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Biomedical subjects

C M Lucas

Publications and source records attributed to C M Lucas.

At least 37 records · Page 2Linked to original sources
PubMed1991

Canine-specific adaptation of energy metabolism of latissimus dorsi muscle in response to chronic electrical stimulation.

Continuous electrical stimulation ot canine latissimus dorsi (LD) muscle in situ during 24 weeks induced an increase of immunohistochemically assayed type I fibers from about 30 to 80%. Concomitantly, the activity of fructose-6-phosphate kinase, a key enzyme of the glycolytic pathway, declined markedly, but the capacity for fatty acid oxidation remained unaltered. With respect to myofibrillar and metabolic properties the dog LD muscle initially resembled soleus muscle, and after 24 weeks of stimulation had acquired the properties of gastrocnemius muscle. It is concluded that in the dog, unlike the rat, the LD muscle has an inherently fixed capacity for oxidative energy production. Further expansion of its resistance to fatigue, as induced by chronic stimulation, most likely results mainly from a more efficient coupling between tension development and energy production.

Adaptation, Physiological↗
PubMed1991

The effect of L-carnitine on force development of the latissimus dorsi muscle in dogs.

Using the latissimus dorsi (LD) muscle of the dog in situ, the effect of carnitine was tested for increase of force in the first period after stimulation. Carnitine administration resulted in an increase of force of 31 +/- 6% (mean +/- SEM). It is hypothesized that, during muscle stimulation, a relative carnitine deficiency occurs in cells of the vascular compartment. The previously observed lesser effect of carnitine in the trained muscle than in the untrained muscle is in line with this hypothesis, since the number of capillaries is known to increase by training. Also in agreement with this hypothesis is the observation that carnitine increased flow during exercise of the muscle.

Animals↗
PubMed1991

Antibody response of humans to the circumsporozoite protein of Plasmodium vivax.

We studied the interaction of sera from residents of an area in northern Peru where vivax malaria is endemic with four recombinant DNA-derived circumsporozoite (CS) proteins of Plasmodium vivax. The antigens used in the enzyme-linked immunosorbent assay included one Escherichia coli-produced and three Saccharomyces cerevisiae-produced recombinant proteins. Three of the proteins (NS1(81)V20, Vivax-1, and Vivax-2) contain the entire central repeat region of the P. vivax CS protein, and one protein (Vivax-3) contains only two repeat sequences. Vivax-1, Vivax-2, and Vivax-3 contain different lengths of sequences flanking the repeats. A higher percentage of the sera had antibodies to Vivax-2 and Vivax-3, the two proteins containing the longest nonrepeat sequences, than to NS1(81)V20 or Vivax-1. Children less than 5 years of age did not have immunoglobulin G antibodies to NS1(81)V20; however, they had antibodies to Vivax-1, Vivax-2, and Vivax-3. The finding that individuals living in a malaria-endemic area produce antibodies to peptides containing nonrepeat regions of the CS protein emphasizes the need to characterize the immune response to these regions in naturally exposed and experimentally immunized humans.

Adolescent↗
PubMed1991

Acute effect of L-carnitine on skeletal muscle force tests in dogs.

Using the mixed type musculus latissimus dorsi of the dog in the present work, we show the effect of carnitine on an in situ fatigue test. L-Carnitine appears to improve force of this muscle by 34% while stimulated in situ. This effect of carnitine is acute and (stereo)specific, since neither D-carnitine nor the structural analogue choline (also a tertiary amine) has a positive effect on contractile force. Because skeletal muscle is rich in carnitine and because carnitine transport is slow, its effect must be exerted outside the striated muscle cells. Insulin (with glucose) administration abolished the carnitine effect. It is speculated that facilitation of fatty acid oxidation in the blood vessel wall is the basis for this positive effect of carnitine.

Blood Glucose↗
PubMed1990

Efficacy and toxicity of sodium stibogluconate for mucosal leishmaniasis.

OBJECTIVE: To determine the efficacy and toxicity of the World Health Organization's (WHO) recommended treatment for mucosal leishmaniasis: antimony, 20 mg/kg body weight per day for 28 days. DESIGN: Open trial with 12-month follow-up. SETTING: Inpatient unit of a regional referral hospital in a developing country. PATIENTS: Twenty-nine consecutive eligible patients with culture-confirmed infection of the mucosa with Leishmania species who were otherwise healthy. Eight patients (28%) had mild to moderate disease (confined to the nasal mucosa). Twenty-one patients (72%) had severe disease (including the oropharynx as well as the nasal mucosa). INTERVENTION: Antimony, 20 mg/kg body weight intravenously every day for 28 days. Patients received antimony in the form of sodium stibogluconate. MEASUREMENTS AND MAIN RESULTS: Initial results of therapy were as follows: 63 of 72 lesions (88%) healed or markedly improved; all lesions were culture-negative for parasites; and 18 of 29 patients (62%) showed complete clinical and parasitologic cure of all lesions. By the 12-month follow-up examinations, however, 37 lesions had recurred, 8 new lesions had appeared, and only 8 patients (30%) showed clinical cure of all lesions. Of the 8 patients with mild to moderate disease, 6 were cured compared with only 2 of the 21 patients with severe disease. Side effects of this treatment regimen included T-wave inversion on electrocardiogram (4 patients), abnormal liver function tests (10 patients), and musculoskeletal pain (24 patients). No side effects occurred during week 1 of therapy. CONCLUSIONS: The only recommended treatment for mucosal leishmaniasis is ineffective in patients with severe disease. The acceptable toxicity of the regimen suggests that longer courses of therapy with antimony, or that trials with other antileishmanial agents alone or combined with antimony be evaluated as initial therapy for this disease.

Adult↗
PubMed1990

Identification of a novel integrin beta subunit expressed on cultured monocytes (macrophages). Evidence that one alpha subunit can associate with multiple beta subunits.

The vitronectin receptor (VnR) is one member of a subset of cell adhesion receptors within the integrin supergene family which shares the beta 3 subunit (IIIa). We show here that the VnR is absent from the surface of monocytes freshly isolated from blood but is expressed on these cells after a period of in vitro culture. Such cultured monocytes (macrophages) from a patient with type I Glanzmann's thrombasthenia, however, failed to express the VnR. Instead, immunoprecipitation with a monoclonal antibody directed to the VnR alpha chain (alpha v) revealed a novel integrin comprising alpha v associated noncovalently with a 100-kDa beta subunit (beta 3b), immunologically unrelated to the VnR beta subunit (beta 3a). This same novel integrin complex was also identified on 10-day-old macrophages from healthy donors, but on these cells, the beta 3b subunit was co-expressed with the classical VnR complex of alpha v beta 3a. The novel beta 3b subunit was not identified by monoclonal or polyclonal antibodies to IIIa (beta 3a) nor by a monoclonal antibody to the classical VnR complex. The beta 3b subunit could be distinguished from beta 3a by its relatively greater migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis after reduction, by its distinct isoelectric point upon two-dimensional gel electrophoresis, and by one-dimensional peptide mapping. Neither platelets nor B lymphoblasts from this patient with Glanzmann's thrombasthenia expressed any VnR on their surface, whereas control cells from a normal donor expressed the classical VnR but not the beta 3b subunit. The two beta chains, and hence also the combined receptor complexes, appeared to be differentially regulated. These findings provide the first example of an integrin alpha chain complexed with more than a single beta chain in the same cell. Furthermore, the differential regulation of expression of the different beta subunits that associate with the VnR alpha chain on cultured monocytes suggests a role for the novel receptor complex during monocyte/macrophage differentiation.

Adult↗
PubMed1990

Blood leukocytes bind platelet glycoprotein (IIb-IIIa)' but do not express the vitronectin receptor.

Within the integrin family of Arg-Gly-Asp(RGD)-binding adhesion receptors, the subfamily defined by the beta chain known as beta-3 or glycoprotein (GP)IIIa is known to contain two individual receptors. These are the GPIIb-IIIa complex of platelets, where the alpha chain of the heterodimer is GPIIb, and the vitronectin receptor (VnR) containing the alpha V subunit. The presence of either GPIIb-IIIa and/or the VnR on blood leukocytes has been controversial. We have investigated this problem by performing immunoprecipitation and immunoblotting studies with rabbit and monoclonal antibodies (mAb) to each of the subunits of GPIIb-IIIa and the VnR. On cultured cells of different origin, it was established that almost all expressed the VnR but none had GPIIb-IIIa, and the only polypeptide associated with beta 3 was alpha V. Platelets expressed predominantly GPIIb-IIIa, and weakly, the VnR. Monocytes and neutrophils freshly isolated from blood did not express the VnR but bore on their surface a modified form of GPIIb-IIIa. This molecule appeared identical to GPIIb-IIIa but an epitope on GPIIb was masked on the intact cell and was only revealed after immunoblotting. We have termed this modified form of GPIIb-IIIa, GP(IIb-IIIa)'. With differentiation in culture, monocytes rapidly lost surface GP(IIb-IIIa)' and concurrently began to express the VnR. Evidence is presented that GP(IIb-IIIa)' is derived from particles released by activated platelets and is bound firmly to the leukocyte membrane. Its primary function does not seem to be to mediate attachment to matrix proteins; thus, although U937 cells bearing platelet-derived GP(IIb-IIIa)' bound fibrinogen in an RGD-dependent manner, isolated blood monocytes did not. It is suggested that this transfer of membrane proteins from platelets to monocytes and neutrophils may regulate the expression of the leukocyte VnR and also serve as a means of facilitating leukocyte procoagulant activity.

Amino Acid Sequence↗
PubMed1990

Diffuse cutaneous leishmaniasis acquired in Peru.

A case of diffuse cutaneous leishmaniasis (DCL) acquired in Peru is described. The causative agent was Leishmania mexicana amazonensis as determined by isoenzyme analysis and species-specific monoclonal antibody binding characteristics. Histological examination of biopsy material showed a large number of intracellular and extracellular amastigotes and few lymphocytes. Treatment with meglumine antimoniate (Glucantime) administered iv at a dosage of 20 mg antimony/kg body weight/day for 60 days resulted in visible improvement of the lesions, but not in clinical or parasitological cure.

Adult↗
PubMed1988

Synergism between membrane gangliosides and Arg-Gly-Asp-directed glycoprotein receptors in attachment to matrix proteins by melanoma cells.

The identification of specific cell surface glycoprotein receptors for Arg-Gly-Asp-containing extracellular matrix proteins such as fibronectin has focused attention on the role of gangliosides in this process. Is their involvement dependent or independent of the protein receptors? In attachment assays with cells from a human melanoma cell line, titration experiments with an antibody (Mel 3) with specificity for the disialogangliosides GD2 and GD3, used together with a synthetic peptide containing the cell binding sequence Arg-Gly-Asp, show that their joint effect is synergistic. Both the Mel 3 antibody and the synthetic peptide individually cause rapid detachment of melanoma cells from fibronectin substrate but, when used together, much smaller concentrations of both are required to achieve the same effect. The Mel 3 antibody was not nonspecifically reducing receptor binding to the Arg-Gly-Asp sequence since, in binding assays with radiolabeled peptide performed with cells in suspension, very little peptide is bound by the melanoma cells under these conditions but addition of Mel 3, an antibody of IgM isotype, causes a two- to threefold increase in specific binding. The simplest interpretation of these data is that the Mel 3 antibody is causing sufficient clustering of membrane gangliosides in local areas and producing a favorably charged environment to facilitate peptide binding by specific glycoprotein receptors.

Antibodies, Monoclonal↗
PubMed1988

Recombinant human granulocyte-macrophage colony-stimulating factor (rH GM-CSF) regulates f Met-Leu-Phe receptors on human neutrophils.

The regulation of mature human neutrophil function by recombinant human granulocyte-macrophage colony-stimulating factor (rH GM-CSF) was studied. Preincubation of neutrophils with this CSF did not stimulate superoxide anion directly but enhanced the subsequent release of superoxide anion in response to stimulation with the bacterial product formylmethionylleucyl-phenylalanine (f Met-Leu-Phe). Enhanced superoxide anion production was evident by 5 min and reached a plateau at 30 min. In contrast, neutrophils preincubated with rH GM-CSF exhibited reduced chemotaxis under agarose in response to a gradient of f Met-Leu-Phe. The inhibition of neutrophil migration was dependent on the dose of rH GM-CSF and exhibited a time-course similar to the effect on superoxide production. Binding studies of f Met-Leu-[3H]Phe to purified human neutrophils revealed heterogeneous binding to unstimulated cells. Two affinity components were identified. The high-affinity component consisted of approximately 2000 sites/cell and had an average Kd of 4 +/- 2 nM (n = 6). The low-affinity component consisted of approximately 40,000 sites/cell and had an average Kd of 220 +/- 130 nM (n = 6). rH GM-CSF caused conversion to a linear Scatchard plot showing no significant change in total binding sites but a single Kd of 30 +/- 10 nM. These data indicate that rH GM-CSF may influence neutrophil responses to f Met-Leu-Phe by regulating the affinity of f Met-Leu-Phe receptors.

Chemotaxis, Leukocyte↗
PubMed1987

Two distinct mechanisms for regulation of gamma-glutamyl transpeptidase in cultured rat hepatocytes by glucocorticoid-like steroids.

Adult rat hepatocytes maintained in primary monolayer culture with defined medium were used to characterise two effects of glucocorticoid-like steroids in regulating gamma-glutamyltranspeptidase (GGT). Low concentrations of glucocorticoids alone had little effect on GGT but synergistically enhanced induction of the enzyme by liver tumor-promoting xenobiotics such as 1,1,1-trichloro-2,2-bis-(4-chlorophenyl)-ethane (DDT) and hexachlorocyclohexane. The enhancing effect appears to be mediated by the classical glucocorticoid hormone receptor since structural requirements and concentration-dependence for enhancement were similar to those for induction of tyrosine aminotransferase in parallel cultures. Higher concentrations (1-100 microM) of various glucocorticoids alone increased GGT activity. Most glucocorticoids induced GGT but their order of potency did not parallel that for induction of tyrosine aminotransferase under similar culture conditions. Among the most potent glucocorticoids, triamcinolone was a weak GGT inducer and cortivazol appeared to act as an antagonist of GGT induction by steroids. Some non-glucocorticoids including pregnenolone 16 alpha-carbonitrile, and some progestins, also induced but required addition of 30 nM dexamethasone for maximal effect. Some specific steroid structural features were identified which increased (presence of a 16 alpha methyl group) or impaired GGT-inducing activity. Although interpretation is complicated by differential metabolism of individual steroids in culture, the results suggest that GGT induction by pharmacological levels of steroids may be mediated, directly or indirectly, by one or more relatively specific receptors distinct from the classical glucocorticoid receptor.

Animals↗
PubMed1987

Modulation of gamma-glutamyltranspeptidase in normal rat hepatocytes in culture by cell density, epidermal growth factor and agents which alter cell differentiation.

To help clarify whether elevation of gamma-glutamyltranspeptidase (GGT) in hepatocytes is associated with particular pattern(s) of liver differentiation, adult rat hepatocytes in primary culture were maintained for up to 5 days under conditions considered to alter differentiation in liver or other cells: basal GGT activity in untreated cultures and inducibility of the enzyme by known inducers such as dexamethasone, p,p'-dichlorodiphenyltrichloroethane or pregnenolone 16 alpha-carbonitrile were measured. Basal and induced GGT activities were maximal in confluent cultures and declined with decreasing cell density, an effect probably mediated by cell contact rather than factors in the culture medium. Opposite effects of cell density on GGT and DNA synthesis suggest that increased GGT activity is not linked with growth. Epidermal growth factor (EGF) increased basal GGT and augmented the action of xenobiotic inducers in lower density cultures, giving GGT activities approaching the levels in confluent cells. EGF had no effect on confluent cultures. Activators of protein kinase C such as tetradecanoyl phorbol acetate had significant but small inducing effects on GGT. Agents including all-trans retinoic acid, butyrate and dimethylsulfoxide which are considered to favour terminal differentiation in many cell types, all partly blocked induction of GGT by dexamethasone, EGF or xenobiotics. The results are consistent with (but do not prove) the view that elevated GGT activity may be associated with liver phenotype(s) distinct from terminal differentiation but not necessarily linked with growth.

Animals↗
PubMed1985

Phenobarbital and some other liver tumor promoters stimulate DNA synthesis in cultured rat hepatocytes.

Hepatocytes isolated from normal adult rats were maintained at sub-confluent density in a defined medium in primary culture. In control cultures with added epidermal growth factor and low concentrations of dexamethasone, the rate of DNA synthesis was initially low but increased after about 30 hours in culture. Addition of the xenobiotic liver tumor promoters phenobarbital, alpha-hexachlorocyclohexane or p,p'-dichlorodiphenyltrichloroethane to cultures after cell attachment caused concentration-dependent stimulation of DNA synthesis measured after 2 days in culture. While dexamethasone (30 nM) alone had little effect on hepatocyte DNA synthesis, the stimulatory effects of the xenobiotics required the permissive presence of the steroid.

Animals↗
PubMed1985

Induction of gamma-glutamyl transpeptidase in primary cultures of normal rat hepatocytes by liver tumor promoters and structurally related compounds.

Rat hepatocytes maintained for up to 6 days in primary culture were used to test a variety of xenobiotics and steroids for effects on the activity of gamma-glutamyltranspeptidase (GGT) in normal cells. In control cultures GGT activity was low and increased slowly with time. When added to cultures for 5 days, a variety of xenobiotics and steroids increased GGT activity to levels 2- to 6-times those of control cultures. Induction of GGT was potentiated for most test compounds by 20-30 nM dexamethasone and diminished by nicotinamide or adenosine-3',5'-monophosphate. Effective non-genotoxic inducers included phenobarbital and some structurally related compounds, p,p'-dichlorodiphenyltrichloroethane,alpha- and gamma-hexachlorocyclohexanes, Aroclor 1254, butyl hydroxytoluene, nafenopin, various estrogens, progesterone, pregnenolone-16 alpha-carbonitrile and cyproterone acetate. A number of compounds including barbituric acid, butyl hydroxyanisole, acetaminophen, saccharin, caffeine, clofibrate and some bile acids failed to induce GGT. Except for 2-acetylaminofluorene and diethylnitrosamine, genotoxic compounds tested did not increase GGT. The results establish that a structurally diverse group of xenobiotics and steroids, many of which are considered to be liver tumour promoters, may directly enhance GGT gene expression in normal hepatocytes. Thus, a variety of compounds used in experimental studies of liver cancer induction as promoters may elevate GGT by mechanism(s) not necessarily related to carcinogenesis.

Animals↗
PubMed1984

7-Ethoxycoumarin deethylase activity as a convenient measure of liver drug metabolizing enzymes: regulation in cultured rat hepatocytes.

Assays of 7-ethoxycoumarin O-deethylase (ECD) activity in intact cells were used as a sensitive and convenient measure of the drug-metabolizing activity of rat hepatocytes maintained for up to 4 days in primary culture. A combination of nicotinamide or other pyridines with dexamethasone was shown to maintain ECD at or above the activity of untreated livers in vivo and to potentiate induction by xenobiotics. Inductions in vivo and in culture were quantitatively similar but differed qualitatively as judged by the proportion of ECD activity inhibitable by metyrapone. A survey of possible endogenous regulators of liver monooxygenases established that: dexamethasone and other glucocorticoids induced ECD and potentiated induction by xenobiotics, particularly phenobarbitone; other steroids including testosterone, 17 beta-estradiol and pregnenolone 16 alpha-carbonitrile caused small inductions; insulin lowered both ECD activity and the proportion of activity inhibitable by metyrapone; dibutyryl cyclic AMP or glucagon lowered ECD; and high concentrations of aminolevulinate partly repressed induction by xenobiotics. Based on these findings, hepatocyte culture conditions which maintain ECD activity and inducibility at or above in vivo levels are defined.

7-Alkoxycoumarin O-Dealkylase↗