Effects of nucleotides on ATP-dependent protein translocation into Escherichia coli membrane vesicles

We have shown previously that Escherichia coli can translocate the same protein either co- or posttranslationally and that ATP hydrolysis is essential for the posttranslational translocation of the precursors of alkaline phosphatase and OmpA protein into inverted E. coli membrane vesicles. ATP-dependent protein translocation has now been further characterized. In the absence of exogenous Mg2+, dATP, formycin A-5'-triphosphate, ATP-alpha-S, and N1-oxide-ATP could replace ATP, but many other nucleotides were not only ineffective but inhibited ATP-dependent translocation. The inhibitors included nonhydrolyzable ATP analogs, ATP-gamma-S, 8-azido-ATP, AMP, ADP, cyclic AMP, PPi, and tripolyphosphate. On the other hand, adenosine, adenosine 5'-tetraphosphate, and N1,N6-etheno-ATP neither supported nor inhibited translocation. Moreover, photoaffinity labeling of azido-adenine nucleotides rendered membranes inactive for subsequent ATP-dependent protein translocation. These results suggest that protein translocation involves at least an ATP-binding site in the membrane and hydrolysis of ATP and that both the adenosine and phosphate moieties of ATP play a role.

Effect of tolazamide on basal ketogenesis, glycogenesis, and gluconeogenesis in liver obtained from normal and diabetic rats

The effect of tolazamide on in vitro rates of gluconeogenesis, ketogenesis, and glycogenesis was determined in liver tissue from fasted normal and diabetic rats. Hormones were not added to the incubation mixture. Two concentrations of the drug were tested, one of which was therapeutic (40 micrograms/ml) and other immoderately elevated (400 micrograms/ml). Neither drug concentration affected hepatic glycogen synthesis. However, the low dose of tolazamide inhibited ketogenesis in the diabetic liver by 39% and in the control liver by 32%; oxidative CO2 production from palmitate was reduced in parallel with ketogenesis. The drug did not alter ketogenesis in isolated intact mitochondria. Similarly, this same therapeutic dose curtailed hepatic gluconeogenesis only in control liver (74% inhibition); this reaction was unaltered by this drug concentration in the explants derived from the diabetic rats. The logarithmically higher dose inhibited hepatic gluconeogenesis in both control and diabetic liver tissue by 56% and 51%, respectively. Hence, possibly acting at a postreceptor site, therapeutic concentrations of tolazamide can decrease rat hepatic in vitro gluconeogenesis and ketogenesis.

A successful replantation of rat ear

This article presents a successful replantation of a completely severed rat ear. The procedure include re-union of the tubal cartilage and anastomosis of the surgically divided external carotid artery and posterior facial vein.

Influence of isoflurane on hypoxic pulmonary vasoconstriction in dogs

The authors studied the influence of locally administered isoflurane anesthesia on the pulmonary vascular response to regional alveolar hypoxia (hypoxic pulmonary vasoconstriction [HPV]) over a range of cardiac outputs (COs) in seven mechanically ventilated, closed-chest dogs. The right lung was ventilated with 100% O2 throughout the study. The left lung was ventilated with either 100% O2 (normoxia) or an hypoxic gas mixture (hypoxia). Different alveolar concentrations of isoflurane (0, 1, and 2.5 MAC) were administered to the left lung in a randomized sequence. The CO was altered by opening and closing surgically produced arteriovenous fistulae, at all isoflurane concentrations, and by hemorrhage at 0 MAC isoflurane. The magnitude of the HPV response was measured by differential CO2 elimination in the absence of isoflurane and by venous admixtures in all phases. During normoxia, the left lung effective flow (QL%) measured from differential CO2 excretion was 39.9 +/- 1.2% of the total blood flow and decreased to 18.8 +/- 2.6% when ventilated with the hypoxic gas mixture. Venous admixture (QVA/QT%) was significantly correlated with QL% during hypoxic ventilation in the absence of isoflurane. QVA/QT% was 22.3 +/- 2.7% during hypoxia with normal CO, and it increased significantly to 27.7 +/- 1.1% when the CO was increased 43%. It was not significantly altered (23.6 +/- 3.6%) when the CO was decreased by 54%. Isoflurane 2.5 MAC significantly increased QVA/QT% during hypoxic ventilation of the left lung to 33.9 +/- 2.6% with low CO and 35.4 +/- 1.7% with normal CO. Isoflurane 1 MAC increased QVA/QT% to 27.2 +/- 2.7% with normal CO and 28.1 +/- 2.6% with high CO.(ABSTRACT TRUNCATED AT 250 WORDS)

Spiral interrupted suturing technique for microvascular anastomosis: a comparative study

This is an experimental study comparing the suturing time and patency rate of a spiral interrupted suturing technique to those of conventional interrupted and continuous suturing technique in end-to-end as well as end-to-side anastomosis. The spiral interrupted suturing technique requires less time for either end-to-end or end-to-side anastomosis than conventional interrupted suturing technique, and does not result in stenosis as shown in the venous end-to-end anastomosis by continuous suturing technique.

Meningioma in the anterior III ventricle in a child

A case is described of meningioma in the anterior part of the III ventricle in a 14-year-old girl. The mass was successfully removed through a transcallosal approach.

Hypoxic pulmonary vasoconstriction is not potentiated by repeated intermittent hypoxia in closed chest dogs

Hypoxic pulmonary vasoconstrictor (HPV) responses were measured with repeated intermittent hypoxic challenges in eight non-traumatized closed chest dogs anesthetized with pentobarbital. The right lung was ventilated continuously with 100% O2 while the left lung was either ventilated with 100% O2 (control) or ventilated with a gas mixture containing 3-4% O2 (hypoxia). Mean per cent left lung blood flow for all four normoxic periods was 43.1 +/- 1.5% (mean +/- SE) of the total blood flow by the SF6 excretion method and 40.8 +/- 1.1% by the differential CO2 excretion method, corrected for the Haldane effect. With hypoxic ventilation, flow diversion from the hypoxic lung was maximal with the first exposure and did not change subsequently with a total of four alternating exposures to normoxia and hypoxia. Flow diversion during hypoxia was approximately 50.5 +/- 2.4% by the SF6 method and 50.3 +/- 3.5% by the VCO2 method. This result contrasts with the increasing flow diversion response with intermittant hypoxic exposure that has been reported in animals exposed first to thoracotomy and surgical dissection. It is concluded that in the absence of surgical trauma the initial response to hypoxia is maximal and is not potentiated by repeated hypoxic stimulation.

[A simple method for performing yeast carbohydrate assimilation test]

A modified auxanographic method was employed to perform carbohydrates assimilation test for 25 strains of yeasts representing the following 8 species: Candida albicans, C. glabrata, C. krusei, C. parapsilosis, C. stellatoides, C. tropicalis, Cryptococcus neoformans, and Rhodotorula glutinis. The results obtained were analyzed by comparing with the conventional auxanographic method, and it was found that the modified method was more accurate, rapid and easy in reading. The modified method was obviously easier in manipulation and more economic than that of Wickerham's broth technique and yeast assimilation agar slant technique.

ATP is essential for protein translocation into Escherichia coli membrane vesicles

The energy requirement for translocation of alkaline phosphatase and the outer membrane protein OmpA into Escherichia coli membrane vesicles was studied under conditions that permit posttranslational translocation and, hence, prior removal of various components necessary for protein synthesis. Translocation could be supported by an ATP-generating system or, less well, by the protonmotive force generated by D-lactate oxidation; the latter might act by generating ATP from residual bound nucleotides. However, when protonmotive force inhibitors were used or when ATP was further depleted by E. coli glycerol kinase, D-lactate no longer supported the translocation. Furthermore, ATP could still support protein translocation in the presence of proton uncouplers or with membranes defective in the F1 fraction of the H+-ATPase. We conclude that ATP is required for protein translocation in this posttranslational system (and probably also in cotranslational translocation); the protonmotive force may contribute but does not appear to be essential.

Topological structure in the perception of apparent motion

Not only translations and rotations, but also intriguing 'plastic deformations' are observed in apparent motion. What kinds of invariants does the visual system depend on during these transformations to determine that two figures of different shapes nevertheless represent the same object? Experiments are reported in which seven pairs of stimuli with topological differences were used. The evidence suggests that topological invariants may be used in the perception of apparent motion. In spite of variations in other factors, such as brightness, spatial frequency, terminators, etc, subjects displayed a strong preference for motion from a central figure to a figure with the same topological invariants. The results emphasize the importance of topological structure in figure perception.

Alkaline phosphatase and OmpA protein can be translocated posttranslationally into membrane vesicles of Escherichia coli

We previously described a system for translocating the periplasmic enzyme alkaline phosphatase and the outer membrane protein OmpA into inverted membrane vesicles of Escherichia coli. We have now optimized and substantially improved the translocation system by including polyamines and by reducing the amount of membrane used. Under these conditions, efficient translocation was seen even posttranslationally, i.e., when vesicles were not added until after protein synthesis was stopped. This was the case not only with the OmpA protein, which is synthesized by free polysomes and hence is presumably exported posttranslationally in the cell, but also with alkaline phosphatase, which is synthesized only by membrane-bound polysomes and has been shown to be secreted cotranslationally in the cells. Prolonged incubation rendered the precursors inactive for subsequent translocation. Posttranslational translocation was impaired, like cotranslational translocation, by inhibitors of the proton motive force and by treatment of the vesicles with protease. Since it appears that E. coli can translocate the same proteins either cotranslationally or posttranslationally, the cotranslational mode may perhaps be more efficient, but not obligatory, for the secretion of bacterial proteins.

The influence of halothane and isoflurane on pulmonary collateral ventilation

The effects of halothane and isoflurane on hypocapnic increases in pulmonary collateral resistance were studied in dogs. A bronchoscope with a double lumen catheter in the suction port obstructed a peripheral airway and allowed gas to flow out of the isolated segment of lung only via collateral channels. The collateral gas flow (Vcoll) was measured with a flowmeter and delivered through one lumen of the catheter, while the other lumen measured distal pressure (Pb). At FRC, the resistance to collateral ventilation (Rcoll) was calculated as Rcoll = Pb/Vcoll. The rest of the lung was ventilated with air, while air (hypocapnia), 10% CO2 in air, or air and halothane or isoflurane were delivered to the isolated segment. A measurement of resistance was made after 4 min of test gas flow. For each segment, when air replaced 10% CO2, the average increase in Rcoll was calculated and called Rmax. When 10% CO2 in air was infused into segments the mean Rcoll (n = 50) was 0.0196 +/- 0.0022 cmH2O X ml-1 X min. This increased to 0.0285 +/- 0.0031 cmH2O X ml-1 X min (mean +/- E) when air was infused, a mean increase in resistance of 52 +/- 3%. When halothane or isoflurane was added to air the hypocapnic increase in Rcoll was attenuated with a 50% decrease at 1.3% (1.4 MAC and 0.8 MAC, respectively). These two inhalational anesthetics reduce active changes in the flow resistance to collateral ventilation. When collateral resistance acts to adjust ventilation perfusion deviations, this action of halothane and isoflurane may make this regulation less effective.

Cell to cell transmission of the "priming" effect on the induction of human fibroblast interferon

Human fibroblast cells remain primed for IFN-beta 1 synthesis for at least 18 days after the removal of IFN-beta 1, to the same extent as cells primed shortly before induction. The maximal effect of priming is observed in cells that are treated with IFN at low cell density and are subsequently allowed to undergo several divisions. This observation suggests that the information for priming is propagated from cell to cell upon cell division. A diminished priming effect is observed after cells undergo more than three divisions in culture, suggesting a dilution of the mediator responsible for the transmission of the effect. It was not possible to demonstrate intercellular communication of the priming effect by a mediator found in the medium or by cell to cell contact. Observation that priming persists in cells for 18 days in the absence of detectable levels of IFN in the medium, but virus-resistance declines after three days supports the previous suggestion for different mechanisms involved in these two IFN-induced phenomena.

A human IFN-beta 1 gene deleted of promoter sequences upstream from the TATA box is controlled post-transcriptionally by dsRNA

Induction of IFN-beta 1 RNA was studied in the mouse cell line SR117-21E transformed by a BPV episome containing the human IFN-beta 1 gene deleted of promoter sequences upstream from position -40. Nuclei isolated from these cells synthesize constitutively IFN-beta 1 RNA from the partially deleted promoter. The IFN-beta 1 RNA synthesized by nuclei of uninduced SR117-21E cells is similar to that made by nuclei of poly(rI):(rC)-induced cells, but does not accumulate and hence no IFN is produced unless the cells have been treated either by ds RNA or by cycloheximide. We conclude that the IFN-beta 1 gene has, in addition to the transcription control due to upstream promoter sequences, an additional post-transcriptional control acting on mRNA accumulation and linked to sequences close to the TATA box and RNA start site. Both controls are relieved by ds RNA.

Efficient constitutive production of human fibroblast interferon by hamster cells transformed with the IFN-beta 1 gene fused to an SV40 early promoter

The coding sequence of the human interferon (IFN)-beta 1 gene, fused 60 bp downstream from the RNA start site of the SV40 early gene, was transfected into dihydrofolate reductase (DHFR)-deficient Chinese hamster ovary (CHO) cells together with a selectable DHFR gene. Most transformants continuously secreted IFN-beta 1 into the medium. Induction did not stimulate expression of the fused SV40-IFN-beta 1 gene. The role of the SV40 promoter was verified by transforming cells with the unmodified human IFN-beta 1 gene, or by the IFN-beta 1 coding region fused to another poly(rI):(rC)-inducible gene. In these cases, the transformants showed strictly inducible (not constitutive) IFN secretion. By selection for methotrexate resistance, CHO clones with a 10-20-fold amplification of the SV40-IFN-beta 1 DNA were obtained. Such clones constitutively produce up to 350,000 units IFN/ml per 10(6) cells/24 hr, i.e., over 10 times more than fully induced human fibroblasts. In continuous culture with daily changes of medium, accumulation of IFN-beta 1 is constant at a rate of 300,000 molecules per cell/hr. Batches of up to 16 mg of IFN-beta 1 produced by the transformed CHO cells were purified to homogeneity by affinity chromatography on monoclonal antibodies. This IFN appears identical in size, activity, and immunospecificity to the native human IFN-beta 1 glycoprotein.

Time course and responses of sustained hypoxic pulmonary vasoconstriction in the dog

The stability of the pulmonary blood pressure and flow response to alveolar hypoxia (hypoxic pulmonary vasoconstriction or HPV) was studied in six pentobarbital anesthetized, mechanically ventilated open-chested dogs. Aortic and left pulmonary artery blood flows; systemic and pulmonary arterial, central venous, left atrial, and airway pressures; hemoglobin; arterial and mixed venous blood gases were measured. The right lung was ventilated continuously with 100% oxygen, while the left lung was ventilated alternately with 100% O2 ( prehypoxia control phase), an hypoxic gas mixture containing 4% O2, 3% CO2, balance N2 for 4 h, or 100% O2 (post-hypoxia control phase). Hypoxic ventilation of the left lung resulted in an immediate and sustained decrease in left lung blood flow (QL%) from 39.0 +/- 1.8% (mean +/- SE) to 9.9 +/- 3.6% at 15 min of hypoxic ventilation. QL% remained decreased and did not vary significantly during the 4 h of hypoxia. Venous admixture correspondingly was increased and PaO2 decreased by hypoxic ventilation and did not vary significantly during the 4 h of hypoxia. All variables returned to control levels upon reestablishing ventilation with 100% O2. While the maximal reduction in QL% with left lung hypoxic ventilation was identical to that observed during atelectasis previously in our laboratory, the time course of the response was different. The response to hypoxia was maximal by 15 min, however, QL% decreased more slowly during atelectasis, where the maximal reduction was observed by 60 min. The present study therefore demonstrated that hypoxic ventilation of the left lung yielded an immediate and sustained decrease in left lung blood flow for 4 h. The stability of the HPV response probably was accounted for by the lack of such confounding factors as respiratory alkalosis, severe systemic hypoxemia, and increased cardiac output.

Clinical and immunopathologic study of mesangial IgM nephropathy: report of 41 cases

Forty-one out of 408 cases (or 10%) of primary glomerular disease had diffuse fine granular to arc-like short linear mesangial deposits of IgM by direct immunofluorescence. The IgM deposition was accompanied by C1q and/or C4 in the same locality in 29 cases, by C3 in 10, and by trace amounts of IgA in 6. Properdin-factor B was not detected. Fine granular electron dense deposits of low density were detected in the mesangium in all 41 cases by electron microscopy, usually as a discrete granular or arc-like pattern beneath the mesangial glomerular basement membrane and correlated well with the immunofluorescence findings. An immune complex disease with complement activation via the classical pathway is suggested. The ages of the patients varied from 2 to 58 years (average 23.8 years). A male predominance of 2.2:1 was identified. Serum IgM level was elevated in 46.7% of the cases. The majority (87.8%) of the cases manifested a nephrotic syndrome or relapse at time of biopsy, and the remaining cases experienced persistent or intermittent proteinuria. Among the 36 nephrotic patients, 22 cases (61.1%) demonstrated complete remission with steroid therapy, 9 cases (25%) were resistant, and 5 cases (13.9%) had partial remission. Complete and partial remissions were later achieved with cytotoxic drugs or methylprednisolone pulse therapy in 3 and 4 cases respectively in the steroid resistant patients. Frequent relapses occurred during the course in 22 out of 32 cases (68.8%) who had experienced complete or partial remission. Follow-up study after biopsy demonstrated that sustained complete remission was achieved with prednisolone with or without cytotoxic drugs and pulse therapy in only 14 (42.4%) of the 33 nephrotic cases who had been followed up for longer than 6 months, and six of them had had previous relapses. Pathologically, 56.1% of the patients showed mild to moderate increase in mesangial matrix and cellularity. Focal and segmental sclerosis was demonstrated in four cases (9.8%). However, minimal glomerular change was also common (34.1%). The patients with minimal change seemed to have a higher complete remission rate than patients with more evident glomerular alterations, although the difference was not statistically significant. This clinical and immunopathological study suggests that mesangial IgM nephropathy is an important disease in Taiwan, with a variable response to treatment and frequent relapses.(ABSTRACT TRUNCATED AT 400 WORDS)

Influence of the method of re-expansion of atelectatic lung upon the development of pulmonary edema in dogs

An endobronchial tube was used to separately ventilate each lung in anesthetized dogs, and absorption atelectasis was then induced in the left lung and maintained for 3 1/2 h. The left lung was partially re-expanded by ventilation at normal tidal volumes for 10 min, and then completely re-expanded by manual hyperinflation. This delayed re-expansion was associated with an extravascular water content significantly greater than that of the right lung. A previous study demonstrated no increase in the ratio of left to right lung water content after 3 h of atelectasis alone and a significant increase after immediate hyperinflation. Delayed re-expansion produces significantly different results, and it is therefore concluded that the method of lung re-expansion influences the development of pulmonary edema after atelectasis.

Cycloheximide induces expression of the human interferon beta 1 gene in mouse cells transformed by bovine papillomavirus-interferon beta 1 recombinants

Mouse cells transformed by a bovine papillomavirus recombinant vector containing the human interferon (IFN) beta 1 (IFN-beta 1) gene could be induced to produce human as well as mouse IFNs. The optimal conditions for induction of human IFN and of its mRNA in these transformants resembled those needed for mouse IFN: high concentrations of DEAE-dextran and low concentrations of polyriboinosinic acid-polyribocytidylic acid. Superinduction by inhibitors of protein synthesis which strongly stimulate IFN-beta 1 induction in human cells had only a small effect on human IFN induction in bovine papillomavirus IFN-beta 1-transformed mouse cells. In contrast, cycloheximide without double-stranded RNA could induce significant levels of human IFN in the bovine papillomavirus IFN-beta 1 mouse transformants. After cycloheximide treatment, these cells contained IFN-beta 1 mRNA whose 5' ends originated in the authentic start site of the human IFN-beta 1 gene, as shown by S1 nuclease mapping. The transferred human gene, propagated extrachromosomally in the mouse cells, was, therefore, inducible under conditions different from those in human cells. The results also confirmed that the inhibitor of protein synthesis, cycloheximide, can induce expression of a human IFN gene.

Expression of human interferon genes using the recA promoter of Escherichia coli

Interferon beta 1 and three alpha-interferon genes were cloned on Eco RI fragments isolated from a human genomic library into the Eco RI site of a plasmid containing the recA promoter of E. coli. Expression of interferon activity from cells carrying these plasmids was nalidixic acid inducible. The alpha-interferon genes were expressed only when in the same transcriptional orientation as the recA promoter while the beta 1 interferon gene was expressed in either orientation. Interferon activity was also inducibly expressed from the recA promoter in cells containing a plasmid carrying a fusion of the recA gene with the beta 1 interferon gene. This interferon activity was thirty-fold less sensitive to neutralization by polyclonal antibodies than authentic interferon, implying that the change near the amino terminus affects either antibody recognition or specific activity or both.

Topological structure in visual perception

Three experiments on tachistoscopic perception of visual stimuli demonstrate that the visual system is sensitive to global topological properties. The results indicate that extraction of global topological properties is a basic factor in perceptual organization.