Transdermal nicotine suppresses cutaneous inflammation

BACKGROUND

Cigarette smoking significantly alters the inflammatory response in the skin following application of irritants and rubefacients. The mechanism of this effect is unknown. There are thousands of components in cigarette smoke that may be pharmacologically important, but there is evidence to suggest that nicotine may play an important role in the observed effect on the inflammatory process.

DESIGN

This was an interventional study to assess cutaneous responsiveness to different stimuli after transdermal nicotine administration in volunteer subjects. Cutaneous testing was performed at baseline and at weeks 2 and 4 (the end) of the study.

SETTING

The department of Dermatology, University Hospital of Wales, Cardiff.

PARTICIPANTS

Ten lifelong nonsmokers were recruited for the study.

INTERVENTION

Nicotine patches were applied daily for 1 month.

MAIN OUTCOME MEASURES

The following tests were performed: application of 2 times the minimal irritancy dose of sodium lauryl sulfate, irradiation with 2 times the minimal erythema dose of UV-B, measurement of cutaneous vasodilation following application of ethyl and hexyl nicotinate, and reactive hyperemia following arterial occlusion.

RESULTS

There was a significant reduction in the cutaneous inflammatory response to sodium lauryl sulfate (P < .001) and irradiation with UV-B (P < .003) and a reduction in reactive hyperemia (P < .03) after 2 weeks of treatment, which returned values to normal at 4 weeks. There was no change in blood flow following application of topical nicotinates.

CONCLUSIONS

Nicotine administration via a transdermal delivery system suppresses the cutaneous inflammatory response to sodium lauryl sulfate and UV-B, as well as triggers a transient suppression of reactive hyperemia following arterial occlusion. The apparent anti-inflammatory effects of smoking cigarettes can therefore only partially be explained as a long-term effect of nicotine.

Mutations in cholesteryl ester transfer protein and hepatic lipase in a North American population

OBJECTIVE

To examine a North American population sample with increased HDL cholesterol for mutations in the genes coding for cholesteryl ester transfer protein (CETP) and hepatic lipase (HL).

DESIGN AND METHODS

Seventy individuals with increased HDL cholesterol at the time of initial presentation to the Lipid Clinic (males > 1.7 mmol/L, females > 1.8 mmol/L) were examined by polymerase chain reaction-restriction fragment length polymorphism (PCR/RFLP) analysis for known mutations in CETP intron 14 and exon 15 and HL exons 6 and 8.

RESULTS

CETP intron 14 mutation frequency 0.7%, CETP exon 15 A1503G 0%, HL exon 6 C873T 2.1%, HL exon 8 C1221T 0%. An unusual mutation in CETP exon 15 G1533A was found at a frequency of 3.5%. The sequence of this mutation was determined to be a G to A change at bp 1533 resulting in a predicted amino acid change of arginine to glutamine at position 451.

CONCLUSIONS

Known mutations in CETP were much less prevalent in this North American population than in the Japanese populations that have been previously reported. HL mutations, described previously in only 6 families worldwide, appear to be more prevalent than previously recognized. CETP G1533A, reported only once previously is prevalent in this population at a surprisingly high frequency. The functional significance of this mutation is unknown.

Identification and characterization of thymidylate synthase from Neisseria gonorrhoeae

Thymidylate synthase converts deoxyuridylate to deoxythymidylate. The thyA gene has been cloned and sequenced from Neisseria gonorrhoeae MS11. This gene has an open reading frame of 795-801 bp and encodes a product which shares 71% identity with its Escherichia coli homolog. Unlike its E. coli counterpart, gonococcal thyA has a large, upstream transcribed region (300+ bp) that lacks a translatable reading frame. Gonococcal thyA is capable of complementing an E. coli thyA null mutant and shares similar levels of sensitivity with trimethoprim.

Combretastatin A-4, an agent that displays potent and selective toxicity toward tumor vasculature

Selective induction of vascular damage within tumors represents an emerging approach to cancer treatment. Histological studies have shown that several tubulin-binding agents can induce vascular damage within tumors but only at doses approximating the maximum tolerated dose, which has limited their clinical applicability. In this study, we show that the combretastatin A-4 prodrug induces vascular shutdown within tumors at doses less than one-tenth of the maximum tolerated dose. In vitro studies indicate that a short drug exposure results in profound long-term antiproliferative/cytotoxic effects against proliferating endothelial cells but not cells that are quiescent prior to and during drug exposure. Vascular shutdown, within experimental and human breast cancer models in vivo following systemic drug administration, was demonstrated with a reduction in functional vascular volume of 93% at 6 h following drug administration and persisted over the next 12 h, with corresponding histology consistent with hemorrhagic necrosis resulting from vascular damage. These actions against tumor vasculature and the broad therapeutic window demonstrate the clinical potential of these drugs and warrant further study to elucidate the mechanisms responsible for the antivascular effects of combretastatin A-4.

Single-strand DNA intermediates in phage lambda's Red recombination pathway

An assay was developed to assess early intermediates arising in lambda's Red recombination pathway. Double-strand breaks were delivered in vivo to nonreplicating lambda chromosomes. Analysis by blot hybridization of total DNA extracts revealed the following: (i) long (>1.4 kilobases) single-strand DNA (ssDNA) intermediates; (ii) resection proceeding bidirectionally from the break site; (iii) single-strand overhangs of 3' polarity; and (iv) in the absence of lambda's ninR functions, a requirement of the red alpha gene product for the production of ssDNA. Therefore, the physical characteristics exhibited by these ssDNA molecules are consistent with their being an early recombination intermediate in the Red recombination pathway as proposed previously from genetic and in vitro biochemical analyses.

Measurement of tumor oxygenation: a comparison between polarographic needle electrodes and a time-resolved luminescence-based optical sensor

A novel oxygen sensor which does not rely on electrochemical reduction has been used to measure the oxygenation of the murine sarcoma F in a comparative study with an existing polarographic electrode that is available commercially. The prototype luminescence sensor yielded an oxygen distribution comparable with readings made using a pO2 histograph. The percentage of regions detected that had a pO2 less than 5 mm Hg was 79 and 75 using the Eppendorf pO2 histograph and the luminescence fiber optic sensor, respectively. These values were compatible with a measured radiobiologically hypoxic fraction of 67% in this tumor. The polarographic method detected more regions with a pO2 of 2.5 mm Hg or less (69%) compared with the optical sensor (50%) (P < 0.05). This could reflect differences in the oxygen use of the sensing devices. This initial assessment indicates the potential of a fiber-optic-based oxygen-monitoring system. Such a system should have several advantages including monitoring temporal oxygen changes in a given microregion and use with NMR procedures.

Metabolic and clonogenic consequences of ischaemia reperfusion insult in solid tumours

Tumour cell survival is intimately related to blood vessel function and so the tumour vasculature represents a novel target for cancer therapy. We have investigated a murine tumour model in which a metal clamp was used to occlude the vascular supply temporarily and then removed to allow reperfusion. This allows the study of ischaemia-reperfusion as a model system for investigating tumour response to metabolic and oxidative stress. Recent studies have shown that prolonged reduction of tumour blood flow results in a deterioration of the hypoxic and acidic microenvironment found within tumours which leads to cytotoxicity. This cytotoxicity is dramatically enhanced if these cells are subsequently reperfused. It was the aim of the present study to determine the relative contribution of cytotoxicity occurring during the ischaemic period and that occurring during reperfusion. Although significant reductions in tumour energy status were induced during the clamping period itself, these were poorly correlated with the degree of tumour cytotoxicity. Relative vascular perfusion, measured using a radiolabelled tracer, remained significantly depressed below the control value following clamp removal. The degree of recovery of perfusion was also dependent upon the clamp duration. Relative tumour perfusion at 1 h after clamp removal was 70.1 +/- 14.6 and 50.5 +/- 6.3% of control values after a 1 or 3 h clamp, respectively, and showed no significant further increase when measured at 24 h after clamp removal. Tumour cytotoxicity following ischaemia reperfusion insult was modulated by administering the anti-oxidant enzymes superoxide dismutase or catalase intravenously just before clamp removal. These enzymes are restricted to the vascular compartment, where it is proposed that they modulate the concentration of oxygen free radicals released during reperfusion and by neutrophil oxidative burst. Reperfusion injury to the tumour was enhanced by administration of an inhibitor of nitric oxide synthase, nitro-L-arginine, probably owing to enhanced neutrophil adhesion and oxidative burst. Conversely, reperfusion injury to the tumour was reduced by administration of a nitric oxide donor, diethylamine nitric oxide. The murine model reported in this paper shows that ischaemia-reperfusion damage mediated by oxygen free radical formation provides a model system for investigating tumour response to oxidative stress at the level of the vascular endothelium.

Integration host factor is a transcriptional cofactor of pilE in Neisseria gonorrhoeae

Integration host factor (IHF) is a small, heterodimeric DNA-binding protein with pleiotropic function. IHF was purified to apparent homogeneity from Neisseria gonorrhoeae. Gel-retardation assays demonstrated binding of IHF to the pilE promoter region. The IHF-binding site was identified by DNase I protection assays and mapped proximal to three previously defined pilE promoters. Removal of the putative IHF-binding domain from pilE promoter DNA negated retardation of the DNA fragment when assessed by gel-shift analysis. Kleinschmidt electron microscopy showed pronounced kinking of pilE promoter DNA following incubation with IHF. Isogenic N. gonorrhoeae strains were constructed that contained either a wild-type pilE locus or a deleted pilE locus where the IHF-binding domain was removed. Primer-extension analysis and Northern blotting of total gonococcal RNA showed that in the absence of IHF binding at the pilE promoter, transcription was reduced 10-fold. Together, these data indicate that IHF is a transcriptional co-activator of pilE.

Effect of carbogen breathing on tumour microregional blood flow in humans

BACKGROUND AND PURPOSE

Carbogen is currently being re-evaluated as a radiosensitiser. It acts primarily by increasing tissue pO2, although there is evidence to suggest that enhanced tumour blood flow may also be a component of its action.

MATERIALS AND METHODS

Ten tumours in eight patients with advanced malignant disease were studied. Up to six microprobes, each with an estimated sampling volume of 10(-2) mm3, were inserted into the tumours. Ten min of baseline readings were taken prior to a 10 min carbogen (95% O2/5% CO2) breathing period, measurements were continued for a further 10 min.

RESULTS

The results show that in 34 microregions analysed no overall change in tumour perfusion was seen with carbogen breathing. Individual tumour analysis demonstrated variation in response between patients to carbogen-after 6 min of carbogen four tumours showed an increase in blood flow by more than 10% of the pre-breathing value, two a decrease and four no change. The magnitude of change was small, with only two tumours fluctuating by more than 25%.

CONCLUSIONS

These findings confirm the presence of transient fluctuations in microregional blood flow in human tumours but suggest that the radiosensitising action of carbogen lies primarily in its effect on increasing the oxygen capacity of blood. This supports the addition of agents such as nicotinamide with carbogen in order to overcome both diffusion and perfusion limited hypoxia.

Effect of nitro-L-arginine on blood flow, oxygenation and the activity of hypoxic cell cytotoxins in murine tumours

This study was an investigation into the ability of nitro-L-arginine to change blood flow, oxygenation status and the activity of hypoxic cell cytotoxic agents in two different transplanted murine tumours. The tumour models were the C3H mammary carcinoma grown in the feet of female CDF1 mice and the SaF grown on the backs of CBA mice. Treatments were carried out in restrained non-anaesthetised animals when tumours were about 100 to 200 mm3 in size. Blood flow was monitored using laser Doppler flowmetry; oxygen partial pressure (pO2) distributions were obtained with an Eppendorf oxygen electrode; and response to treatment with hyperthermia (43.5 degrees C; 30 min) and RB6145 (250 mg kg-1;i.p.) assessed using a tumour growth delay assay. Nitro-L-arginine (10 mg kg-1; i.v.) significantly reduced blood flow by around 40-60% within 15 min after injection in C3H tumour and by 30 min in the SaF. However, nitro-L-arginine had absolutely no effect on tumour pO2 measured at the time of maximal blood flow reduction in both tumour types. It also failed to enhance the response of the C3H tumour to heat, but did produce a small yet significant increase in the response of the SaF tumour to RB6145.

Antivascular approaches to solid tumour therapy: evaluation of tubulin binding agents

We have assessed the vascular effects of vinblastine and four other tubulin binding agents (dolastatin 10, dolastatin 15, combretastatin A1 and combretastatin A4), which are awaiting clinical evaluation. All five agents induce a reduction in tumour blood flow as measured by uptake of RbCI 24 h post drug administration. The degree of reduction ranged from 50% with combretastatin A1 to 90% with dolastatin 10. These reductions were similar to that seen with flavone acetic acid (FAA) and indicate that antivascular effects are a common feature of tubulin binding agents. We subsequently evaluated whether the blood flow reductions, induced by FAA and vinblastine, could be used to enhance the activity of the bioreductive drug tirapazamine. Since the kinetics and extent of blood flow reductions induced by the agents is comparable, similar therapeutic response was expected. Potentiation was only evident with FAA, indicating that this effect is not directly related to killing of hypoxic tumour cells induced as a consequence of blood flow reduction.

Microregional blood flow in murine and human tumours assessed using laser Doppler microprobes

A multichannel laser Doppler system has been used to measure microregional fluctuations in perfusion in the HT29 human tumour xenograft and in patients with advanced malignant disease. A comparison is made with previously obtained data for the SaF, a transplantable murine tumour. The 300 microns diameter probes recorded fluctuations in erythrocyte flux in tumour microregions with an estimated volume of 10(-2) mm3. Of the 66 human tumour microregions sampled, 26% showed a change in erythrocyte flux by a factor of 2 or more over the 60 min measurement period, compared with 37% of HT29 and 48% of SaF microregions. In each of the studies more than 50% of changes were completed within 20 min, although slower changes were more common in the human tumours than in the experimental systems. Within the 1 h monitoring period at least 30% of the changes were reversed (human tumours 30%, HT29 45%, SaF 31%). These findings demonstrate that microregional changes in erythrocyte flux, consistent with transient, perfusion-driven changes in oxygenation, are a feature of human malignancies as well as experimental transplanted tumours.

Microregional fluctuations in perfusion within human tumours detected using laser Doppler flowmetry

PURPOSE

Transient fluctations in erythrocyte flux consistent with perfusion driven hypoxia have been previously reported using experimental tumour models. The present study was designed to establish whether such changes are a common feature of human tumours.

METHODS AND MATERIALS

A multi-channel laser Doppler system was used to monitor microregional changes in flow in human tumours. Eight individual tumours were investigated, two primary and one locally recurrent breast carcinoma, two metastatic skin deposits and three metastatic lymph nodes. Six custom designed microprobes (diameter of 300 microns), each monitoring a nominal sampling volume of approximately 10(-2) mm3 were inserted into the tumour and perfusion monitored over a period of 60 min.

RESULTS

The results show that in 54% of the regions monitored there was a change in microregional blood flow by a factor of 1.5 or more. Over the whole 60-min period, 19% of the changes were reversed, with a time course of 4-44 min.

CONCLUSIONS

This finding demonstrates that microregional fluctuations in perfusion occur frequently in human tumours. Furthermore, the observation that 19% of the changes were reversed implies that at least some of the cells are subject to transient acute hypoxia.

Differential mechanisms targeting type 1 plasminogen activator inhibitor and vitronectin into the storage granules of a human megakaryocytic cell line

Type 1 plasminogen activator inhibitor (PAI-1) and its cofactor vitronectin (Vn) are stored within the alpha-granules of platelets. The two possible sources for their biosynthetic origin are endogenous synthesis in megakaryocytes or endocytosis from plasma. Using ultrastructural and confocal laser scanning microscopic (CLSM) image analysis, we observed that treatment of Dami cells, a human megakaryocytic cell line, with phorbol myristate acetate (PMA) induces the accumulation of PAI-1 and Vn in intracellular storage vacuoles that contain other alpha-granule proteins such as von Willebrand factor. To examine evidence for biosynthesis of PAI-1 and Vn by Dami cells, we immunoprecipitated PAI-1 and Vn from the conditioned media of cells biosynthetically radiolabeled with 35S-methionine in the presence or absence of PMA. In contrast to Hep G2 cells, which synthesize both PAI-1 and Vn, only 35S-PAI-1 was recovered from PMA-treated Dami cells. Reverse transcription-PCR analysis of RNA extracted from resting and PMA-treated Dami cells confirmed that PAI-1 mRNA expression was detectable at low levels in resting cells and induced by PMA treatment. In contrast, Vn mRNA was not detected. We examined binding and internalization (endocytosis) of PAI-1 and Vn by Dami cells using biotinylated analogs (b-PAI-1 and b-Vn). Flow cytometry analysis indicated that the binding of b-Vn to Dami cells was dose-dependent, saturable, and specific for multimeric forms of Vn. Cells were incubated at 4 degrees C or 37 degrees C and endocytosis of b-Vn was shown by probing electrophoretically fractionated cell lysates with 125I-labeled streptavidin. Only cells incubated at 37 degrees C internalized b-Vn. CLSM image analysis confirmed that the b-Vn was internalized and that it colocalized with PAI-1 in storage granules. The binding of b-Vn to cells was inhibited by the presence of PAI-1, and there was no evidence of specific b-PAI-1 binding or uptake to resting or PMA-treated cells. These data suggest that accumulation of PAI-1 in Dami cell storage granules is due to endogenous synthesis and that the accumulation of Vn is due to endocytosis of serum-derived Vn.

Limited variation and maintenance of tight genetic linkage characterize heteroallelic pilE recombination following DNA transformation of Neisseria gonorrhoeae

Genetic recombination impacts on neisserial biology in two ways: (i) specific loci undergo rearrangement at high frequency leading to the formation of many different alleles; and (ii) Neisseria, being naturally competent for DNA transformation, provide a means to disseminate the novel alleles throughout a population. In this study pilE was used as a model system to examine heteroallelic recombination following DNA transformation. When gonococci were transformed with chromosomal donor DNA containing different pilE alleles, the majority of pilE recombinants arose through allelic replacement. Co-conversion analysis across pilE showed that in approximately 85-90% of recombination events encompassing pilE and an adjacent opa locus, linkage was maintained (i.e. approximately 10-15% of recombination events terminated within the approximately 1000 base pair pilE/opaE interval). In addition to those recombinants that arose through allelic replacement, a large pilus-minus subpopulation was also observed (approximately 10% of all recombinants), indicating that many recombination events did not yield recombinant pilEs that could be assembled into functional pili. PilE mosaics increased following transformation with plasmid donor DNAs carrying pilE with limited flanking-sequence homology, suggesting a potential role for flanking-sequence homologies in mosaic formation. Overall, the data support the view that horizontal transmission of chromosomal DNA between gonococci will favour the spread of intact alleles, as opposed to expanding the allelic repertoire through the formation of gene mosaics.

Ischemia reperfusion injury in tumors: the role of oxygen radicals and nitric oxide

Oxidative stress is a key process involved in the action of several therapeutic modalities used in cancer treatment. Ischemia reperfusion insult provides a model system for investigating the processes involved in determining the sensitivity of tumor tissue to oxidative stress. We have investigated the response of the murine CaNT tumor to ischemia reperfusion injury and the role that oxygen radicals and nitric oxide may play in this phenomenon. Our results show that little or no cell kill is detected in tumors exposed to up to 3 h of ischemia if the tumors are excised immediately before reperfusion. However, if reperfusion is permitted, then extensive cell kill is evident 24 h later. i.v. administration of superoxide dismutase or catalase, at the time when vascular reperfusion occurred, resulted in a significant protection against tumor cell kill, suggesting that the damage was mediated by oxygen radicals. Conversely, administration of an inhibitor of nitric oxide synthase, N omega-nitro-L-arginine, resulted in potentiation of tumor cell damage. Administration of a nitric oxide (NO) donor, diethylamine NO, at the time when vascular reperfusion occurred resulted in significant protection against tumor damage. These results suggest that nitric oxide is a potent mediator in determining tumor damage after ischemia reperfusion injury. The role of intrinsic NO production by murine tumors was investigated by measuring the accumulation of nitrate in the medium of tumor explants cultured in vitro in two tumors with differing sensitivity to ischemia reperfusion damage. The clamp-insensitive tumor SaS showed a greater nitrate accumulation than the clamp-sensitive tumor CaNT, which may confer a greater capacity for preventing tumor and endothelial cell damage after oxidative stress.

Pharmacokinetics and binding of the bioreductive probe for hypoxia, NITP: effect of route of administration

The novel compound 7(-)[4'-(2-nitroimidazol-l-yl)-butyl]-theophylline (NITP) can be used as an immunologically detectable probe for hypoxic cells. Because of the limited water solubility of NITP, it has been administered dissolved in peanut oil with 10% dimethylsulphoxide (DMSO). A new aqueous formulation has been devised, based on a 50% solution of a modified beta-cyclodextrin (Molecusol HPB), which increases the water solubility of NITP 10-fold. The pharmacokinetics of NITP in plasma and tumours have been compared following oral and intraperitoneal (i.p.) administration of the NITP in Molecusol, i.p. administration of NITP dissolved in peanut oil + 10% DMSO and injection of a near-saturated aqueous solution of the drug intravenously via the tail vein or i.p. or directly into the tumours. Binding of the marker to hypoxic cells within tumours was also measured after the different routes of administration. The Molecusol vehicle was unexpectedly toxic when administered i.p., but there was no toxicity from NITP dissolved in Molecusol when administered orally. Binding of the drug within tumours was seen for both the peanut oil + 10% DMSO and Molecusol formulations and for both oral and intraperitoneal routes. Binding of NITP within tumours has also been observed following direct injection of the drug, with minimal whole-body exposure to NITP. However, the bound metabolites of NITP within tumours were localised to the injection site, suggesting that direct injection is unlikely to be a useful method of administering bioreductive hypoxia markers. The data in this paper demonstrate that bound metabolites of the hypoxia marker NITP can be detected in tumours following oral administration of an aqueous formulation of NITP, and suggest that oral administration could be a satisfactory administration route for clinical studies with NITP.

Abdominal wall haematoma mimicking visceral injury: the role of CT scanning

Four patients are presented who were thought to have sustained visceral injury following blunt abdominal trauma. However, CT demonstrated abdominal wall haematomata and allowed nonoperative management. Similarity between the clinical findings in visceral injury and abdominal wall haematoma can lead to diagnostic difficulty. The cases illustrate the need to consider abdominal wall haematoma as a possible diagnosis in patients with blunt abdominal trauma. The place of CT in making this diagnosis is highlighted.

Bone fractures in children undergoing orthotopic liver transplantation

This retrospective study documents the incidence and distribution of fractures in 117 children with end-stage liver disease who underwent orthotopic liver transplantation (OLT) over a 6-year period (1987-1993). Both the pre- and post-OLT phases were included. Nineteen children (16.2 %) sustained a total of 69 fractures. Age at time of fracture ranged from 3 months to 9 years 8 months (median 13.5 months). There was no documented trauma in 14/19 cases. Metabolic bone disease, assessed qualitatively on plain radiographs, was present in 17/19 children at the time of fracture. This took the form of rickets (n = 3), osteopenia (n = 12) and osteosclerosis (n = 2). Potential risk factors including pre-existing metabolic bone disease, drugs and immobilization were assessed. The findings emphasise the need for clinical and radiological awareness of the fracture risk, particularly during the peri-transplant period when this risk may be greatest.

Insulin and insulin-like growth factor-I enhance human skeletal muscle protein anabolism during hyperaminoacidemia by different mechanisms

Insulin inhibits proteolysis in human muscle thereby increasing protein anabolism. In contrast, IGF-I promotes muscle protein anabolism principally by stimulating protein synthesis. As increases or decreases of plasma amino acids may affect protein turnover in muscle and also alter the muscle's response to insulin and/or IGF-I, this study was designed to examine the effects of insulin and IGF-I on human muscle protein turnover during hyperaminoacidemia. We measured phenylalanine balance and [3H]-phenylalanine kinetics in both forearms of 22 postabsorptive adults during a continuous [3H] phenylalanine infusion. Measurements were made basally and at 3 and 6 h after beginning a systemic infusion of a balanced amino acid mixture that raised arterial phenylalanine concentration about twofold. Throughout the 6 h, 10 subjects received insulin locally (0.035 mU/min per kg) into one brachial artery while 12 other subjects were given intraaterial IGF-I (100 ng/min per kg) to raise insulin or IGF-I concentrations, respectively, in the infused arm. The contralateral arm in each study served as a simultaneous control for the effects of amino acids (aa) alone. Glucose uptake and lactate release increased in the insulin- and IGF-I-infused forearms (P < 0.01) but did not change in the contralateral (aa alone) forearm in either study. In the aa alone arm in both studies, hyperaminoacidemia reversed the postabsorptive net phenylalanine release by muscle to a net uptake (P < 0.025, for each) due to a stimulation of muscle protein synthesis. In the hormone-infused arms, the addition of either insulin or IGF-I promoted greater positive shifts in phenylalanine balance than the aa alone arm (P < 0.01). With insulin, the enhanced anabolism was due to inhibition of protein degradation (P < 0.02), whereas IGF-I augmented anabolism by a further stimulation of protein synthesis above aa alone (P < 0.02). We conclude that: (a) hyperaminoacidemia specifically stimulates muscle protein synthesis; (b) insulin, even with hyperaminoacidemia, improves muscle protein balance solely by inhibiting proteolysis; and (c) hyperaminoacidemia combined with IGF-I enhances protein synthesis more than either alone.

Anti-vascular approaches to solid tumour therapy: evaluation of vinblastine and flavone acetic acid

Several agents have now been identified which exert their anti-tumour effects in large part via the tumour vasculature; these include TNF alpha and flavone acetic acid (FAA). More recently, Vincristine and Vinblastine have also been shown to cause a prolonged and selective decrease in tumour perfusion. Vinblastine, unlike, FAA, causes no increase in plasma TNF alpha levels in mice bearing the CaNT tumour, suggesting 2 distinct mechanisms of anti-vascular activity for these structurally diverse agents. Since FAA and Vinblastine also show quite different normal tissue toxicities, which are separately dose-limiting, we have examined the strategy of combining these 2 agents. When Vinblastine preceded FAA by 24 hr or less, tumour growth delay was significantly enhanced without a concomitant increase in toxicity. The level of enhancement was not significantly reduced by a 5-fold decrease in Vinblastine dose, though any reduction in the dose of FAA caused a rapid reduction in treatment effectiveness. Investigation of the functional vasculature of treated tumours suggested that increased anti-vascular effects may contribute to the enhanced growth inhibition of the combined treatment. Our results demonstrate the potential benefit of combining 2 different classes of anti-vascular agent, using Vinblastine and FAA (or 5,6-MeXAA) as prototype drugs.

Mitochondrial pyruvate dehydrogenase. Molecular cloning of the E1 alpha subunit and expression analysis

A polymerase chain reaction-based approach was used to isolate cDNA clones encoding the E1 alpha subunit of the mitochondrial pyruvate dehydrogenase from higher plants. Putative full-length clones were identified on the basis of similarity to E1 alpha sequences from nonplant sources. Southern blot analysis revealed a small family of genes in potato (Solanum tuberosum L.), whereas in cucumber (Cucumis sativus) there are only one or two genes. Tissue-specific variation in the relative amounts of E1 alpha mRNA was observed in northern blot analysis of different potato tissues, with the highest steady-state transcript levels found in floral tissue. Measurement of pyruvate dehydrogenase activity in cucumber cotyledons showed that there is a transient increase to a maximum at 4 to 5 d postimbibition. Western blot analysis revealed that the amount of E1 alpha protein also peaks at this time. Steady-state transcript levels in germinating cucumber cotyledons also show transient accumulation, peaking 2 d postimbibition. These data are consistent with regulation of E1 alpha at the level of transcription and/or mRNA stability in postgerminative cucumber cotyledons.