Inhaled nitric oxide reverses pulmonary vasoconstriction in the hypoxic and acidotic newborn lamb

We determined whether inhaling low levels of nitric oxide (NO) gas could selectively reverse hypoxic pulmonary vasoconstriction in the near-term newborn lamb and whether vasodilation would be attenuated by respiratory acidosis. To examine the mechanism of air and NO-induced pulmonary vasodilation soon after birth, we measured plasma and lung cGMP levels in the newly ventilated fetal lamb. Breathing at FIO2 0.10 nearly doubled the pulmonary vascular resistance index in newborn lambs and decreased pulmonary blood flow primarily by reducing left-to-right blood flow through the ductus arteriosus. Inhaling 20 ppm NO at FIO2 0.10 completely reversed hypoxic pulmonary vasoconstriction within minutes. Maximum pulmonary vasodilation occurred during inhalation of > or = 80 ppm NO. Breathing 8% CO2 at FIO2 0.10 elevated the pulmonary vascular resistance index to a level similar to breathing at FIO2 0.10 without added CO2. Respiratory acidosis did not attenuate pulmonary vasodilation by inhaled NO. In none of our studies did inhaling NO produce systemic hypotension or elevate methemoglobin levels. Four minutes after initiating ventilation with air in the fetal lamb lung, cGMP concentration nearly doubled without changing preductal plasma cGMP concentration. Ventilation with 80 ppm NO at FIO2 0.21 increased both lung and preductal plasma cGMP concentration threefold. Our data suggest that inhaled NO gas is a rapid and potent selective vasodilator of the newborn pulmonary circulation with an elevated vascular tone due to hypoxia and respiratory acidosis that acts by increasing lung cGMP concentration.

Inhaled nitric oxide in congenital heart disease

BACKGROUND

Congenital heart lesions may be complicated by pulmonary arterial smooth muscle hyperplasia, hypertrophy, and hypertension. We assessed whether inhaling low levels of nitric oxide (NO), an endothelium-derived relaxing factor, would produce selective pulmonary vasodilation in pediatric patients with congenital heart disease and pulmonary hypertension. We also compared the pulmonary vasodilator potencies of inhaled NO and oxygen in these patients.

METHODS AND RESULTS

In 10 sequentially presenting, spontaneously breathing patients, we determined whether inhaling 20-80 ppm by volume of NO at inspired oxygen concentrations (FIO2) of 0.21-0.3 and 0.9 would reduce the pulmonary vascular resistance index (Rp). We then compared breathing oxygen with inhaling NO. Inhaling 80 ppm NO at FIO2 0.21-0.3 reduced mean pulmonary artery pressure from 48 +/- 19 to 40 +/- 14 mm Hg and Rp from 658 +/- 421 to 491 +/- 417 dyne.sec.cm-5.m-2 (mean +/- SD, both p < 0.05). Increasing the FIO2 to 0.9 without adding NO did not reduce mean pulmonary artery pressure but reduced Rp and increased the ratio of pulmonary to systemic blood flow (Qp/Qs), primarily by increasing Qp (p < 0.05). Breathing 80 ppm NO at FIO2 0.9 reduced mean pulmonary artery pressure and Rp to the lowest levels and increased Qp and Qp/Qs (all p < 0.05). While breathing at FIO2 0.9, inhalation of 40 ppm NO reduced Rp (p < 0.05); the maximum reduction of Rp occurred while breathing 80 ppm NO. Inhaling 80 ppm NO at FIO2 0.21-0.9 did not alter mean aortic pressure or systemic vascular resistance. Methemoglobin levels were unchanged by breathing up to 80 ppm NO for 30 minutes.

CONCLUSIONS

Inhaled NO is a potent and selective pulmonary vasodilator in pediatric patients with congenital heart disease complicated by pulmonary artery hypertension. Inhaling low levels of NO may provide an important and safe means for evaluating the pulmonary vasodilatory capacity of patients with congenital heart disease without producing systemic vasodilation.

Hybridization Between the Western and Northern Call Races of the Limnodynastes-Tasmaniensis Complex (Anura, Myobatrachidae) on the Murray River in South Australia

The Limnodynastes tasmaniensis complex consists of three call races: northern, southern and western. This paper documents differences in call structure between the western and northern races: differences in note repetition rate, dominant frequency, average number of notes per call and pulses per second note, but not in pulse repetition rate. The races also differ in egg size (smaller in northern) and egg number (higher in northern). There are zones of overlap between these two races west from Morgan and along the Marne River in South Australia. Mixed populations contain both parental and hybrid phenotypes. Hybrids were identified by a hybrid index based on the three call components that overlapped least (note repetition rate, dominant frequency and average number of notes per call). Temporary range expansions, associated with flooding on the Murray River, are documented for the northern call race. Artificial hybridisations revealed no evidence of hybrid inviability and this was supported by estimates of egg viability in field-collected egg masses from the Morgan zone of overlap. The hybrid zones are interpreted as zones of overlap with hybridisation where introgression is likely to occur. Biogeographic data suggest that the northern call race may be spreading south and west, displacing the western call race.

Effects of 3'-azido-3'-deoxythymidine metabolites on simian virus 40 origin-dependent replication and heteroduplex repair in HeLa cell extracts

Although the capacity of 3'-azido-3'-deoxythymidine (AZT) triphosphate, an active metabolite of the antiviral agent zidovudine (AZT), to inhibit polymerization by a variety of purified DNA polymerases has been described, it is important to understand its effect on replication by the more complex protein assemblies responsible for DNA replication in human cells. In the present study, we have determined the effects of AZT metabolites on the efficiency of simian virus 40 origin-dependent bidirectional replication of double-stranded DNA in extracts of human HeLa cells. Replication was inhibited by AZT diphosphate and AZT triphosphate, but only at concentrations exceeding those thought to be present in vivo. However, replication was inhibited by AZT monophosphate at concentrations previously reported to accumulate in human cells cultured in the presence of AZT, suggesting that AZT monophosphate may contribute to cytotoxicity by inhibiting chromosomal replication. In an attempt to determine whether AZT treatment could have longer term mutagenic effects on cells, we also determined the effects of these AZT derivatives on replication fidelity and on the efficiency of repair of DNA substrates containing single-base mismatches. Despite the ability of a normal deoxynucleoside monophosphate to reduce the fidelity of DNA replication, presumably by reducing exonucleolytic proofreading of errors, neither the mono-, di-, nor triphosphate form of AZT reduced base substitution fidelity when present in replication reactions. Similarly, the efficiency of repair of DNA substrates containing single-base mismatches was unaffected by these compounds. However, replication fidelity was affected by perturbations in relative and absolute concentrations of deoxynucleoside triphosphate substrates similar to those reported to occur in AZT-treated cells. Thus, AZT treatment could potentially be mutagenic in vivo via reduced replication fidelity resulting from alterations in deoxynucleoside triphosphate pools.

Inhaled nitric oxide in persistent pulmonary hypertension of the newborn

Nitric oxide (NO) has vasodilatory effects on the pulmonary vasculature in adults and animals. We examined the effects on systemic oxygenation and blood pressure of inhaling up to 80 parts per million by volume of NO at FiO2 0.9 for up to 30 minutes by 6 infants with persistent pulmonary hypertension of the newborn (PPHN). In all infants this treatment rapidly and significantly increased preductal oxygen saturation (SpO2); in 5 infants postductal SpO2 and oxygen tensions also increased. Inhalation of NO did not cause systemic hypotension or raise methaemoglobin. These data suggest that low levels of inhaled NO have an important role in the reversal of hypoxaemia due to PPHN.

The role of the nurse in high-quality patient care: a review of the literature

A review of the literature reveals a range of the nurse's subroles within the service of nursing. Competence in psychomotor, cognitive and affective skills is required for performance within each of these subroles to achieve the delivery of high-quality nursing care.

Activation of the trans geometry in platinum antitumor complexes: a survey of the cytotoxicity of trans complexes containing planar ligands in murine L1210 and human tumor panels and studies on their mechanism of action

The cytotoxicity of transplatinum complexes of structural formula trans-[PtCl2(L)(L')] [L = L' = pyridine or thiazole, or L = quinoline (R' = methyl; R" = methyl, phenyl, or CH2phenyl) and L' = R'R"SO] has been studied in murine L1210 and human tumor cell lines. The results confirm previous observations that use of a sterically hindered planar ligand greatly enhances cytotoxicity, in comparison to trans-[PtCl2(NH3)2], such that in some cases cytotoxicity equivalent to that of the clinically used agent cisplatin [cis-[PtCl2(NH3)2]] is obtained. Results from both the panel of human ovarian carcinoma cell lines and the National Cancer Institute screening panel confirm a different pattern of cytotoxicity, with respect to cisplatin. The new trans-platinum complexes are also non-cross-resistant with cisplatin in both murine and human (human ovarian carcinoma panel) tumor cell lines. Preliminary mechanistic studies using both cis- and trans-[PtCl2(pyridine)2] in L1210 cells have been carried out, to delineate the reasons for both the dramatically enhanced cytotoxicity and the lack of cross-resistance with the clinically used agents. Intracellular uptake is enhanced for pyridine relative to ammine (NH3) complexes. The pyridine complexes also inhibit DNA synthesis, implying a role for DNA binding in their mechanism of action. Binding of the pyridine complexes to calf thymus DNA is, however, significantly less than for the analogous ammine complexes. The presence of trans-pyridine ligands results in steric hindrance, which retards the rate of reaction of trans-[PtCl2(pyridine)2], relative to trans[PtCl2(NH3)2], with other important biomolecules such as glutathione. The results point to a potential new class of platinum antitumor complexes acting by a new mechanism and with activity complementary to agents such as cisplatin.

The effects of dNTP pool imbalances on frameshift fidelity during DNA replication

The use of unequal concentrations of the four deoxynucleoside triphosphates (dNTPs) in DNA polymerization reactions alters base substitution error rates in a predictable way. Less is known about the effects of substrate imbalances on base addition and deletion error rates. Thus, we examined pool bias effects on frameshift fidelity during DNA synthesis catalyzed by replicative DNA polymerases. Imbalanced pools altered the frameshift fidelity of the human immunodeficiency virus type-1 reverse transcriptase. Both mutagenic and antimutagenic effects were observed for minus-one, plus-one, and minus-two nucleotide errors, in a highly sequence-specific manner. Most of this specificity can be rationalized by either of two models. One involves frameshifts initiated by pool bias-induced nucleotide misinsertion, and the other involves pool bias-initiated template-primer slippage. Several examples of complex mutations were also recovered more than once in small mutant collections. These contained closely spaced single-base substitution and minus-one base frameshift changes. The two changes occurred at a frequency much higher than predicted if they were generated independently. This suggests that when the polymerase makes one mistake, the probability that it will make a second mistake within the next few incorporations increases significantly. Perturbation of dNTP pools also affected the frameshift fidelity of the replicative yeast DNA polymerase alpha. In reactions containing a low concentration of one dNTP, the error rate increased for one-nucleotide deletions at homopolymeric template nucleotides complementary to the dNTP whose concentration was low. We extended this approach to determine the frameshift fidelity of simian virus 40 origin-dependent semiconservative replication of double-stranded DNA in extracts of human cells. In reactions performed with an equal concentration of all four dNTPs, replication was highly accurate for minus-one-nucleotide errors. However, when the concentration of one dNTP was decreased, the replication error rate increased at complementary, homopolymeric template positions. This response provides an approach for describing frameshift accuracy during replication of the leading and lagging strands.

Effects of clearfelling on stream and soil water aluminium chemistry in three UK forests

Data are presented demonstrating how clearfelling has changed soil and stream water aluminium chemistry. For soil waters, a strong empirical relationship was observed between inorganic aluminium (Al(inorg)) and total inorganic anion (TIA) concentrations. Before felling, chloride and sulphate accounted for the largest proportion of the TIA concentration. After felling, in soils where nitrification was active, nitrate became increasingly important. Where this led to an increase in TIA, Al(inorg) concentrations increased. Over five years, nitrate concentrations have fallen, along with TIA, resulting in a sympathetic decline in Al(inorg). Streams draining clearfelled areas initially became more acid, although chloride and sulphate concentrations decreased. Stream water nitrate concentrations increased soon after felling and remained higher than controls for up to four years. While nitrate concentrations were high, Al(inorg) remained unchanged. Subsequently, as nitrate and TIA decreased, Al(inorg) also declined to concentrations below those in the control stream. Clearfelling upland forests will not necessarily result in immediate improvements in water quality, although long-term benefits may be seen before canopy-closure of the next crop.

Fidelity of mammalian DNA replication and replicative DNA polymerases

Current models suggest that two or more DNA polymerases may be required for high-fidelity semiconservative DNA replication in eukaryotic cells. In the present study, we directly compare the fidelity of SV40 origin-dependent DNA replication in human cell extracts to the fidelity of mammalian DNA polymerases alpha, delta, and epsilon using lacZ alpha of M13mp2 as a reporter gene. Their fidelity, in decreasing order, is replication greater than or equal to pol epsilon greater than pol delta greater than pol alpha. DNA sequence analysis of mutants derived from extract reactions suggests that replication is accurate when considering single-base substitutions, single-base frameshifts, and larger deletions. The exonuclease-containing calf thymus DNA polymerase epsilon is also highly accurate. When high concentrations of deoxynucleoside triphosphates and deoxyguanosine monophosphate are included in the pol epsilon reaction, both base substitution and frameshift error rates increase. This response suggests that exonucleolytic proofreading contributes to the high base substitution and frameshift fidelity. Exonuclease-containing calf thymus DNA polymerase delta, which requires proliferating cell nuclear antigen for efficient synthesis, is significantly less accurate than pol epsilon. In contrast to pol epsilon, pol delta generates errors during synthesis at a relatively modest concentration of deoxynucleoside triphosphates (100 microM), and the error rate did not increase upon addition of adenosine monophosphate. Thus, we are as yet unable to demonstrate that exonucleolytic proofreading contributes to accuracy during synthesis by DNA polymerase delta. The four-subunit DNA polymerase alpha-primase complex from both HeLa cells and calf thymus is the least accurate replicative polymerase. Fidelity is similar whether the enzyme is assayed immediately after purification or after being stored frozen.(ABSTRACT TRUNCATED AT 250 WORDS)

A phase I clinical trial of didemnin B

Didemnin B is a depsipeptide extracted from the marine tunicate Trididemnin cyanophorum. This agent is a potent inhibitor of L1210 growth in vitro and has activity against murine B16 melanoma, P388 leukemia, and M5076 sarcoma in vivo. The results of preclinical toxicologic tests demonstrated abnormalities in clotting parameters thought to be secondary to drug-induced liver dysfunction. Thirty-five patients with advanced cancer received didemnin B according to a 5-day bolus schedule with dose levels ranging from 0.03 to 2.00 mg/m2/d. The dose-limiting toxicity was nausea and vomiting. Sporadic elevation of the hepatic enzyme level occurred but was not dose limiting. Two patients had anaphylactic symptoms possibly related to the 5% polyoxyethylated castor oil (Cremophor EL, BASF, Ludwigshafen, Germany) vehicle during the drug infusion. Clinical bleeding was not observed and myelosuppression was not significant. No partial or complete tumor responses were seen. The recommended Phase II dose for the 5-day schedule is 1.6 mg/m2/d.

An infant and toddler feeding group program

At Children's Medical Center of Dayton, Ohio, several children whose early oral feedings were delayed or especially difficult due to physical problems became resistant and exhibited aversive behaviors when oral feeding was introduced. A support group, which lasted for 9 months, was initiated with six of these children and their families. In the group, professionals provided the families with general information about nutrition and behavior and with individualized intervention strategies for the nutritional and behavioral management of their child's specific problems. The families contributed mutual support and problem solving strategies through the group process. Each child demonstrated progress during the 9-month period, which suggests that intervention in a support-group format can be a successful alternative to an individual inpatient program for eating disorders in some young children.

The fidelity of DNA synthesis by the catalytic subunit of yeast DNA polymerase alpha alone and with accessory proteins

The fidelity of DNA synthesis catalyzed by the 180-kDa catalytic subunit (p180) of DNA polymerase alpha from Saccharomyces cerevisiae has been determined. Despite the presence of a 3'----5' exonuclease activity (Brooke et al., 1991, J. Biol. Chem., 266, 3005-3015), its accuracy is similar to several exonuclease-deficient DNA polymerases and much lower than other DNA polymerases that have associated exonucleolytic proofreading activity. Average error rates are 1/9900 and 1/12,000, respectively, for single base-substitution and minus-one nucleotide frameshift errors; the polymerase generates deletions as well. Similar error rates are observed with reactions containing the 180-kDa subunit plus an 86-kDa subunit (p86), or with these two polypeptides plus two additional subunits (p58 and p49) comprising the DNA primase activity required for DNA replication. Finally, addition of yeast replication factor-A (RF-A), a protein preparation that stimulates DNA synthesis and has single-stranded DNA-binding activity, yields a polymerization reaction with 7 polypeptides required for replication, yet fidelity remains low relative to error rates for semiconservative replication. The data suggest that neither exonucleolytic proofreading activity, the beta subunit, the DNA primase subunits nor RF-A contributes substantially to base substitution or frameshift error discrimination by the DNA polymerase alpha catalytic subunit.

Effect of obesity on plasma insulin-like growth factor-I in cancer patients

Starvation and malnutrition are associated with low concentrations of plasma insulin-like growth factor I (IGF-I). To evaluate the utility of IGF-I as a screening test for malnutrition, we compared plasma IGF-I concentrations with anthropometric measurements of nutritional status in 99 cancer patients. Forty-three percent of patients were overweight and 4 percent were underweight. Log IGF-I correlated negatively with body weight (r = -0.31, P = 0.002), midarm muscle area (MAMA) (r = -0.31, P = 0.001), triceps skinfold thickness (TSF) (r = -0.24, P = 0.03) and body mass index (r = -0.31, P = 0.003). In males plasma IGF-I correlated with TSF but not MAMA; in females IGF-I correlated with MAMA but not TSF, suggestive of a sexual dimorphism between plasma IGF-I and indices of adiposity. We conclude that obesity was far more prevalent than undernutrition, and that plasma IGF-I correlated negatively with indices of adiposity in a gender specific fashion. Because IGF-I is significantly reduced in the obese as well as in the malnourished, measurements of plasma IGF-I are unlikely to be of adequate clinical specificity to serve as a useful screening test for subtle alterations in nutritional status.

Shikimic acid complexes of platinum. Preparation, reactivity, and antitumor activity of (R,R-1,2-diaminocyclohexane) bis(shikimato) platinum(II). Evidence for a novel rearrangement involving platinum-carbon bond formation

The complex (R,R-1,2-diaminocyclohexane)bis(shikimato)platinum(II) (shikimato = the anion of 3R,4S,5R-trihydroxy-1-cyclohexene-1-carboxylic acid), I, has been synthesized and purified by high performance liquid chromatography (HPLC). The complex is only moderately stable in aqueous solution. Its major hydrolysis product, also purified by HPLC, is proposed to be a unique complex type in which a single shikimate group is coordinated through both the carboxylate oxygen and the C(2) vinylic carbon of the shikimate moiety [Pt(R,R-dach)(O,C-shikimato)], II. In vitro, complex I is active against L1210 leukemia and against an L1210 cell line with acquired resistance to cisplatin. In vivo, the complex is active against L1210, P388, and B16 melanoma; this activity is highly schedule-dependent. Complex II is also active against L1210 leukemia.

Exonucleolytic proofreading of leading and lagging strand DNA replication errors

We have asked whether exonucleolytic proofreading occurs during simian virus 40 origin-dependent, bidirectional DNA replication in extracts of human HeLa cells. In addition, we have compared the fidelity of leading and lagging strand DNA synthesis. In a fidelity assay that scores single-base substitution errors that revert a TGA codon in the lacZ alpha gene in an M13mp vector, providing an excess of a single dNTP substrate over the other three dNTP substrates in a replication reaction generates defined, strand-specific errors. Fidelity measurements with two vectors having the origin of replication on opposite sides of the opal codon demonstrate that error rates for two different A.dCTP and T.dGTP mispairs increase when deoxyguanosine monophosphate is added to replication reaction mixtures or when the concentration of deoxynucleoside triphosphates is increased. The data suggest that exonucleolytic proofreading occurs on both strands during bidirectional replication. Measurements using the two simian virus 40 origin-containing vectors suggest that base substitution error rates are similar for replication of the leading and lagging strands.

Heteroduplex repair in extracts of human HeLa cells

A general repair process for DNA heteroduplexes has been detected in HeLa cell extracts. Using a variety of M13mp2 DNA substrates containing single-base mismatches and extra nucleotides, extensive repair is observed after incubation with HeLa cell cytoplasmic extracts and subsequent transfection of bacterial cells with the treated DNA. Most, but not all, mispairs as well as two frameshift heteroduplexes are repaired efficiently. Parallel measurements of repair in HeLa extracts and in Escherichia coli suggest that repair specificities are similar for the two systems. The presence of a nick in the molecule is required for efficient repair in HeLa cell extracts, and the strand containing the nick is the predominantly repaired strand. Mismatch-dependent DNA synthesis is observed when radiolabeled restriction fragments, produced by reaction of the extract with heteroduplex and homoduplex molecules, are compared. Specific labeling of fragments, representing a region of approximately 1,000 base pairs and containing the nick and the mismatch, is detected for the heteroduplex substrate but not the homoduplex. The repair reaction is complete after 20 min and requires added Mg2+, ATP, and an ATP-regenerating system, but not dNTPs, which are present at sufficient levels in the extract. An inhibitor of DNA polymerase beta, dideoxythimidine 5'-triphosphate, does not inhibit mismatch-specific DNA synthesis. Aphidicolin, an inhibitor of DNA polymerases alpha, delta, and epsilom, inhibits both semiconservative replication and repair synthesis in the extract. Butylphenyl-dGTP also inhibits both replicative and repair synthesis but at a concentration known to inhibit DNA polymerase alpha preferentially rather than delta or epsilon. This suggests that DNA polymerase alpha may function in mismatch repair.

Formulation and evaluation of baits for oral rabies vaccination of raccoons (Procyon lotor)

Captive raccoons were offered a variety of vaccine containers and bait components in a series of three-choice tests. Paraffin wax ampules were the most readily accepted vaccine container. Preferred bait components included corn and shellfish oils, deep fried corn meal batter, and egg, apple and buttermilk flavorings. These results, together with factors including ease of bait formulation, cost, and suitability for field use, were used to develop an experimental delivery system for an oral rabies vaccine. The developed system was composed of a polyurethane sleeve (1.5 x 5.5 cm) dipped in a commercial food batter mix together with corn meal, milk and egg. The sleeve was deep fried in corn oil and a 2.0 ml ampule containing a recombinant rabies vaccine was then inserted into the sleeve bait. These baits were presented to 10 captive raccoons. Nine of the 10 animals developed high levels of rabies virus neutralizing antibodies. Field tests are needed to determine if the delivery system developed also is effective for wild raccoons.

Phase I trial of intraperitoneal recombinant interleukin-2/lymphokine-activated killer cells in patients with ovarian cancer

Ten patients with ovarian cancer refractory to conventional therapy were treated with intraperitoneal (i.p.) recombinant interleukin-2 (rIL-2) and lymphokine-activated killer cells (LAK). The 28-day protocol consisted of 6 priming i.p. rIL-2 infusions on days 0, 4, 6, 8, 10, and 12. Leukapheresis was performed for mononuclear cell collection on days 15, 16, 17, and 18 and lymphokine-activated killer cells were given i.p. with the rIL-2 on days 19 and 21. Three additional i.p. rIL-2 infusions were given on days 23, 25, and 27. Three dose levels of rIL-2 were tested: 5 X 10(5), 2 X 10(6), and 8 X 10(6) units/m2 body surface area. The dose-limiting toxicity was abdominal pain secondary to ascites accumulation with significant weight gain. Other toxic effects included decreased performance status, fever, nausea and vomiting, diarrhea, and anemia. Peripheral lymphocytosis and eosinophilia were seen at all dose levels. The maximum tolerated dose is 8 X 10(6) units/m2/dose. Peripheral and peritoneal IL-2 levels were measured with a bioassay using an IL-2-dependent cell line. At the highest dose level, serum IL-2 was greater than 10 units/ml for 18 h. After the first infusion, a 2-log dilution of the i.p. IL-2 was measured in the serum. In the postleukapheresis i.p. IL-2-dosing period less IL-2 was detected in the serum than in the earlier i.p. IL-2-priming period. The induction and persistence of LAK activity were studied. Peritoneal LAK activity was detected as early as 4 days after the first i.p. infusion, by day 11 in all evaluable patients, and persisted for the 6-day interval between priming IL-2 and LAK/IL-2 infusion. Peritoneal lytic activity persisted until day 28 in 5 tested patients. These peritoneal cells retained lytic activity 48 h in culture medium without rIL-2 present. Peritoneal LAK activity correlated with the percentage of mononuclear cells and the percentage of CD56-positive mononuclear cells in the peritoneum. The yield of peripheral lymphocytes after the six i.p. priming doses of rIL-2 correlated with the dose level of rIL-2 infused. Peripheral blood LAK activity showed a minimal, however progressive, increase during the treatment protocol. LAK activity could be enhanced if rIL-2 was present during the 4-h assay. These studies indicate that i.p. rIL-2 infusion induced durable regional LAK activity and primes peripheral blood cells for LAK activity if exposed briefly to additional IL-2.

Multicenter trial of single-dose modified bovine surfactant extract (Survanta) for prevention of respiratory distress syndrome. Ross Collaborative Surfactant Prevention Study Group

A multicenter, prospective randomized controlled trial was performed comparing the efficacy of a single intratracheal dose of modified bovine surfactant extract (Survanta, 100 mg/kg, Abbott Laboratory, North Chicago, IL) with air placebo in preventing respiratory distress syndrome. Infants were enrolled if they were estimated to be between 24 and 30 weeks' gestation, weighed between 750 and 1250 g, and were intubated and stabilized within 15 minutes after birth. A total of 160 infants were treated (79 with surfactant, 81 with air placebo) between 4 and 37 minutes after birth (median time 12 minutes). Of these, 5 infants were excluded from the final analysis. The 72-hour average values for the arterial-alveolar oxygen ratio, fraction of inspired oxygen, and mean airway pressure were calculated from the area under the curve of scheduled values measured throughout 72 hours. Clinical status was classified using five ordered categories (no supplemental oxygen or assisted ventilation, supplemental oxygen only, continuous positive airway pressure or assisted ventilation with intermittent mandatory ventilation less than or equal to 6 breaths/min, assisted ventilation with intermittent mandatory ventilation greater than 6 breaths/min, death). Chest radiographs at 24 hours were graded for severity of respiratory distress syndrome. Infants receiving Survanta had less severe radiographic changes at 24 hours of age and decreased average fraction of inspired oxygen (31% vs 42%, P = .002) compared with control infants. No differences were noted in the average arterial-alveolar oxygen ratio, mean airway pressure, or clinical status on days 7 and 28. A beneficial effect was noted in the incidence of pneumothorax (P = .057) and an increase was noted in the incidence of necrotizing enterocolitis (P = .052). No differences in incidence of patent ductus arteriosus, intraventricular hemorrhage, sepsis, or bronchopulmonary dysplasia were seen. According to results of a secondary analysis, there was improvement in the fraction of inspired oxygen and a greater number of survivors without bronchopulmonary dysplasia in the subgroup of infants weighing less than 1000 g who were treated with surfactant. It was concluded that a single dose of Survanta given shortly after birth resulted in decreased severity of chest radiographic findings 24 hours after treatment and improved oxygenation during 72 hours after treatment, but did not improve other acute measures of disease severity or clinical status later in the neonatal period. The group at highest risk for respiratory distress syndrome (infants with birth weights between 750 and 999 g) may benefit the most from preventive therapy.

Acute hematomas: effects of deoxygenation, hematocrit, and fibrin-clot formation and retraction on T2 shortening

Acute hematomas can appear hypointense on T2-weighted magnetic resonance (MR) images at field strengths as low as 0.35 T. Using Raman spectroscopy to measure blood oxygenation and taking T2 measurements at 2.1 and 9.4 T, the authors examined the relaxation mechanisms acting during deoxygenation, increases in hematocrit, and fibrin-clot formation and retraction. Individual contributions to overall T2 from deoxyhemoglobin and the interactions of water with protein hydration layers in hemoglobin, plasma proteins, and fibrin were measured. Overall T2 values estimated by summing individual relaxation rates were in reasonable agreement with the T2 values of clotted blood. Results suggest that deoxygenation may be most important in T2 shortening, followed by increased hematocrit. T2 shortening from fibrin polymerization was minimal at the field strengths used. Effects of deoxygenation and increasing hematocrit are more sensitive to field strength than fibrin T2 shortening. Effects of fibrin may be more significant at middle and low field strengths.

Efficiency factors and ATP/ADP ratios in nitrogen-fixing Bacillus polymyxa and Bacillus azotofixans

The efficiency factor, the number of moles of ATP generated per mole of glucose fermented, was determined in anaerobic, non-carbon-limited N2-fixing cultures of Bacillus polymyxa, Bacillus macerans, Bacillus azotofixans, and Clostridium butyricum through identification and quantitation of the fermentation products by 13C nuclear magnetic resonance spectroscopy and measurement of acetate kinase activities. All three Bacillus species had acetate kinase activities and produced acetate and ethanol as the major fermentation products. The maximum amounts of ATP generated per mole of glucose fermented were 2.70, 2.64, and 2.88 mol in B. polymyxa, B. macerans, and B. azotofixans, respectively, compared with 3.25 mol in C. butyricum. Thus, in the N2-fixing Bacillus species, the efficiency factors are lower than that in C. butyricum. Steady-state ATP/ADP concentration ratios were measured in non-carbon-limited N2-fixing cultures of B. polymyxa and B. azotofixans through separation and quantitation of the adenylates in cell extracts by ion-pair reversed-phase high-performance liquid chromatography. The observed ATP/ADP ratios were 4.5 and 3.8, and estimated energy charges were 0.81 to 0.86 and 0.81 to 0.83, respectively, for B. polymyxa and B. azotofixans. The results suggest that under these growth conditions, the rate of ATP regeneration is adequate to meet the energy requirement for N2 fixation in the Bacillus species, in contrast to N2-fixing Clostridium pasteurianum and Klebsiella pneumoniae, for which substantially lower steady-state ATP/ADP ratios and energy charges have been reported. Implications of the results are discussed in relation to possible differences between Bacillus and Clostridium species in energy requirements for N2 fixation and concomitant ammonia assimilation.

Six novel tachykinin- and bombesin-related peptides from the skin of the Australian frog Pseudophryne güntheri

Six novel peptides belonging to the tachykinin and bombesin families were isolated and sequenced from extracts of the skin of the Australian myobatrachid frog Pseudophryne güntheri. One of these peptides (PG-L) was of the bombesin family and may be considered an N-elongation of the litorin/ranatensin molecule, with which it shares an identical spectrum of activity on isolated smooth muscle preparations. The other five peptides were of the tachykinin family with two of these peptides (PG-SPI and PG-SPII) related to substance P and three (PG-KI, PG-KII and PG-KIII) to kassinin. In contrast to the basic nature of substance P, the PG-SP peptides showed a clear acidic character and displayed a more potent and sustained action on isolated smooth muscle preparations and rat blood pressure than did substance P. Two of the three PG-K peptides were more potent than kassinin; PG-KIII was considerably less potent. PG-KI and PG-KII were also present in a deamidated, poorly active, form.

Fidelity of animal cell DNA polymerases alpha and delta and of a human DNA replication complex

We are investigating the mechanisms by which mutations are produced or avoided during DNA synthesis. Using in vitro fidelity assays, we have defined the error frequency and mutational specificity of the replicative animal cell DNA polymerases (alpha and delta). With DNA polymerase alpha or the four-subunit DNA polymerase alpha-DNA primase complex, neither of which contains detectable associated exonuclease activity, the fidelity of the polymerization step is low relative to spontaneous mutation rates in vivo. DNA polymerase delta is much more accurate, partly due to proofreading by the 3'----5' exonuclease activity associated with this polymerase. These fidelity studies have been extended to the replication apparatus present in extracts of human HeLa cells. The replication complex is highly accurate, suggesting that additional fidelity components are operating in the extract during bidirectional, semiconservative replication of double-stranded DNA. Nevertheless, in highly sensitive reversion assays, base substitution errors can be readily detected at frequencies greater than the estimated rate of spontaneous mutation in vivo. This suggests that fidelity components may be missing and/or that human cells depend heavily on postreplicative repair processes to correct replication errors.