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Biomedical subjects

L L Smith

Publications and source records attributed to L L Smith.

At least 145 records · Page 8Linked to original sources
PubMed1989

The accumulation of cystamine and its metabolism to taurine in rat lung slices.

The objective of these studies was to determine the accumulation and fate of the disulphide, cystamine by rat lung slices. Cystamine was accumulated by two active uptake systems that obeyed saturation kinetics, with apparent Km values of 12 and 503 microM, and maximal rates of 530 and 5900 nmol/g wet weight/hr respectively. The high affinity system was competitively inhibited by the diamine, putrescine and the herbicide paraquat, which are themselves accumulated. Thus, this pulmonary uptake process appears to be identical for all three compounds. In contrast, the low affinity process was not inhibited by putrescine, and this process results from the diffusion of cystamine into the cell and its subsequent metabolism. Upon accumulation, cystamine was metabolised, predominantly to the sulphonic acid, taurine, with 10-20% of the intracellular label covalently binding to protein. Conversion to taurine was unaffected by amine oxidase inhibitors, but was decreased after GSH depletion, suggesting that pulmonary cystamine metabolism is glutathione-dependent, and is not mediated by diamine oxidase. Both cystamine and taurine have been implicated as antioxidants, and we suggest that cystamine is actively accumulated by the lung as part of the process to protect pulmonary tissue against oxidative stress.

Animals↗
PubMed1989

Mutagenic lipid peroxides from edible oils.

Weak mutagenic activity was detected in several commercially available edible palm and corn oils using liquid incubation bioassays with Salmonella typhimurium TA1537. Chromatographic fractionation of unrefined palm oil established that mutagenic activity was present in three fractions that also contained fatty acyl hydroperoxides. Similar weak mutagenic activity was also demonstrated for linoleic and linolenic acid hydroperoxides. In all cases, the mutagenicity was abolished by exogenous catalase, implying that the observed activity was moderated by hydrogen peroxide.

Chromatography, High Pressure Liquid↗
PubMed1989

Hydrogen peroxide mutagenicity towards Salmonella typhimurium.

In bioassays conducted under controlled, comparable conditions, weak direct mutagenicity responses were observed for hydrogen peroxide in the standard (Ames test) agar plate incorporation bioassay with Salmonella typhimurium strains TA97, TA98, TA102, and TA1537, in a 20 min preincubation test with strains TA97, TA98, TA100, TA102, TA1537, and TA1538, and in a liquid incubation modification using strain TA1537. These results conclusively demonstrate that hydrogen peroxide is a weak mutagen, especially in strains that are sensitive to oxidative damage under suitable bioassay conditions.

Animals↗
PubMed1989

White blood cell response to uphill walking and downhill jogging at similar metabolic loads.

The object of this study was to determine whether leukocytosis would occur in response to eccentric exercise, to concentric exercise, and/or to possible increases in serum cortisol levels. Eight men performed 2 bouts of exercise at 46% VO2max for 40 min. Subjects initially walked up a 10% grade (UW); 2 weeks later they jogged down a 10% grade (DJ), a form of eccentric exercise known to induce delayed onset muscle soreness (DOMS). Venous blood samples were drawn before and after each exercise bout (0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, and 5 h). Total and differential WBCc and serum cortisol levels were assessed. Results were analyzed using repeated measures ANOVA (2 x 11). Subjects experienced severe DOMS after DJ. There was a significant difference in TWBCc (p less than 0.0001) between UW and DJ. Post-hoc testing revealed no significant increase over baseline values for UW; after DJ there was a 46% increase over baseline values (p less than 0.05) initially seen at 1.0 h. These increases in TWBCc were predominantly a reflection of increases in neutrophils which were significant (p less than 0.0001) when compared to baseline values at 1.0, 1.5 and 2.0 h (approximately 60%). No significant neutrophil increases were seen after UW. Cortisol levels were similar for both groups pre-exercise (UW = 367.1 +/- 38.6, DJ = 320.2 +/- 44.16 nmol.L-1 means +/- SE) and decreased similarly for both groups after exercise, and thus were not related to the post-exercise neutrophilia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Biological activities of oxysterols.

Literature dealing with the biological activities of cholesterol autoxidation products and related oxysterols in vivo and in vitro published since the previous 1981 monograph is reviewed. Although several oxysterols are important cholesterol metabolites implicated in bile acids and steroid hormones biosynthesis, effects on cellular membranes and on specific enzyme systems as well as cytotoxic, atherogenic, mutagenic, and carcinogenic activities characterize oxysterols as a class. Circumstantial evidence implicates oxysterols of the human diet and those formed in vivo with human health disorders, but recent work also supports an hypothesis that some oxysterols be endogenous intracellular regulators of de novo sterol biosynthesis. The true physiological relevance, if any, of these matters has not been adduced.

Animals↗
PubMed1989

Mechanistic studies: their role in the toxicological evaluation of pesticides.

To date, studies on the mechanism of toxicity of pesticides are not yet an integral part of the toxicological evaluation process. However, in recent years mechanistic studies have played an increasing role in the assessment of toxicological hazards to man, and in this paper we have described two examples where an understanding of mechanism has contributed positively to risk assessment or has provided a surer scientific basis for the judgement of whether a potential hazard will be expressed in man. In the first example, an evaluation of the scientific literature leads to the conclusion that hepatic peroxisome proliferation in rats and mice is directly, or indirectly, related to the development of hepatocellular tumours. A wide range of non-mutagenic chemicals elicit peroxisome proliferation in mouse and rat liver, but not the guinea pig or marmoset liver. Using one of the diphenyl ether herbicides, fomesafen, we have shown that isolated hepatocytes from mice and rats, but not those from guinea pigs, marmosets and significantly man, undergo peroxisome proliferation. Therefore, it seems reasonable to conclude that although fomesafen causes peroxisome-related tumours in the mouse, man is neither susceptible nor sensitive to this mechanism. Consequently, we can conclude that fomesafen will not cause liver tumours in humans exposed to this herbicide. The herbicide paraquat, although safe in normal agricultural use, has been responsible for numerous human fatalities, almost exclusively as a result of the intentional ingestion of the concentrated commercial product.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Competition for polyamine uptake into rat lung slices by WR2721 and analogues.

The objective of these studies was to determine whether a series of structurally related radioprotective agents could act as substrates for the recently identified polyamine system in the lung. We have shown that WR2721 (S-2(3-aminopropylamino)ethyl phosphorothioate), S-2(4-aminobutylamino)ethyl phosphorothioate (S-ABEP or WR2822) and S-2(7-aminoheptylamino)ethyl phosphorothioate (S-AHEP) competitively inhibit the uptake of putrescine into rat lung slices. The ability of the radioprotectors to act as substrates for the polyamine uptake system was expressed as the Ki for each compound. The Ki values for WR2721, S-ABEP and S-AHEP in the absence of dithiothreitol were 48, 57 and 7 mumol dm-3 compared to 155, 88 and 15 mumol dm-3 in the presence of dithiothreitol, indicating that the disulphide form may have a higher affinity for the transport system. By analogy with other substrates for the polyamine uptake system we have concluded that it should be possible to target radioprotectors to the alveolar epithelial type I and II cells and the Clara cells in the lung, as they prossess this uptake system, and thus protect these cells from oxidative stress.

Amifostine↗
PubMed1989

Inducible expression of encephalomyocarditis virus 3C protease activity in stably transformed mouse cell lines.

An inducible expression vector system has been developed to facilitate the study of the effects of individual virus gene products on cell function. The vector utilizes the mouse metallothionein promoter carried on the bovine papillomavirus genome. Conditions which optimize the induced expression of open reading frames inserted downstream from the mouse metallothionein promoter have recently been described. In this communication we describe the use of this system to clone and express the encephalomyocarditis virus 3C protease in cultured mouse cells. Stably transformed cell lines could be induced to produce levels of 3C protease activity comparable to those observed during normal virus infection. In spite of this, no effects on cellular protein synthesis rate or membrane permeability were observed. It was also discovered that 3C protease as well as 3C protease-containing polyproteins are turned over. This was true not only in the induced cell clones, but also during the normal course of encephalomyocarditis virus infection, as well as in translation systems in vitro. This phenomenon was highly specific for this family of polypeptides, perhaps explaining their apparent lack of cytotoxic effects.

3C Viral Proteases↗
PubMed1989

Medial brachial fascial compartment syndrome: anatomic basis of neuropathy after transaxillary arteriography.

The authors reviewed their experience with 320 transaxillary arteriograms, as well as the English-language literature on neuropathy complicating transaxillary arteriography. Three of their patients had median and ulnar motor and sensory nerve injury, and six others had only sensory involvement. The occurrence or severity of nerve injury did not correlate well with the size or presence of an observable axillary or arm hematoma. Dissection of the axillae and arms of 25 human cadavers revealed a tough medial brachial fascial compartment (MBFC) outside a thin axillary sheath. The median and ulnar nerves were within the MBFC at an arterial puncture site just lateral to the anterior axillary fold. The radial and musculocutaneous nerves exited the MBFC more proximally. The different levels at which the major nerves of the brachial plexus exit the MBFC explain the anatomic distribution of the nerve injuries associated with compression by a hematoma after transaxillary arteriography.

Adult↗
PubMed1988

Interferon-gamma and interleukin-1 alpha induce transient translocation of protein kinase C activity to membranes in a B lymphoid cell line. Evidence for a protein kinase C-independent pathway in lymphokine-induced cytoplasmic alkalinization.

We have previously shown that recombinant murine interferon-gamma, rIFN-gamma, and recombinant human interleukin-1 alpha, rIL-1 alpha, induce differentiation of murine pre-B-like cell line 70Z/3, a finding associated with stimulation of Na+/H+ exchange across the plasma membrane. The present study was designed to test whether the enhanced Na+/H+ exchange is mediated by Ca2+/phospholipid-dependent protein kinase C. The results show that two structurally different peptides, rIFN-gamma and rIL-1 alpha, induce identical patterns of transient translocation of protein kinase C from the cytosol to the membranes. The increase in membrane-associated protein kinase C activity was first detected 20 min after exposure to the lymphokines. This activity peaked at 30 min and was back to baseline by 2 h. At each time point, the increase in membrane-associated protein kinase C activity corresponded to a decrease in the activity of protein kinase C in the cytoplasmic fraction. The total cellular activity (cytosol + membrane) remained the same. Two series of experiments were carried out to test the role of protein kinase C in mediating the lymphokine-stimulated Na+/H+ exchange. In the first, the effects of rIFN-gamma and rIL-1 alpha on cytoplasmic pH were measured in the presence of a protein kinase C inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine, H-7. In the second, rIFN-gamma- and rIL-1 alpha-induced cytoplasmic alkalinization was determined in cells containing decreased protein kinase C activity. Under both experimental conditions, lymphokine-induced cytoplasmic alkalinization was not attenuated. These results indicate that, although both rIFN-gamma and rIL-1 alpha cause association of protein kinase C with membranes, activation of protein kinase C is not required for rIFN-gamma or rIL-1 alpha to stimulate Na+/H+ exchange across the plasma membrane.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1988

Recombinant murine interferon-gamma-induced differentiation of pre-B lymphocytes is associated with Na+/H+ exchange-dependent and -independent cytoplasmic alkalinization.

We have previously shown that in a murine pre-B lymphocyte cell line, 70Z/3, interleukin-1-induced IgM expression (differentiation) was associated with Na+/H+-mediated cytoplasmic alkalinization. Because interferon-gamma also induces 70Z/3 differentiation, in this study we examined the effects of recombinant murine interferon-gamma (rIFN-gamma) on cell pH. We found that rIFN-gamma (50 units/ml) induced a sustained increase in cell pH, averaging 0.09 pH units above the base line at 30 min and 0.08 at 4 h. Because rIFN-gamma also induced increases in cell Na+ concentration, the data suggests stimulation of Na+/H+ exchange across the cell membrane. Amiloride inhibited the rIFN-gamma-mediated pH rise by only 31% at 30 min, but at 4 h the inhibition was more complete (89%). In contrast to pHi, amiloride totally blocked the Na+ rise at both 30 min and 4 h. This indicates that at the earlier time point the pH rise had a Na+/H+ exchange-dependent and -independent component while at the later time most of the pH rise was due to the Na+/H+ exchanger. The presence of a Na+ independent amiloride-insensitive component was further confirmed by the 0.05 pH rise induced by rIFN-gamma in Na+-free media. Failure to block the Na+-independent rIFN-gamma-mediated pHi rise by anion exchange inhibitors or removal of Ca2+ indicate that this component was not mediated by Cl-/OH- or Ca2+/H+ exchange. The nature of the Na+-independent cell alkalinization process or its role in rIFN-gamma-mediated 70Z/3 differentiation remains to be determined. Because amiloride did not have an effect on rIFN-gamma-induced surface Ig expression or the rIFN-gamma-mediated increase in new kappa light chain-specific mRNA the results indicate that rIFN-gamma-stimulated Na+/H+ is not required for 70Z/3 differentiation.

Animals↗
PubMed1988

The accumulation and localisation of putrescine, spermidine, spermine and paraquat in the rat lung. In vitro and in vivo studies.

Putrescine was accumulated into the isolated perfused rat lung by a temperature dependent process. The uptake obeyed saturation kinetics for which an apparent Km of 14 microM and Vmax of 48 nmol/g wet wt/hr was derived. After rats were dosed subcutaneously with [14C]putrescine, it was accumulated in the lung to concentrations greater than that in the plasma with the highest amount found between 3 and 12 hr. From 3 hr after dosing until 24 hr, there was a progressive increase in 14C label incorporated into spermidine, indicating that putrescine was converted to spermidine. Using autoradiographic techniques in lung slices the [3H]oligoamines were found in the alveolar epithelial type II. Clara and very probably the alveolar type I cells. With [3H]paraquat, the presence was detected only in the alveolar type II cells. Likewise, in the isolated perfused rat lung or following s.c. dosing of rats with [3H]putrescine the radiolabel was located only in the alveolar type II cell. We have suggested that the most likely explanation for the differences in localisation of label between in vitro and in vivo studies resulted from the use of [3H] label of different specific activity. Consequently we have concluded that the cell types with the ability of accumulate paraquat and oligoamines were the alveolar epithelial type I and type II cells and Clara cells.

Animals↗
PubMed1988

Clinical implications of procoagulant and leukoattractant formation during intraoperative blood salvage.

Experiments using 21 dogs and red cell salvage equipment (Haemonetics Cell Saver, Haemonetics Corp, Braintree, Mass) were employed to study the formation and potency of procoagulant and leukoattractant material during experimental autologous blood salvage. Washed red cell suspensions were found to include toxic degradation products that had been released from a deposit of platelets and white cells adherent to the centrifuge bowl wall. When reinfused, these toxic products resulted in a "salvaged blood syndrome" of intravascular clotting and pulmonary damage. The pulmonary arterioles showed leukocyte margination and tangled fibrin skeins with occlusive thrombi. Intra-alveolar and perivascular hemorrhages, along with extensive pulmonary edema, were also observed. The formation of procoagulant and leukoattractant material could be markedly decreased when the red cell salvage technique incorporated the following precautions: (1) minimal dilution with saline (normal plasma protein levels), (2) a low calcium level, and (3) minimal platelet activation (avoidance of the aspiration of clotted blood just before processing).

Animals↗
PubMed1988

Pulmonary indoleamine 2,3-dioxygenase activity and its significance in the response of rats, mice, and rabbits to oxidative stress.

The physiological significance of the enzyme indoleamine 2,3,-dioxygenase (IDO) (EC 1.13.11.17), which consumes superoxide anion (O2-), is not known. Since this enzyme is found in high concentrations in lung tissue, we examined the possibility that IDO may protect against chemically induced oxidative stress in the lung. The induction of IDO by bacterial lipopolysaccharide (LPS) was found to be 20-fold in the mouse and 4-fold in the rat, but did not confer protection against paraquat-induced pulmonary toxicity. Moreover, paraquat, when dosed to rats or mice, did not induce pulmonary IDO activity. An elevation in the intracellular O2- concentration was sought by incubating lung slices with 5 mM diethyldithiocarbamate (DDTC) (to inhibit SOD), paraquat (10(-4) M), or methylene blue (10(-4) M) or under an atmosphere of 100% oxygen. These attempts did not enhance the IDO activity in lung slices prepared from control or LPS-treated rats and mice. There was also no evidence that the uptake of an IDO substrate, tryptophan, was limiting for IDO activity in rat and mouse lung slices. We have concluded in the case of rats and mice that the pulmonary IDO activity, even following induction, is too low for O2- to be the rate-limiting factor. For this reason IDO cannot act as a protective enzyme by scavenging O2- in the lung of these species. However, in the rabbit, a species comparatively resistant to paraquat- and oxygen-induced lung damage, pulmonary IDO activity is 170 times that of rats or mice. IDO activity in rabbit lung slices was increased 4-fold by incubation with 5 mM DDTC and 10-fold by incubation with methylene blue (10(-4) M). However, paraquat (10(-4) M and oxygen (100% atmosphere) were able to enhance IDO activity (5-fold) only when SOD had previously been inhibited. We have concluded that in the rabbit lung IDO is able to scavenge O2- and therefore has the potential to act as a protective enzyme in this species.

Animals↗