Development of a PCR-based allele-specific assay from an RFLP probe linked to resistance to cereal cyst nematode in wheat

The RFLP locus Xglk605 identified by the probe Tag605 maps to a proximal position on the long arm of wheat chromosome 2B about 7 cM away from a gene conditioning resistance to cereal cyst nematode in the wheat line AUS10894. The clone Tag605 was partially sequenced and the PCR primer set AWP1 was designed. The 292-bp product, which showed no polymorphism between varieties, was cloned and sequenced. A single base difference was found in the sequence of the AWP1 products amplified and cloned from the wheat lines AUS10894 and "Spear'. PCR primers were designed with 3' termini that corresponded to the two alleles. A dual-PCR system was developed in which the primer sets AWP2 and AWP3 produced allele-specific amplification. The concentration of the oligonucleotide primers and the sequence of the primer-template mismatches were critical to the success of discriminatory allele amplification.

Comparison of elderly and younger patients with out-of-hospital chest pain. Clinical characteristics, acute myocardial infarction, therapy, and outcomes

BACKGROUND

Acute myocardial infarction is associated with significantly higher mortality in elderly patients compared with younger patients.

OBJECTIVES

To determine clinical differences in elderly and younger patients with acute myocardial infarction. To assess differences in therapies and outcomes between the age groups.

METHODS

Over a 3.5-year period, 2482 consecutive adult emergency medical services patients with chest pain received prehospital electrocardiograms and were entered in the Milwaukee Prehospital Chest Pain Database in Milwaukee, Wis. Clinical characteristics that included cardiac history, description of chest pain, time of onset to presentation, and prevalence of acute myocardial infarction were obtained for all patients. Patients with acute infarction were further analyzed in reference to type of infarction (Q wave vs non-Q wave), therapeutic interventions, and mortality. Patients were stratified in 3 age groups: younger than 70 years (younger), 70 years or older (elderly), and 80 years or older (very elderly); differences were compared among the age groups.

RESULTS

Even though more than 50% had a history of documented coronary artery disease, elderly patients with ischemic chest pain delayed more than 6 hours in seeking medical assistance after onset of pain. In elderly patients whose chest pain represented an acute myocardial infarction, hospital mortality was double that of younger patients. Thrombolytic therapy reduced hospital mortality by approximately 50% in both younger and elderly patients, although thrombolytic therapies were used in only 17% of the elderly patients compared with 50% of the younger patients (P < .001). Revascularization procedures were also beneficial in elderly patients as well as in younger patients, although this procedure, as with thrombolytic therapy, was less frequently used in elderly patients (48% vs 32%, P < .001).

CONCLUSIONS

Effective methods for reducing time delays from onset of chest pain to accessing health care for elderly persons deserve investigation. Physicians should be aware of the benefits of thrombolytic and revascularization therapies in elderly patients with acute myocardial infarction.

A randomised comparison of meropenem with cefotaxime or ceftriaxone for the treatment of bacterial meningitis in adults. Meropenem Meningitis Study Group

Third-generation cephalosporins are presently the agents of choice for the empirical antimicrobial therapy of bacterial meningitis. However, a number of factors associated with these agents, namely the development of resistance by pneumococci, limited activity against some Enterobacteriaceae and Pseudomonas spp., and the possible adverse effects of their bacteriolytic mode of action, indicate that newer classes of antimicrobial agents be evaluated for the treatment of bacterial meningitis. Meropenem is a carbapenem antibiotic which is highly active against the major bacterial pathogens causing meningitis, and penetrates well into the cerebrospinal fluid. Two prospective randomised studies in 56 adult bacterial meningitis patients have compared meropenem 40 mg/kg 8-hourly, up to a maximum of 6 g/day (n = 28) with cephalosporin treatment, i.e. cefotaxime (n = 17) or ceftriaxone (n = 11). Patients were assessed by neurological examination, Glasgow Coma Score and Herson-Todd score. Clinical cure was observed in all 23 evaluable patients treated with meropenem (100%) and with 17 of the 22 evaluable cephalosporin-treated patients (77%). All pre-treatment isolates were eradicated except one isolate of Staphylococcus aureus in a cefotaxime-treated patient. Neurological sequelae were noted in three meropenem and four cephalosporin-treated patients. No patients in either treatment group experienced seizures after the start of therapy. This was despite the fact that a patient in each group had experienced seizures before therapy, several had underlying CNS disorders, and that doses of 6 g/day of meropenem were given. Hearing impairment was recorded in 11 meropenem and nine cephalosporin treated patients. Three patients in the meropenem group and one in the cephalosporin group died during treatment for reasons unrelated to study therapy. Overall, the results of this study indicate that meropenem is an effective and well-tolerated antibiotic for the treatment of bacterial meningitis in adults.

Mammalian assay for site-specific DNA damage processing using the human H-ras proto-oncogene

The human genomic H-ras proto-oncogene was inserted into an Epstein-Barr virus (EBV) vector (p220.2) that replicates synchronously with the cell cycle. Unique restriction enzyme sites, 30 bp apart, were created on either side of codon 12 to enable the construction of gapped heteroduplex (GHD) DNA. Depending upon experimental protocol, the gap could be located either on the coding (non-transcribed) strand or the non-coding (transcribed) strand. GHD DNA was created using a 1.8 kb segment of H-ras DNA containing exon 1, into which a synthetic 30 nucleotide oligomer containing a strand- and site-specific mismatched nucleotide was annealed. The 1.8 kb segment of H-ras DNA containing a codon 12; middle G:T, A:C or T:C mismatch has been religated with high efficiency into the EBV vector and transfected into NIH 3T3 cells using a mild liposome-mediated protocol. Subsequent hygromycin resistant NIH 3T3 colonies have been PCR amplified and sequenced. In this study, codon 12; middle nucleotide mismatch correction rates to wild-type G:C during replication in NIH 3T3 cells were 96.4% of G:T mismatches, 87.5% of A:C mismatches and 67% of T:C mismatches.

A reexamination of the NRMP matching algorithm. National Resident Matching Program

Most graduating medical students in the United States find their first professional appointments through the National Resident Matching Program (NRMP). This service receives rank-order lists of preferences from students and from hospitals, and then generates final assignments of students to hospitals through the use of a specific computerized matching algorithm. The author uses recent findings from the mathematics and economics literatures to demonstrate three difficulties with the NRMP's matching algorithm and the official descriptions thereof. First, the algorithm favors hospitals over students, a feature known to the NRMP since at least 1976, but, in the author's opinion, not made clear in NRMP literature for students. Second, the author argues that the NRMP's justification that its algorithm mimics orderly, noncentralized admission processes is not correct. Institutions operating under non-centralized procedures must typically make more initial offers than there are positions, in the realization that some fraction of their offers will be declined. This arrangement enlarges the choices available to many applicants, and thereby benefits them, whereas the NRMP's algorithm unrealistically assumes that no institution would ever send out any extra offers. Third, the NRMP's algorithm contains incentives for students to misrepresent their true preferences when constructing their rank-order lists. This feature is a substantial disadvantage of the current algorithm and is incorrectly described in literature distributed to students and in published articles from the NRMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of RFLP markers linked to the cereal cyst nematode resistance gene (Cre) in wheat

The cereal cyst nematode (CCN) (Heterodera avenae Woll.) is an economically damaging pest of wheat in many of the worlds cereal growing areas. The development of CCN-resistant cultivars may be accelerated by the use of molecular markers. The Cre gene of the wheat line "AUS 10894" confers resistance to CCN. Using a pair of near-isogenic lines (NILs) that should differ only in a small chromosome segment containing the Cre locus, we screened 58 group-2 probes and found two (Tag605 and CDO588) that detect polymorphism between the NILs. Nulli-tetrasomic and ditelosomic lines confirmed that the restriction fragment length polymorphism (RFLP) markers identified were derived from the long arm of wheat chromosome 2. Crosses between "AUS 10894" and "Spear" and the NIL "AP" and its recurrent parent "Prins" were used to produce F2 populations that gave the expected 3∶1 segregation ratio for the resistance gene. Linkage analysis identified two RFLP markers flanking the resistance gene. Xglk605 and Xcdo588 mapped 7.3 cM (LOD=6.0) and 8.4 cM (LOD=6.7), respectively, from the Cre locus.

Interaction of intravenous atrial natriuretic factor with furosemide in patients with heart failure

Furosemide is frequently administered intravenously to patients with chronic heart failure. However, use of diuretics may cause neuroendocrine activation and by itself may not consistently afford diuresis. Atrial natriuretic factor (ANF) in pharmacologic doses is a vasodilator and has favorable neuroendocrinologic effects in patients with congestive heart failure. To examine whether exogenous ANF might enhance the effects of acute furosemide injection, we studied 14 patients with chronic stable heart failure and measured the effects of the combination of ANF and furosemide on hemodynamics, neuroendocrine activation, and urine output. Eight patients were randomly assigned to receive placebo plus furosemide (1.3 mg/kg intravenously). Six patients received ANF (2 micrograms/kg intravenously) plus furosemide at the same dose in a double-blind manner. The group receiving placebo plus furosemide exhibited a slight increase in mean arterial pressure (92 to 96 mm Hg; p < 0.03), systemic vascular resistance (1989 to 2271 dynes.sec.cm-5; p = 0.0007), and pulmonary capillary wedge pressure (22 to 24 mm Hg; p < 0.04) from baseline to 10 minutes. The group receiving ANF plus furosemide exhibited no change in mean arterial pressure and systemic vascular resistance from baseline to 10 minutes. Pulmonary capillary wedge pressure and mean pulmonary pressure were unchanged. In the group receiving placebo plus furosemide.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipoprotein lipase and sphingomyelinase synergistically enhance the association of atherogenic lipoproteins with smooth muscle cells and extracellular matrix. A possible mechanism for low density lipoprotein and lipoprotein(a) retention and macrophage foam cell formation

Prominent features of atheromata include smooth muscle cells, cholesteryl ester-loaded macrophage foam cells, extracellular matrix, extracellularly trapped and aggregated lipoproteins, and various enzymes including lipoprotein lipase (LpL) and sphingomyelinase (SMase). The interplay of these factors was investigated in cell culture. Incubation of bovine aortic smooth muscle cells for 18 h at 37 degrees C with low density lipoprotein (LDL) in the presence of LpL and SMase led to massive aggregation of LDL on the surface of the cells as viewed by phase, fluorescence (using 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate-LDL), and electron microscopy. This aggregation required both enzymes. Studies with 125I-LDL confirmed these observations: 125I-LDL cell association in the presence of LpL plus SMase was 50-100-fold greater than in the absence of the two enzymes and was 10-fold greater than in the presence of either enzyme alone. A similar effect (68-fold enhancement) was seen with 125I-labeled lipoprotein(a) (Lp(a)), another atherogenic lipoprotein. In all cases, 125I-lipoprotein degradation was relatively low (< 5% of cell-associated material). LpL/SMase-mediated association of 125I-LDL with smooth muscle cells was still observed when enzymatically inactive LpL was used. The effect was markedly diminished when the smooth muscle cells were treated with a combination of chondroitin ABC lyase and heparitinase or when mutant Chinese hamster ovary cells that lack cell-surface proteoglycans were used, indicating a specific role for cellular proteoglycans. When smooth muscle cells with 125I-LDL or 125I-Lp(a) aggregates were rinsed and then coincubated with mouse peritoneal macrophages for a further 24 h, visible aggregates disappeared, and there was marked 125I-lipoprotein degradation. Electron micrographs after 24 h of co-culture showed lipid-laden, foamy macrophages situated on top of smooth muscle cells, suggesting that the macrophages phagocytosed and metabolized the smooth muscle cell-associated LDL aggregates. Last, 125I-LDL association with smooth muscle cell extracellular matrix was also synergistically enhanced by LpL and SMase, to a level that was 19-fold greater than in the absence of the two enzymes. Thus, the interaction of LDL and Lp(a) with four atheroma components, namely, smooth muscle cells, extracellular matrix, LpL, and SMase, represents a physiologically plausible mechanism for massive, focal retention and aggregation of atherogenic lipoproteins in the arterial wall with subsequent macrophage foam cell formation.

Codons 12 and 13 of H-ras protooncogene interrupt the progression of DNA synthesis catalyzed by DNA polymerase alpha

Mutagenesis of protooncogenes has been postulated to contribute to the initiation and progression of human cancer. Activating mutations in the H-ras gene are predominantly single-base substitutions and are most frequently identified at codons 12, 13, and 61. We have analyzed the effects of DNA sequence context at specific codons that are hot spots for ras mutation with respect to abnormalities in copying by purified DNA polymerase alpha, a major eucaryotic replication enzyme. Exon 1 of H-ras gene was inserted into M13 mp19, single-stranded DNA constructs were isolated, and the progression of synthesis by polymerase alpha was measured. Strong termination sites were found in codons 12 and 13. Pausing at these codons is abolished when the template is mutated at the middle base of codon 12, the same alteration that converts H-ras into an activated oncogene. Resistance of codon 12 in double-stranded constructs to digestion with restriction enzymes and computer investigation of the ras sequence suggest that these termination sites are in a region of secondary structure. The frequency of sequence alterations within DNA chains that have been extended past codons 12 and 13 was found to be < 0.01. We consider a variety of mechanisms by which the potential secondary structure involving codons 12 and 13 may contribute to the pausing of DNA polymerase alpha and to the generation of clustered mutations at this site.

Mechanisms by which lipoprotein lipase alters cellular metabolism of lipoprotein(a), low density lipoprotein, and nascent lipoproteins. Roles for low density lipoprotein receptors and heparan sulfate proteoglycans

We sought to investigate effects of lipoprotein lipase (LpL) on cellular catabolism of lipoproteins rich in apolipoprotein B-100. LpL increased cellular degradation of lipoprotein(a) (Lp(a)) and low density lipoprotein (LDL) by 277% +/- 3.8% and 32.5% +/- 4.1%, respectively, and cell association by 509% +/- 8.7% and 83.9% +/- 4.0%. The enhanced degradation was entirely lysosomal. Enhanced degradation of Lp(a) had at least two components, one LDL receptor-dependent and unaffected by heparitinase digestion of the cells, and the other LDL receptor-independent and heparitinase-sensitive. The effect of LpL on LDL degradation was entirely LDL receptor-independent, heparitinase-sensitive, and essentially absent from mutant Chinese hamster ovary cells that lack cell surface heparan sulfate proteoglycans. Enhanced cell association of Lp(a) and LDL was largely LDL receptor-independent and heparitinase-sensitive. The ability of LpL to reduce net secretion of apolipoprotein B-100 by HepG2 cells by enhancing cellular reuptake of nascent lipoproteins was also LDL receptor-independent and heparitinase-sensitive. None of these effects on Lp(a), LDL, or nascent lipoproteins required LpL enzymatic activity. We conclude that LpL promotes binding of apolipoprotein B-100-rich lipoproteins to cell surface heparan sulfate proteoglycans. LpL also enhanced the otherwise weak binding of Lp(a) to LDL receptors. The heparan sulfate proteoglycan pathway represents a novel catabolic mechanism that may allow substantial cellular and interstitial accumulation of cholesteryl ester-rich lipoproteins, independent of feedback inhibition by cellular sterol content.

Pancreatic pseudocyst: recommendations for operative and nonoperative management

From 1983 to 1990, 76 patients with pancreatic pseudocyst (PP) were managed. Computed tomographic scan (CT) was the primary diagnostic tool (88%). Ethanol accounted for 71 per cent and biliary disease 6 per cent of the occurrence of PP. Thirty-eight patients required surgery and 37 were managed nonoperatively. Forty-four PP complications occurred in 29 patients (4 bleeding, 1 ruptured, 13 gastric outlet obstruction, 10 infected, 6 hyperbilirubinemia, 5 pancreatic ascites, 5 pulmonary insufficiency) at a range of 1 day to 5 weeks from diagnosis; all but one occurred during initial hospitalization. Indications for surgery included complications,12 nonresolution or persistence of symptoms,18 and expansion.9 Internal drainage was accomplished in 40 per cent, (half within 4 weeks of diagnosis), 40 per cent underwent distal resection, and 15 per cent external drainage. There were two deaths in the series. Chronic pancreatitis, gallstone etiology, and gastric outlet obstruction significantly correlated with surgical management of the PP. Endoscopic retrograde cholangiopancreatography (ERCP) was helpful in planning the surgical procedure; 70 per cent of those undergoing ERCP had their operative plan altered. Percutaneous drainage failed in six of eight cases. The authors conclude that nonoperative management is safe and effective in 50 per cent of PP patients, if close radiographic follow-up is maintained until resolution.

Lipoprotein lipase modulates net secretory output of apolipoprotein B in vitro. A possible pathophysiologic explanation for familial combined hyperlipidemia

We showed previously that net secretory output of apolipoprotein B (apo B) from cultured human hepatoma cells (HepG2) is regulated by rapid reuptake of nascent lipoproteins before they have diffused away from the vicinity of the cells. We now sought to determine if the nascent lipoproteins could be remodeled to enhance or impede reuptake. We found that lipoprotein lipase (LpL), an enzyme that hydrolyzes lipoprotein triglyceride, reduced HepG2 output of apo B to one-quarter to one-half of control. The reduction was apparent during co-incubations as short as 2 h and as long as 24 h. Heparin, which blocks receptor-mediated binding of lipoproteins, abolished the effect of LpL on apo B output, without causing enzyme inhibition. To assess uptake directly, we prepared labeled nascent lipoproteins. LpL tripled the cellular uptake of labeled nascent lipoproteins, from 15.2% +/- 0.7% to 48.7% +/- 0.3% of the total applied to the cells. Cellular uptake of 125I-labeled anti-LDL receptor IgG was unaffected by LpL; thus, LpL enhanced reuptake by altering lipoproteins, not receptors. Because LpL is present in the space of Disse in the liver, we conclude that LpL may act on newly secreted lipoproteins to enhance reuptake in vivo. LpL deficiency would reduce local reuptake of apo B, which would appear as overproduction, thereby providing a mechanistic link between partial LpL deficiency and familial combined hyperlipidemia.

Multiple role juggling and daily mood states in working mothers: an experience sampling study

The effects of multiple role juggling (i.e., simultaneously attending to demands of different roles) on daily mood states of employed mothers were examined. Ss completed activity and mood questionnaires 8 times a day for 8 days. Multiple role juggling had immediate negative effects on task enjoyment and mood. However, contrast effects and habituation to role juggling occurred when mood and satisfaction were examined over time. Furthermore, mood states tended to spill over from one episode to the next within a day, but contrast effects were found across days. These results reflect the complex nature of psychological adjustment to multiple role occupancy.

Antibiotic treatment and associated prolonged prothrombin time

The incidence and type of pathology causing a prolonged prothrombin time and clinical bleeding episodes were assessed in a multicentre study of 1109 patients receiving cefotetan, a N-methyl-thiotetrazole (NMTT), or equivalent antibiotics. There was no significant difference in the incidence of a prolonged prothrombin time (9.9% with cefotetan, 8.0% with comparable antibiotics) of clinical bleeding episodes. However, prothrombin time increases of greater than 12 seconds were significantly (p = 0.002) greater with cefotetan (3.8%) than with comparators (0.8%). In both antibiotic groups increases in prothrombin time were more likely following surgery and in patients who were older, with a high platelet count, low albumin, or higher urea and creatinine concentrations. All antibiotic treatment can be associated with prolonged prothrombin times and new agents should always be assessed in a large multicentre study before the practical, clinical importance of haemostatic defects can be defined.

Synthesis of DNA by human immunodeficiency virus reverse transcriptase is preferentially blocked at template oligo(deoxyadenosine) tracts

The genome of human immunodeficiency virus (HIV) and especially the envelope gene are mutated with unusually high frequency during in vivo replication. Recent studies indicate that HIV reverse transcriptase (RT) is unusually error prone and that the number of generated mutations is disproportionately high within repetitive base sequences. To study the ability of recombinant and wild-type HIV RT to traverse specific homo-oligomeric stretches, we used bacteriophage M13 DNA templates that contain different oligo(purine) and oligo(pyrimidine) inserted tracts. The progress of HIV RT along these templates was potently inhibited from further progression only at a (dA)16 insert. Comparison with other polymerases indicates that the almost complete blockage of polymerization beyond an oligo(dA) insert is unique to HIV RT and Moloney murine leukemia virus RT, which has high sequence homology with HIV RT. The extent of termination of HIV RT at the oligo(dA) run is not affected by alterations in the concentration of KCl, Mg2+, dNTP, or by a decrease in pH. Obstruction of HIV RT opposite the oligo(dA) insert is not alleviated by moving the primer position further upstream from the oligo(dA) insert. Lastly, HIV RT purified directly from virions is also specifically arrested at an oligo(dA) tract. Competition experiments indicate that the concentration of active HIV RT in the presence of M13(dA)16 DNA is similar to that observed in the presence of M13(dG)16 DNA. In addition, preincubation of M13(dA)16 DNA with HIV RT does not subsequently inhibit avian myeloblastosis virus RT from successfully traversing the (dA)16 insert. Therefore, it appears that the blockage of chain elongation of HIV RT at the (dA)16 insert is not the result of trapping the enzyme at this site.

The unstirred water layer as a site of control of apolipoprotein B secretion

Apolipoprotein B-100 (apoB) is a constituent of low density lipoproteins that has been implicated in the development of coronary artery disease (Editorial (1988) Lancet 1, 1141-1142). It is produced primarily in the liver, but mechanisms of secretory control are unclear. We examined the possibility that rapid reuptake of newly secreted lipoproteins regulates the net output of apoB by cultured liver cells. Polyclonal blocking antibodies to the low density lipoprotein receptor markedly increased apoB output, and varying the width of the unstirred water layer around the cells also changed apoB output, consistent with local reuptake. Labeled apoB added to the bulk fluid phase of the incubation media was not detectably taken up, implying that re-uptake is predominantly local. We conclude that a major site of apoB secretory control resides in the unstirred water layer, external to the cell. Because many cells secrete products for which they possess receptors, local re-uptake from the unstirred water layer may be a general mechanism for secretory control.

The effect of a self-care minimal intervention for colds and flu on the use of medical services

OBJECTIVE

To determine the impact of mailed distribution of a brief self-care pamphlet on upper respiratory infection (URI)-related-medical care utilization.

DESIGN

Randomized controlled clinical trial with randomization by physician panel.

SETTING

Health maintenance organization.

PATIENTS

20,127 patients assigned to the panels of 22 primary care physicians randomly divided into an experimental group (n = 12,353) and a control group (n = 7,774), each consisting of 11 physician panels.

INTERVENTION

A mailed four-page self-care pamphlet for URI care.

MEASUREMENTS AND MAIN RESULTS

The medical records and survey data of a random sample of 790 persons were studied during a baseline period and an intervention period. URI visit rates decreased 14% more in the experimental group versus the control group (p = 0.878). Appropriateness of URI visits during the intervention period in the experimental group (80%) was comparable to that in the control group (76%). URI drug prescriptions during the intervention period for all 20,127 patients showed no significant difference.

CONCLUSIONS

A simple mailed self-care pamphlet has little effect on medical care utilization for URI care.

Ecosystem-level patterns of primary productivity and herbivory in terrestrial habitats

Ecosystems are structurally organized as food webs within which energy is transmitted between trophic levels and dissipated into the environment. Energy flow between two trophic levels is given by the amount of production at the lower level and by the proportion of production that is consumed, assimilated and respired at the higher level. Considerable evidence indicates that food-web structure varies predictably in different habitats, but much less is known about quantitative relationships among food web fluxes. Many of the energetic properties of herbivores in African game parks are associated with rainfall and, by inference, with net primary productivity. Respiratory costs per unit production at the consumer trophic level are higher for homeotherms than for heterotherms. Plant secondary chemicals affect herbivore dietary choices and the allocation of plant resources to those chemicals varies with resource availability. How these phenomena are translated into ecosystem fluxes is unknown. We present evidence that herbivore biomass, consumption and productivity are closely correlated with plant productivity, suggesting that the latter is a principal integrator and indicator of functional processes in food webs.

Ecosystem-level patterns of primary productivity and herbivory in terrestrial habitats

Ecosystems are structurally organized as food webs within which energy is transmitted between trophic levels and dissipated into the environment. Energy flow between two trophic levels is given by the amount of production at the lower level and by the proportion of production that is consumed, assimilated and respired at the higher level. Considerable evidence indicates that food-web structure varies predictably in different habitats, but much less is known about quantitative relationships among food web fluxes. Many of the energetic properties of herbivores in African game parks are associated with rainfall and, by inference, with net primary productivity. Respiratory costs per unit production at the consumer trophic level are higher for homeotherms than for heterotherms. Plant secondary chemicals affect herbivore dietary choices and the allocation of plant resources to those chemicals varies with resource availability. How these phenomena are translated into ecosystem fluxes is unknown. We present evidence that herbivore biomass, consumption and productivity are closely correlated with plant productivity, suggesting that the latter is a principal integrator and indicator of functional processes in food webs.

Correlation between the induction of heat shock protein 70 and enhanced viral reactivation in mammalian cells treated with ultraviolet light and heat shock

Enhanced viral reactivation (EVR) is considered to be one manifestation of an inducible response to DNA damage in mammalian cells analogous to the SOS response in Escherichia coli. EVR is characterized by the increased survival of ultraviolet (UV)-irradiated virus in cells which have been pretreated with DNA-damaging agents or by another type of cellular stress, heat shock (HS). In this study, we have analyzed the induction of nuclear proteins from Vero cells treated with either UV or HS, with the goal of identifying the protein(s) which mediate the EVR response. Results of 2-dimensional protein gel electrophoresis and fluorographic analysis of [35S]methionine-labeled nuclear proteins showed that UV-irradiation caused the increased synthesis of five proteins at 4-9 h after treatment. At 19-24 h, one of these proteins was still being synthesized at a higher level in UV-irradiated cells, and there were nine additional proteins whose syntheses were enhanced over control levels. In contrast, HS induced only one Mr 72,000 nuclear protein whose synthesis was maximal during the 4-9-h labeling period and corresponded to one of the proteins induced by UV at 19-24 h. Subsequent Western and Northern blot analyses have confirmed that this protein is a member of the heat shock protein (hsp) 70 family. Elevated nuclear levels of this protein correlated temporally with the maximum EVR response induced by each treatment (4 h after HS and 24 h after UV). Since the kinetics of EVR is different following UV and HS and parallels the difference in the induction of nuclear levels of hsp70 following each treatment, the results suggest that hsp70 may be involved in mediating the EVR response. In addition, this protein may also play a role in the recovery of DNA synthesis in UV-irradiated cells.

Effects of apolipoproteins A-IV and A-I on the uptake of phospholipid liposomes by hepatocytes

We examined the effects of apolipoproteins A-IV and A-I on the catabolism of whole particles by hepatoma G2 cells and cultured primary hepatocytes. For this type of experiment, high density lipoprotein is unsuitable, because all of its lipid and protein components independently dissociate and exchange and hence poorly trace whole particle catabolism. We therefore used phosphatidylcholine liposomes with radioactive tracers entrapped within their aqueous cores. Apolipoproteins A-IV, A-I, or E added to liposomes became liposome-associated and produced no detectable release of encapsulated label. As a positive control, apolipoprotein E doubled the uptake of labeled liposomes by hepatoma cells, compared to apolipoprotein-free controls, and this increase could be blocked by the addition of excess unlabeled low density lipoprotein. Degradation of labeled liposomes by hepatoma cells was increased 6-fold by the addition of apolipoprotein E. In contrast, neither apolipoprotein A-IV nor A-I increased cellular uptake or degradation of the particles. Similar results were obtained with primary hepatocytes. In studies using apolipoprotein combinations, apolipoproteins A-IV and A-I were each able to displace apolipoprotein E from liposomes and thereby reduce cellular uptake. Our data indicate that apolipoproteins A-IV and A-I do not facilitate uptake or degradation of whole particles by liver-derived cells in vitro. However, these apolipoproteins may modulate receptor-mediated uptake of particles by reducing the amount of particle-bound apolipoprotein E.

Intralipid infusion abolishes ability of human serum to cholesterol-load cultured macrophages

Intralipid is widely used for intravenous alimentation and contains triglyceride-emulsion particles and phospholipid liposomes. After infusion, triglyceride-emulsion particles resemble chylomicron remnants and thus may be atherogenic. On the other hand, intravenous infusion of phospholipid liposomes produces regression of experimental atherosclerosis and abolishes the ability of hypercholesterolemic rabbit plasma to cholesterol-load cultured macrophage foam cells. To determine the net effect of intralipid infusion on cellular cholesterol balance, J-774 macrophages were incubated for 18 hours with human serum obtained before, during, and after a 6-hour infusion of 10% Intralipid. Compared to serum-free medium, pre-infusion serum increased cellular unesterified cholesterol by 76% and cholesteryl ester by 78%. In contrast, serum obtained after the 6-hour infusion reduced cellular unesterified cholesterol by 23% and cholesteryl ester by 15%. Serum obtained 18 hours after the end of the infusion still showed impaired cholesterol-loading ability. Mouse peritoneal macrophages incubated with these serum samples behaved similarly. Compared to pre-infusion serum, postinfusion serum inhibited cellular uptake of 125I-low density lipoprotein and 125I-very low density lipoprotein by 50% and 80%, respectively, and also enhanced the efflux of cellular cholesterol by 46%. We conclude that the ability of human serum to cause cholesterol accumulation in cultured macrophages is abolished by an infusion of Intralipid. This effect is mediated by a reduction in cholesterol uptake by the cells and by an increase in cell cholesterol efflux. If similar events occur in the arterial wall, Intralipid infusion might inhibit foam cell formation in vivo.

Macrophage cholesterol removal by triglyceride-phospholipid emulsions

Phospholipid liposomes were previously shown to mobilize cholesterol from cultured macrophage foam cells. Because Intralipid, a clinically available triglyceride-phospholipid emulsion, contains both phospholipid liposomes and triglyceride-emulsion particles, we sought to study its effect on macrophage cholesterol mobilization. Following an 18h incubation of J774 macrophages in serum-free medium supplemented with Intralipid, cholesteryl ester content decreased by up to 50% in previously cholesterol-loaded cells, and by 25% in non-loaded cells. Both components of Intralipid, liposomes and emulsion particles, independently caused reductions in cellular cholesteryl ester. We conclude that clinically available triglyceride-phospholipid emulsions can mobilize macrophage cholesterol in vitro.

Single-dose prophylaxis with cefotetan in elective abdominal surgery. A controlled trial

Single dose cefotetan was compared with either a combination of metronidazole and cefazolin given for 24 hours or 3 doses of cefuroxime as prophylaxis in elective abdominal surgery. Wound infections and infections at remote sites (UTI and RTI) were similar in all groups. In a third group prophylaxis of abdominal surgery using a single 2g dose of cefotetan was compared to 2 doses of the same drug, given 12 hours apart. There was no demonstrable advantage to giving 2 doses. The low incidence of post-operative infections seen in all groups indicates the efficacy of cefotetan in the surgical prophylaxis of elective abdominal surgery.

Ceftazidime sodium carbonate versus ceftazidime arginine as empirical monotherapy in febrile neutropenic patients

A prospective randomized trial was conducted to determine the efficacy and safety of ceftazidime sodium carbonate versus a new arginine formulation of ceftazidime as empirical monotherapy in 100 febrile neutropenic patients. The clinical cure rate for ceftazidime sodium carbonate was 91% and for ceftazidime arginine 83%. Forty-two infections could be confirmed bacteriologically. Bacteriological cure rates were 87% and 81% respectively. Only one fatal infection-related outcome occurred during the first three days of therapy (ceftazidime arginine, Corynebacterium parvum). No failures were recorded in bacteriologically proven gram-negative infections. Ceftazidime was confirmed to be safe and effective as empirical monotherapy in febrile neutropenic patients. The arginine formulation is as effective and safe as the sodium carbonate formulation, but easier to handle.

Low density lipoprotein receptor-independent hepatic uptake of a synthetic, cholesterol-scavenging lipoprotein: implications for the treatment of receptor-deficient atherosclerosis

The metabolism of infused 111In-labeled phospholipid liposomes was examined in Watanabe heritable hyperlipidemic (WHHL) rabbits, which lack low density lipoprotein (LDL) receptors, and in normal control rabbits. The half-times (t1/2) for clearance of 111In and excess phospholipid from plasma were 20.8 +/- 0.9 hr and 20.3 +/- 4.6 hr in WHHL and 20.0 +/- 0.8 hr and 19.6 +/- 2.2 hr in the normal rabbits (means +/- SEM; n = 4). By 6 hr postinfusion, the plasma concentration of unesterified cholesterol increased by 2.2 +/- 0.23 mmol/liter in WHHL and 2.1 +/- 0.04 mmol/liter in normal rabbits, presumably reflecting mobilization of tissue stores. Disappearance of excess plasma cholesterol was greater than 90% complete in both groups of rabbits by 70 hr postinfusion. By quantitative gamma camera imaging, hepatic trapping of 111In-labeled liposomes over time was indistinguishable between the two groups. At autopsy, the liver was the major organ of clearance, acquiring 22.0% +/- 1.7% (WHHL) and 16.8% +/- 1.0% (normal of total 111In. Aortic uptake of 111In was less than 0.02%. Thus, mobilization of cholesterol and hepatic uptake of phospholipid liposomes do not require LDL receptors. Because phospholipid infusions produce rapid substantial regression of atherosclerosis in genetically normal animals, our results suggest that phospholipid liposomes or triglyceride phospholipid emulsions (e.g., Intralipid) might reduce atherosclerosis in WHHL rabbits and in humans with familial hypercholesterolemia.

Effect of lecithin:cholesterol acyltransferase on distribution of apolipoprotein A-IV among lipoproteins of human plasma

The effect of cholesterol esterification on the distribution of apoA-IV in human plasma was investigated. Human plasma was incubated in the presence or absence of the lecithin:cholesterol acyltransferase (LCAT) inhibitor 5,5-dithiobis(2-nitrobenzoic acid) (DTNB) and immediately fractionated by 6% agarose column chromatography. Fractions were monitored for apoA-IV, apoE, and apoA-I by radioimmunoassay (RIA). Incubation resulted in an elevated plasma concentration of cholesteryl ester and in an altered distribution of apoA-IV. After incubation apoA-IV eluted in the ordinarily apoA-IV-poor fractions of plasma that contain small VLDL particles, LDL, and HDL2. Inclusion of DTNB during the incubation resulted in some enlargement of HDL; however, both cholesterol esterification and lipoprotein binding of apoA-IV were inhibited. Addition of DTNB to plasma after incubation and prior to gel filtration had no effect on the apoA-IV distribution when the lipoproteins were immediately fractionated. Fasting plasma apoE was distributed in two or three peaks; in some plasmas there was a small peak that eluted with the column void volume, and, in all plasmas, there were larger peaks that eluted with the VLDL-LDL region and HDL2. Incubation resulted in displacement of HDL apoE to larger lipoproteins and this effect was observed in the presence or absence of DTNB. ApoA-I was distributed in a single broad peak that eluted in the region of HDL and the gel-filtered distribution was unaffected by incubation either in the presence or absence of DTNB. Incubation of plasma that was previously heated to 56 degrees C to inactivate LCAT resulted in no additional movement of apoA-IV onto lipoproteins, unless purified LCAT was present during incubation. The addition of heat-inactivated LCAT to the incubation, had no effect on movement of apoA-IV. These data suggest that human apoA-IV redistribution from the lipoprotein-free fraction to lipoprotein particles appears to be dependent on LCAT action. The mechanism responsible for the increased binding of apoA-IV to the surface of lipoproteins when LCAT acts may involve the generation of "gaps" in the lipoprotein surface due to the consumption of substrate from the surface and additional enlargement of the core. ApoA-IV may bind to these "gaps," where the packing density of the phospholipid head groups is reduced.

Phospholipid liposomes acquire apolipoprotein E in atherogenic plasma and block cholesterol loading of cultured macrophages

A single infusion of phospholipid liposomes promptly and persistently abolished the ability of hypercholesterolemic rabbit plasma to cause cholesteryl ester loading in cultured macrophages. This phospholipid enrichment of plasma caused moderate stimulation of cellular cholesterol efflux and, unexpectedly, almost complete inhibition of cellular uptake of beta-very low density lipoprotein (beta-VLDL), the major cholesteryl ester-rich particle in hypercholesterolemic rabbit plasma. Cell viability and LDL receptor activity were unaffected. Incubation of liposomes with beta-VLDL resulted in transfer of apolipoprotein-E (apoE) to the liposomes; reisolated apoE-phospholipid liposomes then competed efficiently for cellular apoprotein receptors. Thus, a major mechanism by which phospholipid infusions result in diminished accumulation of cholesteryl ester in cultured macrophages is by blocking cellular uptake of beta-VLDL. The liposomes deplete beta-VLDL of apoE, then compete for receptor-mediated uptake. These results suggest a novel mechanism contributing to the known antiatherogenic effect of phospholipid infusions: infused liposomes acquire apoE, then block uptake of atherogenic lipoproteins by arterial wall macrophages.

Ceftazidime does not enhance cyclosporin-A nephrotoxicity in febrile bone marrow transplantation patients

Ceftazidime was used as monotherapy for 30 febrile episodes in 28 patients, who underwent allogeneic bone marrow transplantation and who were treated concomitantly with the immunosuppressive agent cyclosporin-A. Ceftazidime did not enhance the well established nephrotoxicity of cyclosporin-A as measured by serum creatinine levels or creatinine clearance. Although an increasing number of Gram-positive infections in these patients warrants vigilance, ceftazidime as initial empirical monotherapy proved to be successful in 95% of all febrile post-transplantation patients. All Gram-negative and 69% of the Gram-positive infections were cured with ceftazidime alone. The overall clinical cure rate was 72%, with microbiological clearance in 63%. This compares favourably with aminoglycoside containing schedules and avoids the aminoglycoside associated nephrotoxicity.

Ceftazidime alone for treating Pseudomonas aeruginosa septicaemia in neutropenic patients

Twenty-nine patients with primary or secondary hypoplastic bone-marrow were treated successfully with ceftazidime alone for established septicaemia caused by Pseudomonas aeruginosa of which 38% strains were gentamicin-resistant . All the patients were neutropenic at the start of therapy; most were cured with microbiological confirmation before the bone marrow had regenerated. One patient died of cerebral haemorrhage due to profound thrombocytopenia without evidence of infection at autopsy. Significant toxicity was not observed. Ceftazidime alone is, therefore, a safe and effective treatment for infections caused by this organism even in the neutropenic patient.

Recognition of vesicular lipoproteins by the apolipoprotein B,E receptor of cultured fibroblasts

Vesicular lipoproteins (e.g., lipoprotein-X) are found in plasma in cholestasis or following infusion of Intralipid or phospholipid. To investigate the metabolism of vesicular lipoproteins, we isolated them from the plasma of subjects with cholestasis or following chronic or single Intralipid infusion. Cholestasis and chronic Intralipid therapy were found to be associated with elevated plasma concentrations of apoE, as determined by radioimmunoassay. Vesicular lipoproteins purified from each of the three types of plasma contained apoE, as well as other proteins. In cholestasis, in which levels of apoE were up to five times normal, a major portion of the plasma apoE was on vesicular lipoproteins. Normalized for apoE content, all preparations of vesicular lipoproteins displaced 125I-labeled LDL from apoB,E receptors of cultured fibroblasts identically. This displacement was inhibited by monoclonal antibodies that block receptor binding of apoE. Vesicular lipoproteins containing 125I-labeled apoE were internalized and degraded by fibroblasts. Different preparations caused small losses or gains of cellular cholesterol, with appropriate stimulation or suppression of apoB,E receptors. Thus, vesicular lipoproteins contain apoE, and apoE mediates their interaction with the apoB,E receptor. Our results suggest that the catabolism of cholesterol-rich vesicular lipoproteins, formed during cholestasis or following infusions of Intralipid or phospholipid, may be receptor-mediated.

Uptake of endogenous cholesterol by a synthetic lipoprotein

The addition of cholesterol-poor phospholipid liposomes to canine plasma in vivo and in vitro substantially alters the distribution of phospholipids, apoproteins, and, especially, cholesterol. In vivo, intravenously injected phospholipid liposomes remain discrete particles, which are readily distinguished from the normally occurring lipoproteins by their buoyant density and electrophoretic mobility. They acquire unesterified cholesterol from endogenous sources, thereby producing an acute rise in the concentration of this sterol in plasma. The liposomes also accumulate endogenous proteins, one of which is identified as apolipoprotein A-I. In vitro, phospholipid liposomes incubated with plasma acquire unesterified cholesterol and apolipoprotein A-I at the expense of high-density lipoproteins (HDL), the major carrier of cholesterol in normal canine plasma. In exchange, the HDL particles are enriched in phospholipids and become larger. At sufficiently high concentrations, the liposomes nearly completely deplete HDL of its unesterified cholesterol. Thus, there are generated two types of particles, both rich in apolipoprotein A-I and phospholipid, but one (modified HDL) containing mainly esterified cholesterol in its core and the other (modified liposomes) containing mainly unesterified cholesterol at its surface. It is concluded that phospholipid liposomes produce important changes in the distribution of lipids and protein in canine plasma, particularly at the expense of HDL. These changes appear to favor the mobilization of tissue cholesterol into the plasma, and may have application to atherosclerosis.

Teratogenic dose-response relationships of etretinate in the golden hamster

Etretinate (Ro 10-9359; Tigason; 4-methoxy-2,3,6-trimethylphenyl analog of retinoic acid, ethyl ester) was evaluated for teratogenic activity in the Syrian golden hamster. Groups of pregnant hamsters were given a single oral dose of 2.8-88 mg/kg etretinate during the early primitive streak stage of gestation. No signs of maternal intoxication were observed in any of the hamsters given the retinoid and maternal body weight changes throughout gestation were not significantly different from those of the vehicle-treated group. Etretinate administration was associated with a dose-dependent increase in the incidence and severity of malformations. The average fetal body weight was significantly less in litters recovered from dams given 44 or 88 mg/kg of etretinate when compared to the average body weight of fetuses recovered from dams given an equivalent volume of the vehicle. The average crown-rump lengths also were significantly shorter in fetuses taken from the dams given 44 or 88 mg/kg etretinate as compared to the control group. The malformations induced by etretinate administration were similar to those noted following an oral dose of all-trans-retinoic acid (Willhite and Shealy, 1984). A comparison of the dose-response curves for induction of terata following treatment with etretinate or all-trans-retinoic acid revealed that etretinate was twice as potent as a teratogen in the hamster as all-trans-retinoic acid. Teratogenic activity of etretinate in the hamster was achieved at doses (mg/kg body wt) used in patients at current clinical therapeutic levels.

The failure of serum albumin to affect capillary permeability in the isolated rabbit heart

The method of local tissue clearance was used to measure capillary permeability-surface area products (PS) for [3H]inulin and [14C]sucrose in the left ventricular wall of the isolated rabbit heart. As soon as a heart was excised, its coronary arteries were perfused with Ringer solution at 37 degrees for at least 30 min before clearance trials were begun. In paired trials, Ringer perfusion fluid containing 1% bovine serum albumin (Sigma) was compared with protein-free Ringer solution in terms of sucrose PS (PSs), inulin PS (PSi), and the PS ratio (Pi/Ps). With or without protein, the mean Pi/Ps was significantly less than the ratio of the free diffusion coefficients. With the untreated albumin, flow resistance rose markedly, and the PSs of both solutes fell but not Pi/Ps. To remove the unidentified vasoactive contaminant (which apparently resisted dialysis), the albumin was "defatted" by the procedure of R. F. Chen (1967, J. Biol. Chem. 242, 173-181). Defatted albumin (1% in the perfusion fluid) did not affect the volume of distribution (lambda) of sucrose or inulin in the myocardium, the heart rate, coronary flow, flow resistance, PSs, PSi, or Pi/Ps. Apparently bovine serum albumin does not influence capillary permeability in the rabbit heart. A protein effect on permeability, however, could have been missed if it has a long latent period (more than 15 min) or a long persistence (more than 30 min).

A direct bone marrow chromosome technique for acute lymphoblastic leukemia

We describe a direct bone marrow chromosome technique that was developed especially for use in studies of acute lymphoblastic leukemia (ALL). The features responsible for technical improvements include: the use of RPMI 1640 medium, supplemented with 30% fetal calf serum, to support cellular activity during both specimen transport and Colcemid treatment; the processing of only 0.1 ml of sedimented cells or less per centrifuge tube; the exposure of cells to Colcemid for a maximum of 25 min; control of the total time of exposure to hypotonic solution; the use of a steel wire as a stirring rod (fashioned to fit the centrifuge tube) for mixing cells; slide preparation by a specific edging-flaming technique; the natural aging of the slides to achieve optimal drying; and the use of a modified G-banding procedure that employs Wright's stain. This technique has been used in more than 350 cases of ALL and has consistently provided analyzable banded chromosomes, even in hyperdiploid cases with up to 91 chromosomes. It makes the previously recognized morphological difference between metaphases of residual normal cells and those from the leukemic clone less apparent. The edging-flaming technique of slide preparation is the most important component and is especially appropriate for spreading large numbers of chromosomes in ALL.

Structure-activity relationships of retinoids in developmental toxicology. I. Studies on the nature of the polar terminus of the vitamin A molecule

The teratogenic activities of all-trans-retinoyl fluoride, all-trans-3-retinylidene-2,4-pentanedione, all-trans-2-retinylidene-1,3-cyclopentanedione, all-trans-2-retinylidene-5,5-dimethyl-1,3-cyclohexanedione, all-trans-2-retinylidene-5-p-methoxyphenyl-1,3-cyclohexanedione, all-trans-2-retinylidene-1,3-cyclooctanedione, all-trans-5-[2,6-dimethyl-8-(2,6,6-trimethylcyclohexen-1-yl)-1,3, 5,7-octatetrae n-1-yl]tetrazole, ethyl all-trans-9-(exo-2-bicyclo[2.2.1.]heptyl)-3,7-dimethyl-2,4,6,8- nonatetraenoate, ethyl all-trans-4-[2-methyl-4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-1,3- butadien-1-yl]benzoate, 13-cis-N-(4-hydroxyphenyl)retinamide, and 13-cis-N-(2-hydroxyethyl)retinamide were determined in the hamster and compared with that of all-trans-retinoic acid. Administration of a single oral dose of the retinoids failed to induce signs of the hypervitaminosis A intoxication syndrome in any of the dams, and the maternal weight gain was not significantly different from the vehicle control value, except following intubation of the retinamides where maternal weight gain was significantly depressed. All of the retinylidene 1,3-diketones studied here were devoid of significant teratogenic activity. The retinamides failed to induce either an elevated mean litter frequency of malformed fetuses or a syndrome of anomalies similar to that induced by administration of an equimolar dose of all-trans-retinoic acid. All of the other retinoids induced a syndrome of malformations similar to that induced by administration of all-trans-retinoic acid and were associated with a significant increase in the number of litters containing one or more malformed fetuses and an elevated mean litter frequency of malformed fetuses. The teratogenic activity in the hamster of this series of retinoids was independent of structural modifications in either the beta-cyclogeranylidene ring or the polyene chain of the molecule. The results of the present study suggest that the changes in teratogenic activity associated with structural modification of vitamin A at C15 were primarily dependent upon the presence of or biotransformation to a free carboxyl or a moiety with an equivalent pKa at C15, not upon the molecular size of the substituent or the stereochemical position about C13. Since major structural modifications of vitamin A were made without the substantial loss of teratogenic activity, the structural requirements of retinoids for induction of terata were not extraordinarily exacting.