Defining the minimal portion of the retinoblastoma protein that serves as an efficient substrate for cdk4 kinase/cyclin D1 complex

We have determined the minimal portion of the retinoblastoma protein (Rb) that can serve as an efficient substrate for in vitro phosphorylation by cdk4 kinase-D1 cyclin. Kinetic measurements indicate that in vitro, a 15-kDa fragment that represents the C-terminus of Rb can serve equally well as a substrate when compared with the larger 56-kDa fragment of Rb, which contains the A, B and C domains. By comparison, peptide substrates appear to be 1000-fold less efficient. Furthermore, mutational analysis indicates that not all of the five phosphorylation sites within this minimal C domain are phosphorylated equally by cdk4/D1. Ser795 is the preferred phosphorylation site, whereas the four remaining sites Ser807, Ser811, Thr821 and Thr826 are phosphorylated to a much lesser degree. Truncations of the C domain from the carboxy terminus indicate that almost all of this domain is required for efficient phosphorylation. These data suggest that the structural context of the phosphorylation site within the substrate is critical for its phosphorylation by the cdk4/D1 kinase.

Permeability of the blood-brain barrier to neurotrophins

To evaluate the feasibility of applying blood-borne neurotrophins to promote normal function of the central nervous system (CNS) and to rescue neuronal degeneration, we characterized the permeability of the blood-brain barrier (BBB) to neurotrophins. We report here that some members of the neurotrophin family (NGF, betaNGF, NT3, and NT5) can cross the BBB of mice in vivo to arrive at the brain parenchyma. BBB permeability differed among individual neurotrophins in that NGF had the fastest influx rate (Ki) and NT3 the slowest, and that the entry rate of NGF was twice that of its smaller bioactive subunit betaNGF. BBB permeability also differed at various CNS regions in that the cervical spinal cord had the greatest rate of influx, whereas brain had the lowest. Saturability of influx was suggested by self-inhibition studies for NT3 in vivo, and for NGF in an in situ brain perfusion system, indicating the presence of saturable transport systems. The results suggest that peripheral administration of neurotrophins could have therapeutic effects within the CNS.

Comparative effects of losartan and captopril on ventricular remodeling and function after myocardial infarction in the rat

OBJECTIVE

To determine the effects of losartan and captopril treatment on ventricular remodeling and function after myocardial infarction in rats.

METHODS

Thirty-two rats with MI induced by coronary ligation after seven days were divided into four groups randomly and treated with captopril(2 g.liter-1, group A), losartan(10 mg.kg-1.d-1, group B), losartan(30 mg.kg-1.d-1, group C) and placebo (no drug, group D) for six weeks, respectively. Sham-operated rats(group E) served as controls. Echocardiography was performed at 1 and 7 weeks after MI, respectively.

RESULTS

Compared with the results before treatment, both LV end-diastolic internal diameter and volume decreased significantly and the thickened posterior wall was reversed in group A, B and C; the peak early filling velocity decreased whereas the peak velocity was increased in these three groups. There are no significant difference among the three treated groups. However, LV end-diastolic internal diameter and the E/A were still increased, whereas the thickness of anterior wall and the peak velocity of LV outflow were decreased in group A, B, and C after treatment comparing with group E.

CONCLUSION

Both angiotensin converting enzyme inhibitor and angiotensin II receptor antagonist can prevent the ventricular remodeling and improve the ventricular function.

A nonparametric estimator of survival functions for arbitrarily truncated and censored data

It is well-known that the nonparametric maximum likelihood estimator (NPMLE) may severely under-estimate the survival function with left truncated data. Based on the Nelson estimator (for right censored data) and self-consistency we suggest a nonparametric estimator of the survival function, the iterative Nelson estimator (INE), for arbitrarily truncated and censored data, where only few nonparametric estimators are available. By simulation we show that the INE does well in overcoming the under-estimation of the survival function from the NPMLE for left-truncated and interval-censored data. An interesting application of the INE is as a diagnostic tool for other estimators, such as the monotone MLE or parametric MLEs. The methodology is illustrated by application to two real world problems: the Channing House and the Massachusetts Health Care Panel Study data sets.

Sensitive and specific high-performance liquid chromatographic assay with ultraviolet detection for the determination of cocaine and its metabolites in rat plasma

A sensitive, specific and precise HPLC-UV assay was developed to quantitate cocaine (COC) and its metabolites benzoylecgonine (BE), norcocaine (NC) and cocaethylene (CE) in rat plasma. After adding 50 microl of the internal standard solution (bupivacaine, 8 microg/ml) and 500 microl of Sørensen's buffer (pH 6) to 100 microl of rat plasma sample, the mixture was extracted with 10 ml of chloroform. The organic layer was transferred to a clean test tube and was evaporated under nitrogen. The residue was reconstituted in 100 microl of mobile phase and 35 microl was injected onto the HPLC column. The mobile phase consisted of methanol-acetonitrile-50 mM monobasic ammonium phosphate (5:7:63, v/v/v) and was maintained at a flow-rate of 0.4 ml/min. Separation of COC and its metabolites was achieved using a Supelcosil ABZ+plus deactivated reversed-phase column (250x2.1 mm I.D., 5 microm). Calibration curves were linear over the range of 25-5000 ng/ml for COC and its three metabolites. The absolute extraction efficiencies for BE, COC, NC, CE and bupivacaine were 56.6%, 78.6%, 61.1%, 76.4% and 67.0%, respectively. COC and its metabolites were stable in mobile phase for 24 h at room temperature and in rat plasma for 2 weeks at -20degrees C. The limits of detection for BE, COC, NC and CE were 20, 24, 15 and 12.9 ng/ml, respectively. These values correspond to 0.70, 0.84, 0.525 and 0.452 ng of the according compound being injected on column. The within-day coefficient of variation for the four compounds ranged from 3.0% to 9.9% while the between-day precision varied from 3.6% to 14%. This method was used to analyze rat plasma samples after administration of COC alone and in combination with alcohol. The pharmacokinetic profiles of COC and its metabolites in these rats are also described.

The acrAB homolog of Haemophilus influenzae codes for a functional multidrug efflux pump

Disruption of gene HI0894 or HI0895 in Haemophilus influenzae Rd, homologs of Escherichia coli acrAB multidrug efflux genes, caused hypersusceptibility to erythromycin, rifampin, novobiocin, and dyes such as ethidium bromide and crystal violet and increased accumulation of radioactive erythromycin, showing that these genes are expressed and contribute to the baseline level resistance of this organism through active drug efflux. The gene disruption did not produce detectable changes in susceptibility to several other antibiotics, possibly because rapid influx of small antibiotic molecules through the large H. influenzae porin channels counterbalances their efflux.

[Hepatitis B virus DNA detection by means of polymerase chain reaction in patients with chronic hepatitis and hepatocellular carcinoma]

HBV immunological detection and HBV DNA detection by polymerse chain reaction (PCR) or molecular hybridization with 32P labeled probe were done in 61 patients with chronic hepatitis (CH) and 47 patients with hepatocellular carcinoma (HCC) to investigate the relationship between HBV replication and serum markers. The HBV DNA was detected in 90.50% of CH patients and 50.00% of HCC patients with HBsAg, HBeAg and anti-HBc positive; in 45.40% of CH patients and 7.14% of HCC patients with HBsAg, anti-HBe and anti-HBc positive; in 60.00% of CH patients and 40.00% of HCC patients with HBsAg and negative HBeAg, anti-HBe positive; in 20.00% of CH patients and 22.22% of HCC patients with HBsAg negative and anti-HBe or anti-HBe or anti-HBs positive; in 0 of CH or HCC patients lack of HBV serum markers. Our data suggested that the most active HBV replication was correlated to the presence of both HBsAg and HBeAg, there were some extent of HBV replication in CH or HCC patients with positive HBsAg, the inhibition of HBV replication was related to anti-HBe, the less active HBV replication was seen in HCC patients when compared with CH patients.

Tumor necrosis factor-alpha: a neuromodulator in the CNS

In the central nervous system (CNS), the cytokine tumor necrosis factor-alpha (TNF alpha) is produced by both neurons and glial cells, participates in developmental modeling, and is involved in many pathophysiological conditions. There are activity-dependent expressions of TNF alpha as well as low levels of secretion in the resting state. In contrast to the conventional view of a cytotoxic effect of TNF alpha, accumulating evidence suggests a beneficial effect when TNF alpha is applied at optimal doses and at specific periods of time. The bimodal effect is related to subtypes of receptors, activation of different signal transduction pathways, and the presence of other molecules that alter the intracellular response elements such as immediate-early genes. TNF alpha may be an important neuromodulator in development of the CNS, diseases of demyelination and degeneration, and in the process of regeneration. It could induce growth-promoting cytokines and neurotrophins, or it could increase the production of antiproliferative cytokines, nitric oxide, and free radicals, thereby contributing to apoptosis.

Blood-brain barrier permeability to ebiratide and TNF in acute spinal cord injury

Spinal cord injury (SCI) in mammals has a poor outcome because of a lack of regeneration. Alteration of the local environment after injury may induce regeneration. However, the passage of blood-borne or exogenous neurotrophic substances through the blood-brain barrier (BBB) is not well characterized in either normal or injured states. We investigated the permeability of the BBB in normal and injured states to two markers of permeability (albumin and sucrose), to a peptide (ebiratide), and to a cytokine [tumor necrosis factor-alpha(TNF)]. We found that in normal mice the cervical and lumbar areas of the spinal cord were more permeable than the thoracic area and the brain to all four substances. The penetration of the alpha-MSH/ACTH analogue ebiratide and of TNF, substances that have saturable transport systems across the BBB and may be involved in regenerative processes in the CNS, followed a regional pattern of differential permeability comparable to that of albumin and sucrose. Complete transection at the lumbar level induced a temporal change in the permeability of the BBB. The increased permeability, as measured by the radioactively labeled tracers albumin and sucrose, was most apparent in the lumbar region proximal to the transection. After SCI, the permeability to ebiratide remained unchanged, suggesting that disruption of the BBB did not affect the transport system for ebiratide. By contrast, the increase of permeability to TNF exceeded that detected by the markers albumin and sucrose. This enhanced permeability was inhibited by excess unlabeled TNF in the blood, showing saturability. This suggests that the transport system for TNF may be activated in SCI.

Use of an improved method for analysis of urinary aflatoxin M1 in a survey of mainland China and Taiwan

An improved monoclonal antibody immunoaffinity chromatography/high-pressure liquid chromatography/ fluorescence detection method was developed to measure aflatoxin (AF) exposure by quantifying AFM1 in human and rat urine samples. Analysis of different amounts of various AF metabolites showed that the immunoaffinity resin was highly selective for aflatoxin B1 (AFB1), AFB2, and AFM1. Recovery of added AFs increased with the amount of immunoaffinity resin and was virtually complete within the range of 0.01-10 ng of AFM1 by using 7 ml of resin. The detection limit of this method is 0.5 pg/ml urine. Rats dosed with tritiated AFB1 excreted in their urine tritiated AFM1, among other AF metabolites, as indicated by chemical derivative confirmation and cochromatography with authentic AFM1 and agreement of radioactivity and fluorescence quantitation. A linear dose-response relationship was found over the range of 0.05-50 micrograms/kg of body weight/day. Two humans dosed with 1.0 microgram of pure AFB1 excreted 6-7% of the dose as urinary AFM1 over 5-7 days. Pooled urine samples from 30 men from each of 69 rural counties in mainland China and 16 survey areas in Taiwan, with two villages per county or area, were analyzed with this improved method (170 villages total). The correlation coefficient of urinary excretion of AFM1 compared between villages within all 85 survey areas was 0.50 (P < 0.001). Sixty-five % of the samples contained detectable concentrations of AFM1 with an average excretion of 3.1 ng/12 h. Assuming an excretion rate of 2-6%, this AFM1 excretion corresponds to a very low average daily AF consumption of 0.1-0.3 microgram/day (possible range, 0-11 micrograms/day). Patterns of urinary excretion of AFM1 were similar in mainland China and Taiwan.

Permeability of the blood-brain and blood-spinal cord barriers to interferons

Interferons (IFNs) are cytokines that produce effects in the CNS even though their production occurs mainly in the periphery. Direct passage of IFNs from blood to CNS could be an important route by which circulating IFNs exert their central effects. In this report, we characterize the pharmacokinetics of the passage of IFNs through the blood-brain and blood-spinal cord barriers in four separate regions: whole brain and the cervical, thoracic and lumbosacral segments of the spinal cord. We found that the spinal cord had greater permeability to IFNs than did the brain. For each corresponding region, the permeability to IFN alpha was higher than that to IFN gamma. Capillary depletion after cardiac perfusion showed that most of the injected IFN was not entrapped by the vasculature but entered the parenchyma of the brain. HPLC showed that most of the IFN gamma entered in intact form. The passage of radioactively labeled IFN gamma into the brain and cervical spinal cord was saturated by a low dose of unlabeled IFN gamma, while passage into the thoracic and lumbosacral spinal cord was not saturated. In contrast, for another cytokine, tumor necrosis factor alpha (TNF alpha), a saturable transport system was present in distal spinal cord as well as the brain. The results show that IFNs and TNF alpha can enter the CNS from the periphery but with regional differences.

Study of structure-activity correlation in destruxins, a class of cyclodepsipeptides possessing suppressive effect on the generation of hepatitis B virus surface antigen in human hepatoma cells

A new destruxin [destruxin E2 chlorohydrin] was isolated from the culture medium of Metarrhizium anisopliae and its structure was determined by NMR spectroscopy and mass spectrometry. As compared with other destruxins, the new destruxin showed a lower suppressive activity on the production of hepatitis B virus surface antigen in human hepatoma Hep3B cells. NMR study coupled with molecular modeling by computer graphics has revealed that the hydrophobicity nature of the convex surface characteristic of all destruxin molecules plays an important role in their biological activity.

The relationship between surface dust lead loadings on carpets and the blood lead of young children

The final clean-up of residential lead abatement projects in federally-supported housing, as well as in other housing in a number of states, must meet surface dust lead clearance levels expressed as μg of lead per square foot. These clearance levels were established because hand-to-mouth ingestion of lead-contaminated dust is recognised as a major pathway through which many children are exposed. A dilemma exists because many floors in housing undergoing abatement are carpeted and the established clearance levels are generally not recommended for use on carpets. These clearance levels are also used as 'action levels' to determine whether exposure reduction activities are needed. The US Environmental Protection Agency is currently in the process of issuing standards for hazardous levels of lead in interior dust and bare soil under Title X of the Housing and Community Development Act of 1992, 'The Residential Lead-Based Paint Hazard Reduction Act of 1992'. An effort to develop a potential surface dust lead clearance level for carpets was made using an existing vacuum dust collection method that has previously been shown to be a reliable indicator of childhood lead exposure. This method was designed for use on carpeted and non-carpeted surfaces. Using data from the Cincinnati Soil Lead Abatement Demonstration Project, the suggested floor-dust lead level where an estimated 95% of the population of children would be expected to have blood lead values below the national goal of 10 μg dL(-1), was more than an order of magnitude lower than the current floor-dust lead clearance level of 1080 μg m(-2) (100 μg ft(-2)). Further comparisons of blood lead and carpet lead levels in other parts of the country should be performed before a risk-based lead loading clearance level is established.

Regulation of rat liver glucose-6-phosphatase gene expression in different nutritional and hormonal states: gene structure and 5'-flanking sequence

The mRNA level of the catalytic subunit of rat liver glucose-6-phosphatase (Glu-6-Pase) was regulated by hormones commensurate with activity changes in vivo. Insulin exerts a dominant negative effect on the mRNA levels of Glu-6-Pase. Both mRNA levels and activities of the enzyme are low in the fed and refed state where insulin levels are elevated. Insulin administration to diabetic rats also decreases levels of mRNA and Glu-6-Pase activity. Insulin at a concentration of 1 nmol/l completely overcomes the stimulatory effect of glucocorticoids on Glu-6-Pase message levels in FAO hepatoma cells. The stimulatory response to glucocorticoid in FAO cells is biphasic, with maxima seen at 3 and 18 h after hormone addition (respectively 1.6- and 3.3-fold). 8-(4-chlorophenylthio)-cAMP (CPT-cAMP) causes a fourfold increase in Glu-6-Pase mRNA at 3 h in FAO cells. The gene of rat liver Glu-6-Pase is 13 kilobases in length and comprised of 5 exons. The exon-intron structure is completely conserved when compared with the mouse and human genes. A 0.5-kb 3'-untranslated region, which is present in rat and mouse liver Glu-6-Pase cDNA, is absent in the Glu-6-Pase gene reported here, indicating the possible duplication of either the terminal fifth exon or the entire gene. The promoter region contains a consensus core CCAAT element at position -207 and a TATAAA at position -31. Several possible response elements have been identified in the 5'-flanking region (from a HindIII site at position -1641). A consensus glucocorticoid response element is located at base pair -1552, a 9/10 match of the insulin response sequence is located at position -1449, and a 7/8 match of the cAMP response element is located at position -164.

Renal gluconeogenesis and blood flow during endotoxic shock

OBJECTIVES

To determine whether endotoxic shock decreases the renal gluconeogenic capacity and the renal artery blood flow.

METHODS

An in-vivo, murine, nonrecirculating kidney perfusion model was studied in a trauma research laboratory. Each of 12 fasted, male Holtzman rats (shock n = 6, control n = 6) was injected with 1 mL of normal saline or endotoxin (20 mg/kg). Five hours after the injection, all the rats were anesthetized and blood samples were obtained for the determination of the plasma glucose. Right renal artery blood flow was measured by an ultrasonic small-animal flow meter. The kidney was then perfused via the renal artery with 37 degrees C, oxygenated, glucose-free Krebs-Henseleit solution in the presence of 100 mumol of phloridzin to inhibit the cellular uptake of glucose. Renal glucose production was determined by measuring glucose in both renal vein effluent and urine. After 30 minutes of equilibration, 5 mmol of lactate and 0.5 mmol of pyruvate were added to the perfusate as a gluconeogenic substrate. Renal vein and ureteral effluent samples were collected after 5, 10, and 15 minutes.

RESULTS

The endotoxic shock group showed hypoglycemia (p < 0.05) as well as a decrease in renal artery blood flow (p < 0.05). Gluconeogenic stimulation was demonstrable in both the control and the endotoxic shock groups after 15 minutes of perfusion with substrate (p < 0.05). However, renal gluconeogenesis was significantly attenuated in the endotoxic shock group compared with the control.

CONCLUSIONS

Renal glucose production in response to a gluconeogenic substrate is significantly attenuated during the hypoglycemic phase of endotoxic shock. Endotoxic shock also causes a significant decrease of renal artery blood flow.

Differential permeability of the BBB in acute EAE: enhanced transport of TNT-alpha

Impairment of the blood-brain barrier (BBB) in experimental autoimmune encephalomyelitis (EAE) has been frequently attributed to disruption, without much consideration of saturable transport processes. In mice with EAE, we studied the permeability of the BBB to radioactively labeled albumin and sucrose, markers of BBB disruption, and tumor necrosis factor-alpha (TNF-alpha), a cytokine transported across the BBB by a saturable system and thought to play a role in the pathogenesis of EAE. Permeation of the BBB was increased to all three substances during the acutely ill stage, was greatest in the lumbar spine, and returned to normal with recovery. The change in BBB permeability to sucrose was greater than to the larger albumin and is consistent with a partial disruption of the BBB. The enhanced permeability to TNF-alpha was comparable to that for sucrose, even though TNF-alpha is similar in size to albumin. This paradoxically high uptake of TNF-alpha could be explained by an enhancement of its endogenous saturable transport system. Thus the changes in BBB function during EAE extend beyond disruption to include changes in the saturable transport systems for substances involved in the disease process.

DNA segments sensitive to single-strand-specific nucleases are present in chromatin of mitotic cells

It was observed before that DNA in situ in chromatin of mitotic cells is more sensitive to denaturation than DNA in chromatin of interphase cells. DNA sensitivity to denaturation, in these studies, was analyzed by exposing cells to heat or acid and using acridine orange (AO), the metachromatic fluorochrome which can differentially stain double-stranded (ds) vs single-stranded (ss) nucleic acids, as a marker of the degree of DNA denaturation. However, without prior cell treatment with heat or acid no presence of single-stranded DNA in either mitotic or interphase cells was detected by this assay. In the present experiments we demonstrate that DNA in situ in mitotic cells, without any prior treatment that can induce DNA denaturation, is sensitive to ss-specific S1 and mung bean nucleases. Incubation of permeabilized human T cell leukemic MOLT-4, promyelocytic HL-60, histiomonocytic lymphoma U937 cells, or normal PHA-stimulated lymphocytes with S1 or mung bean nucleases generated extensive DNA breakage in mitotic cells. DNA strand breaks were detected using fluorochrome-labeled triphosphonucleotides in the reaction catalyzed by exogenous terminal deoxynucleotidyl transferase. Under identical conditions of the cells' exposure to ss-specific nucleases, DNA breakage in interphase cells was of an order of magnitude less extensive compared to mitotic cells. The data indicate that segments of DNA in mitotic chromosomes, in contrast to interphase cells, may be in a conformation which is sensitive to ss nucleases. This may be a reflection of the differences in the torsional stress of DNA loops between interphase and mitotic chromatin. Namely, greater stress in mitotic loops may lead to formation of the hairpin-loop structures by inverted repeats; such structures are sensitive to ss nucleases. The present method of detection of such segments appears to be more sensitive than the use of AO. The identification of mitotic cells based on sensitivity of their DNA to ss nucleases provides an additional method for their quantification by flow cytometry.

Isolation of virus-neutralizing RNAs from a large pool of random sequences

RNA and ribonuclease-resistant RNA analogs that bound and neutralized Rous sarcoma virus (RSV) were isolated from a large pool of random sequences by multiple cycles of in vitro selection using infectious viral particles. The selected RNA pool of RSV-binding sequences at a concentration of 0.16 microM completely neutralized the virus. Of 19 sequences cloned from the selected pool, 5 inhibited RSV infection. The selected RNA and RNA analogs were shown to neutralize RSV by interacting with the virus, rather than by adversely affecting the host cells. The selection of the anti-RSV RNA and RNA analogs by intact virions immediately suggests the potential application of this approach to develop RNA and RNA analogs as inhibitors of other viruses such as human immunodeficiency virus.

Phosphorylation of F1F0 ATPase delta-subunit is regulated by platelet-derived growth factor in mouse cortical neurons in vitro

The delta subunit of F1F0 ATPase (ATP synthase complex) is part of the stalk connecting the F1 and F0 moieties. Studies in Escherichia coli suggest that the analogous bacterial subunit, called epsilon, is essential for the ATPase assembly energy coupling. Platelet-derived growth factor (PDGF) is an important growth factor for various cell types, including neurons of the CNS. Using two-dimensional gel electrophoresis, microsequencing, western blot analysis, and immunoprecipitation techniques, we have found that PDGF induces phosphorylation of the delta subunit or a closely related peptide in cultured mouse cortical neurons.

Synthesis and application of hepatitis E virus peptides to diagnosis

Based on computer analysis of hydrophobicity and prediction of secondary structures for the full-length putative proteins encoded by open reading frame-1 (ORF-1), ORF-2 and ORF-3 of hepatitis E virus (HEV), we selected antigenic regions with hydrophilicity, beta-turn, and beta-sheet, and synthesized 7 peptides of possible epitope-containing regions of the polypeptide encoded by all 3 ORFs of HEV genomic RNA by Merrifield's method of solid-phase synthesis. The synthetic peptides were screened and identified by solid-phase enzyme-linked immunosorbent assay (ELISA). Three of the peptides (EH174 from ORF-1, EH286 from ORF-2 and EH362 from ORF-3) showed antigenic activity and possible application for the development of anti-HEV test kits (the peptide-based ELISA). The laboratory experiments and clinical trials showed that the kits, using a set of 3 synthetic HEV peptides as coating antigens, were of high specificity and exhibited good reproducibility. The small-scale seroepidemiological survey indicated high seroprevalence (14.3%) of anti-HEV in Tibetan populations. Additionally, the results also demonstrated good agreement with clinical findings, suggesting that the test kits will be of major use for immunodiagnosis and seroepidemiological surveys of HEV infection.

Recommendations for initial antibiotic treatment of extracavitary arterial graft infections

BACKGROUND

Initial antibiotic treatment of extracavitary arterial graft infections is usually empiric or based on Gram's stain findings. Increasing virulence of bacteria causing extracavitary arterial graft infections may render previous choices of antibiotics obsolete. The purposes of this study were to correlate Gram's stain findings of gram-positive bacteria and gram-negative bacteria with wound cultures and provide a microbiologic basis for appropriate initial antibiotic therapy.

METHODS

Between July 1, 1979 and June 30, 1994, specimens obtained on the day of admission from purulent wounds involving 113 extracavitary arterial graft infections were retrospectively reviewed for Gram's stain and culture and sensitivity results.

RESULTS

Gram's stain findings correlated with final cultures on only 28 of 113 cases (25%), including 20 of 48 pure gram-positive, 2 of 24 pure gram-negative, and 6 of 41 mixed bacterial cultures. Staphylococcus aureus was the most common gram-positive bacteria cultured (43 isolates) and Pseudomonas species was the most common gram-negative bacteria (25 isolates). Bacteria were sensitive to a first-generation cephalosporin in only 32% (36 of 113) of infections. A combination of vancomycin and either ticarcillin-clavulanic acid or ceftazidime, which have minimal toxicity and provide excellent coverage against staphylococci, Pseudomonas, and other gram-negative bacteria, would have covered 96% (109) and 95% (107) of cultured organisms, respectively.

CONCLUSIONS

Regardless of Gram's stain findings, current recommendations for initial treatment of extracavitary arterial graft infections should include vancomycin and ceftazidime or ticarcillin-clavulanic acid until final culture and sensitivity results dictate the use of more selective antibiotics.

Alterations in hepatic production and peripheral clearance of IGF-I after endotoxin

Lipopolysaccharide (LPS) produces a rapid and sustained reduction in the circulating concentration of insulin-like growth factor I (IGF-I), which may be responsible, in part, for the alterations in protein metabolism observed in these animals. The purpose of the present study was to determine whether this drop was due to a decreased hepatic production of IGF-I and/or an increased clearance of the peptide from the blood. Four hours after intravenous injection of LPS the plasma IGF-I concentration was decreased 50%. IGF-I release by in situ perfused livers from control rats was constant throughout the 60-min perfusion period and averaged 111 +/- 3 ng/min. In contrast, hepatic IGF-I output was decreased 46% by in vivo LPS. In contrast, livers from LPS-injected rats released more IGF binding proteins-1, -2 and -4 than did control livers. Hepatic cell isolation indicated that LPS decreased the IGF-I content in Kupffer and parenchymal cells, but not endothelial cells, by approximately 45%. Pharmacokinetic analysis of blood 125I-IGF-I decay curves indicated that the half-life for whole body clearance of 125I-IGF-I from the circulation was not altered by LPS. However, LPS increased 125I-IGF-I uptake by spleen, liver, lung, and kidney while decreasing uptake by the pancreas and gastrointestinal tract. These results indicate that the LPS-induced decrease in blood IGF-I concentration is primarily due to a reduction in hepatic production, not a change in whole body peptide clearance, and that a decreased production by both parenchymal and Kupffer cells contributes to this alteration.