competed for receptor binding to the same extent as prednisone. A 3.2 S nuclear receptor was extracted from purified testicular nuclei after incubation of whole suspensions in culture media containing 5 nm radiolabeled triamcinolone acetonide at 32 C. Although the glucocorticoid receptor concentrations in prepubertal, adrenalectomized, and hypophysectomized animals were markedly higher in the testis compared to the concentration in the normal adult hamster (52 +/- 4 fmol/mg cytosol protein), the greatest total amount of receptor per testis was found in the mature intact animal. Moreover, under the conditions studied, the concentration of glucocorticoid receptor substantially exceeded the levels of either androgen or estrogen receptor when determined simultaneously. In contrast, no measurable cytoplasmic [3H]triamcinolone acetonide binding was detected in adjacent urogenital organs such as the epididymis and seminal vesicle. It is therefore unlikely that the testicular glucocorticoid receptor is associated with the spermatid or present as a secretory product in the seminiferous tubule lumen.

Interaction of the sigma factor and the nusA gene protein of E. coli with RNA polymerase in the initiation-termination cycle of transcription

The nusA gene protein of E. coli is involved in regulating termination of transcription in vivo. In vitro it causes termination of transcription in the tR2 region of the PR operon of bacteriophage lambda. We have now used a nusA-Sepharose affinity column and gradient sedimentation experiments to show that the nusA protein binds directly, with great specificity, and with equimolar stoichiometry to the E. coli RNA polymerase core enzyme beta beta' alpha 2. The RNA polymerase sigma subunit is able to displace the nusA protein from a beta beta' alpha 2-nusA complex, regenerating RNA polymerase holoenzyme beta beta alpha 2-sigma able selectively to initiate transcription at promoter sites. It is proposed that beta beta' alpha 2-nusA and beta beta' alpha 2-sigma are complementary forms of RNA polymerase that interchange with one another in the initiation-termination cycle of transcription.

Maternal behavior, pup vocalizations, and pup temperature changes following handling in mice of 2 inbred strains

A cross-fostering design was used to examine maternal behavior, pup vocalizations, and pup temperature changes following an infantile procedure in C57BL/6J (C) and A/J (A) mice. In Experiment I, maternal behavior of C and A mothers after infantile handling differed in a number of ways irrespective of the strain of the foster pups. In addition, A pups were retrieved faster but licked less than were C pups by mothers of both strains. Handling appeared to increase the probability that strain differences would occur in that no differences between the lines, in either the behavior of the mothers or the capacity of the pups to elicit maternal behavior, were found during observations made just prior to daily handling. These observations also revealed that mothers of both strains treated same-strain foster pups differently than they treated foster pups of another strain. In Experiment II, A pups were found to emit more ultrasound following handling than were C pups, suggesting that retrieval but not pup-licking was stimulated by ultrasonic signals. Measurement of pup temperature during and following the handling procedure showed that (1) strain differences in ultrasonic signaling were not related to strain differences in the degree of hypothermia experienced by the pups; (2) recovery of body temperature following handling was slow for pups of both strains, and depended to some degree on the strain of the pups' foster mother; and (3) development of thermoregulation occurred more rapidly in C than A pups.

The nonspecificity of diffuse pulmonary uptake of 67Ga on 24-hour images

Eighteen patients who underwent whole-body scintigraphy 24 and 48 hours after intravenous injection of 67Ga-citrate were evaluated retrospectively. At 24 hours, 7 of the 16 normal patients (44%) and both abnormal patients demonstrated significant pulmonary uptake. However, by 48 hours, only 2 normal patients (12%) remained positive, while both abnormal patients continued to show significant pulmonary activity. The authors conclude that 48-hour 67Ga images offer improved specificity and uncompromised sensitivty in patients with diffuse pulmonary disease.

L factor that is required for beta-galactosidase synthesis is the nusA gene product involved in transcription termination

The DNA-dependent in vitro synthesis of Escherichia coli beta-galactosidase requires the presence of a soluble protein referred to as L factor [Kung, H., Spears, C. & Weissbach, H. (1975) J. Biol. Chem. 250, 1556-1562]. In the present study, comparison of physical, immunological, and biological properties shows that L factor is the product of the E. coli nusA gene. The nusA gene product is known to interact with bacteriophage lambda N gene protein and to prevent premature termination of transcription from the early lambda promoters. Our results suggest that premature transcription termination in the lac operon of E. coli may also be overcome by the nusA protein.

Role of self carriers in the immune response and tolerance. V. Reversal of trinitrophenyl-modified self suppression of the B-cell response by blocking of H-2 antigens

Trinitrophenylated syngeneic spleen cells (TNP-SC) are potent tolerogens of the anti-TNP plaque-forming cell (PFC) response in vivo and in vitro. This unresponsive state requires T cells for both its induction and maintenance. Because H-2K/D-restricted cytotoxic T cells are also induced by exposure to TNP-SC, we determined the role(s) of histocompatibility antigens (K, I, and D) in the suppression of the PFC response by TNP-SC. We treated syngeneic TNP-modified stimulator cells with antiserum directed at K-, I-, or D-region determinants and found that blocking of H-2K or D antigens on TNP-SC transformed these tolerogens into immunogens capable of eliciting an anti-TNP PFC response in the absence of extrinsic immunogens like TNP-polymerized flagellin. In H-2k or H-2a(k/d) mice, only H-2Kk needs to be blocked on the stimulator cells, whereas H-2K or D recognition was apparent in B10.A(4R) mice. These observations indicate that suppression of the PFC response by TNP-SC shows the same restriction in recognition as does the cytotoxic T-cell response. Furthermore, our results suggest that TNP-I-A is recognized by the helper cells in this system as the intrinsic antigen. When both TNP-K and TNP-I-A are present and available on the same stimulator cell, suppression (via modified K recognition) is dominant over help.

Infant responsiveness to maternal cues in mice of 2 inbred lines

The present study examined the responsiveness of 19- and 20-day-old C57BL/6J (C) and A/J (A) mouse pups to maternal cues. The C pups were found to spend more time near their C or A foster mother than they did near a virgin female. The A pups showed no such preference. Attempts to increase the motivation of A pups to approach the mother did not produce any preference for maternal cues, However, when the bedding on which odorous substances had been permitted to accumulate for an extended period of time was used as choice stimuli, pups of both lines showed a preference for the bedding of the mother as opposed to that of a virgin female. These results support findings with other rodents of a change in the female's odor during lactation which increases her attractiveness to her pups; and they demonstrate a genetic difference between pups of 2 inbred strains in their approach to maternal cues.

Nuclear retention of all steroid hormone receptor classes in the hamster renal carcinoma

The estrogen-induced hamster renal carcinoma contains appreciable amounts of all cytosolic steroid receptor classes sedimenting as 7 to 8S moieties following sucrose gradient centrifugation. Their relative concentrations, expressed in fmol/mg protein +/- S.E. are progesterone (1496 +/- 23) greater than estradiol (218 +/- 3) greater than 5 alpha-dihydrotestosterone (154 +/- 7) greater than dexamethasone (138 +/- 3) greater than aldosterone (40 +/- 2). No cross-competition is apparent for either estrogen or progesterone receptors, but progesterone competes for both androgen and adrenocorticoid binding. These hormone-receptor complexes undergo nuclear translocation using purified tumor nuclei and in tissue minces at elevated temperatures. Salt-extractable nuclear receptors for estrogen (5S), androgen (3.2S), progesterone (2.7S), and corticosteroid (3.5S) have been identified. The existence of five specific steroid receptors within a single tissue is unique and provides a novel model for studying the interrelated actions of all steroid hormones and their therapeutic responses in a hormone-dependent neoplasm.

Tumoristatic effects of nonimmune BALB/c peritoneal macrophages on syngeneic lymphoma cells in vitro

Peritoneal macrophages from unstimulated nonimmune BALB/c mice exerted nonspecific cytostatic effects of tumor cells in vitro. Incubation of syngeneic B40 lymphoma or allogeneic B16 melanoma cells with peritoneal macrophages or with macrophage culture supernatant fluids (SF) resulted in decreased target cell DNA synthesis and growth; in contrast, nontumorigenic syngeneic 3T3 fibroblasts were stimulated by macrophages but SF exerted no significant effects. Lipopolysaccharide activation of macrophages did not induce cytotoxicity for any target cell tested, and did not enhance the observed tumoristatic effects. The level of tumor inhibition associated with macrophage culture SF was dependent upon the concentration of fetal calf serum present in the medium as well as upon the numbers of macrophages cultured. Inhibitory SF could be harvested continuously from macrophage cultures for at least 7 days with no appreciable loss of activity.

Receptor characteristics of specific estrogen binding in the renal adenocarcinoma of the golden hamster

Linear sucrose gradient analyses reveal that all estrogen-induced and -dependent primary renal tumor cytosols examined contain an 8 S and variable amounts of 4 S receptor in low ionic buffer concentrations. Similar results were obtained with extracts of primary metastases of these tumors. Sucrose gradients containing high salt (0.4 M KCl) convert the 8 S receptor in both the hamster renal tumor and uterus to a 4 to 5 S complex. Scatchard plot analysis reveals that the renal tumor cytosol estradiol-receptor complex has a Ka of 1.7 X 10(9) M-1 and 9.2 X 10(-10) M binding sites. Competition for the tritiated 17beta-estradiol binding sites in the renal tumor was similar to that in the uterus with respect to estrogenic compounds. Nonestrogenic steroids exhibited minimal competition at the same concentrations or higher. Substitution in the ring structure, particularly in position 3 of the phenolic A-ring, resulted in a considerable loss in the ability of such compounds to compete for these receptors. Aniestrogens were effective competitors for these estrogen receptors only at higher concentrations relative to the tritiated estradiol.

Colorectal schistosomiasis: report of three cases

The facility for mass movement of segments of our world populations creates the need for physicians to recognize and manage diseases not seen in native patients. Such a need has occurred in New York City, where schistosomiasis, with its protean manifestations has been seen with increasing frequency. The cases of three patients who had different clinical manifestations of infestation by S. mansoni are presented. Clinical, radiologic, and pathologic features are discussed. To avoid delay in treatment, physicians must consider the possibility of this disorder in cases of patients from areas of endemic schistosomiasis.

Biochemical comparison of estrogen receptors of the hamster hypothalamus and uterus

Comparison of the soluble estradiol receptor proteins in the hypothalamus and uterus of the golden Syrian hamster revealed that both have sedimentation coefficients of 8S in a low ionic strength buffer and migrate similarly on analytical disc-gel electrophoresis in both 5% and 7% acrylamide gels. The competition of [3H]-17beta-estradiol binding by unlabeled estrogenic as well as nonestrogenic compounds was similar with the receptors present in the two tissues. The affinity constants for the hypothalamic and uterine receptors were 4.3 X 10-9M-1 and 1.6 X 10-10M-1, respectively; the number of binding sites when expressed on an equivalent protein basis (i.e. 1 mg/ml) was 0.18 X 10-10M and 3.1 X 10-10M, respectively. Identical amounts of soluble receptors with similar sedimentation characteristics were found in hypothalami from male and female animals gonadectomized 64 h prior to use. A titration of binding sites in the uteri of intact and ovariectomized animals revealed decreased binding in the supernatant preparation from intact animals, probably due to the presence of bound endogenous unlabeled hormone.

Nicotinamide adenine dinucleotide phosphate-malic enzyme of rat liver. Purification, properties, and immunochemical studies

Rat liver malic enzyme (EC 1.1.1.40) was purified from livers of rats fasted and refed a high sucrose diet containing 1% desiccated thyroid powder. The purification was accomplished by a six-step procedure. The specific activity of the purified enzyme was increased 181-fold above that of the initial high speed supernatant of liver extracts. Slight additional purification of malic enzyme was achieved with preparative disc electrophoresis. The specific activities of the purified rat liver malic enzyme from the least two steps were between 28.0 and 30.5 units per mg of protein. Homogeneity of the purified enzyme was determined by disc and starch gel electrophoresis as well as sedimentation velocity and sedimentation equilibrium studies. The molecular weight and S20, w values of rat liver malic enzyme are 268,000 and 10.2, respectively. Amino acid analysis based on milligram of protein hydrolyzed yielded higher amounts of leucine and glutamic acid but lower quantities of alanine and voline per subunit than the corresponding Escherichia coli enzyme...

Junctional specialization in estrogen-induced renal adenocarcinomas of the golden hamster

Estrogen-dependent renal adenocarcinoma and normal proximal tubules of the hamster kidney exhibit junctional differences. Although both cell types possess gap junctions, the neoplastic cells have in addition a cytoplasmic configuration of gap-junctional membrane (annular nexuses) not found in the kidneys of untreated or estrogenized hamsters or in the nontumorous kidney adjacent to the adenocarcinoma. The presence of these unique structures in the renal tumor and its abdominal metastases was demonstrated by electron microscopy with the use of lanthanum impregnation. A possible correlation between these structures and the estrogen sensitivity of the kidney neoplasm is made.

Sex difference and gonadal hormone influence on Syrian hamster kidney esterase isozymes

Thirteen esterase isozymes were separated from kidney extracts of normal adult Syrian hamsters ( Mesocricetus auratus) using the zymogram technique with vertical starch gel electrophoresis and naphthyl esters as substrates. The activities of two esterases were altered by gonadectomy and by treatment with testosterone or estradiol-17β but not with progesterone. One of these esterases showed negligible activity in castrated males and in normal and spayed females. The activity of this esterase increased appreciably in castrated males treated with testosterone or estradiol and in testosterone-treated spayed females. This enhanced activity, however, was not consistent in spayed females treated with estradiol. No sex differences in renal esterases were observed in immature hamsters but a variation was detected in normal adults. The difference appears to be of normal enzyme levels rather than the absence of any esterase. Under the influence of estradiol and progesterone, separately or in combination, distinct alterations in kidney esterase profiles were observed. Certain other quantitative hormonal effects were found. These hormone-dependent esterases do not appear to be cholinesterases, as they were unaffected by eserine. The marked sensitivity of various hamster kidney esterases to estrogen appears to be a unique response and may be related to the estrogenic induction of renal adenocarcinoma, initiated under similar conditions, but not found with androgen-treated or other estrogenized animals. These findings indicate that gonadal effects on the hamster kidney may be of a more complex nature than has been considered heretofore.