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Biomedical subjects

M T Martin

Publications and source records attributed to M T Martin.

At least 37 records · Page 2Linked to original sources
PubMed1999

Pyrrolidinoindoline alkaloids from Psychotria oleoides and Psychotria lyciiflora.

The chemical study of two Rubiaceae from New Caledonia, Psychotria lyciiflora and Psychotria oleoides, led to the isolation of several pyrrolidinoindoline alkaloids. Two dimers, the known meso-chimonanthine (9) and the new Nb-desmethyl-meso-chimonanthine (5), and a known trimer, hodgkinsine (1), have been isolated from P. lyciiflora. Hodgkinsine (1), quadrigemine C (2), isopsychotridine B (3), psychotridine (4), and three new alkaloids, quadrigemine I (6), oleoidine (7), and caledonine (8), have been isolated from P. oleoides. Structural assignments of the compounds were based on mass spectra analysis and 2D NMR experiments. A tentative stereochemical determination is made from 2D NMR experiments, circular dichroism study and chemical correlations. Some of these compounds are functional antagonists of somatostatine (SRIH).

Alkaloids↗
PubMed1999

Cytotoxic 3,4-secoapotirucallanes from Aaglaia argentea bark.

Nine 3,4-secoapotirucallanes, argentinic acids A-I, were isolated from the bark of Aglaia argentea and transformed to their methyl esters 1-9. The structures were determined by spectral and chemical means. Compounds 1-8 showed moderate cytotoxic activity against KB cells (IC50 1.0-3.5 microg/mL).

Antineoplastic Agents, Phytogenic↗
PubMed1998

Stress responses of horses during a long period of transport in a commercial truck.

OBJECTIVES: To characterize progressive patterns of dehydration, stress responses, and water consumption in horses transported long distances in hot weather and to evaluate various measurements in detecting dehydration and stress in transported horses. DESIGN: Prospective study. ANIMALS: 30 mature, healthy horses. PROCEDURE: The following 4 treatment groups were studied: horses that were penned and offered water every 5 hours (n = 5), horses that were penned and not offered water (5), horses that were transported in a truck and offered water every 5 hours (10), and horses that were transported and not offered water (10). The study commenced after 6 hours of water deprivation. Every 4 hours, the truck returned to the pen area and body weights were measured, physical examinations were performed, and blood samples were obtained. During this 1-hour period, water was offered to some horses, depending on treatment group. RESULTS: After 24 hours of transport, 3 horses were judged unable to continue and the study was terminated. Horses that were penned and offered water drank a mean of 38.2 L and horses that were transported and offered water drank 20.9 L, but some of the latter horses did not drink until after 19 or 24 hours of transport. In horses that were transported or penned and not offered water, serum electrolyte concentrations were greater than reference range values by 19 hours. Most horses that were transported and offered water consumed adequate water to postpone severe dehydration beyond 24 hours. CLINICAL IMPLICATIONS: Tame horses in good condition and initially deprived of access of water for approximately 6 hours can be transported in groups in open trailers during hot, humid conditions for up to 24 hours before dehydration and fatigue become severe. Rectal temperature and appearance of the horses were the most useful measures for determining crisis situations.

Animals↗
PubMed1997

Argenteanones C-E and argenteanols B-E, cytotoxic cycloartanes from Aglaia argentea.

Seven new cycloartanes, argenteanones C-E (4-6) and argenteanols B-E (7-10), have been isolated from Aglaia argentea leaves. All of these compounds possess significant cytotoxic activity against KB cells (IC50 values between 3.7 and 6.2 micrograms/mL). Structure elucidation was performed by 2D NMR spectroscopy, aided by molecular modeling in the case of the side chain of compound 7.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Peyer's patches in murine AIDS: dissociation between lymphoproliferation and anergy.

RadLV-Rs infection induces a murine immunodeficiency syndrome associated with a dramatic enlargement of spleen and lymph nodes. Surprisingly, the lymphoproliferation excludes thymus and Peyer's patches (PP). To understand the cellular interactions underlying lymphoproliferation further, the authors investigated the fate of PP in RadLV-Rs infected mice. The atrophy of PP was mostly due to the depletion of B cells, while the proportion of CD4+ and CD8+ T cells was increased. Nevertheless, B cell phenotype was modified with the emergence of lymphocytes with a low expression of B220 in infected PP. T cells characterized by a memory/activated phenotype in control PP did not undergo phenotypical changes after viral infection (i.e. regarding Thy-1 and CD44 expression). Despite the absence of lymphoproliferation, PP T and B cells displayed altered responses to mitogens in vitro. Finally, alterations of the expression of adhesion molecules and vascular addressins could not explain the atrophy of PP by a reduced homing to this lymphoid site. B cells and T cells from normal PP are clearly different from lymph nodes (LN) lymphocytes. The authors propose that the particular functional state which characterizes PP lymphocytes influences the B cell/T cell crosstalk necessary for RadLV-Rs-induced lymphoproliferation.

Animals↗
PubMed1996

Attention deficits in depression: an electrophysiological marker.

EVENT-RELATED POTENTIALS were recorded in young depressed subjects and compared with results from controls. Subjects were required to respond to targets (rare high-frequency sounds) presented to a designated ear, and to ignore targets presented to the non-designated ear as well as standards (frequent low-frequency sounds) presented to either ear. The results confirm those previously obtained with elderly depressed patients, showing the same general profile of electrophysiological and behavioural differences, and in particular a substantial reduction of the N200 amplitude in response to attended targets in depressed subjects. It is suggested that the N200 component could be a marker of depression.

Adult↗
PubMed1996

Electrochemiluminescence-based detection of beta-lactam antibiotics and beta-lactamases.

Bacterial resistance to clinically administered beta-lactam antibiotics is usually caused by beta-lactamases, enzymes that hydrolytically inactivate the antibiotics. This paper describes the use of electrogenerated chemiluminescence (ECL) to detect beta-lactam antibiotics and their hydrolysis by beta-lactamases. All 10 tested antibiotics were detected on the basis of their ability to participate in an ECL reaction with ruthenium(II) tris(bipyridine). In every case, antibiotic-promoted ECL changed when the antibiotic was hydrolyzed by beta-lactamases or NaOH. Standard curves of antibiotic concentration versus ECL intensity showed that antibiotics could be quantitated to low micromolar concentrations. Substrate profiles were generated for four beta-lactamases using six structurally diverse beta-lactam antibiotics. ECL-based antibiotic detection was accomplished in untreated whole milk, and beta-lactamases were detected in crude bacterial broth culture. Because several structurally diverse antibiotics were detectable by ECL, this method may become valuable for the detection of many or all beta-lactam antibiotics and their inactivation by beta-lactamases.

Anti-Bacterial Agents↗
PubMed1996

Enzyme-triggered formation of electrochemiluminescent ruthenium complexes.

A sensitive enzyme assay is described using substrates derivatized with metal-binding ligands. Enzymes catalyzed changes in the abilities of substrates to bind to the nonelectrochemiluminescent complex ruthenium (II) bis(bipyridyl), Ru(bpy)2(2+), to form electrochemiluminescent mixed-ligand complexes. A highly electrochemiluminescent complex was formed between Ru(bpy)2(2+) and picolinic acid (1) but not picolinic acid ethyl ester (4), permitting the detection of 4 hydrolysis by pig liver esterase (PLE). Electrochemiluminescence (ECL) differences between Ru(bpy)2(2+) mixtures of 1 and 4 were detected to a lower concentration limit of 65pM. Under the conditions used in actual enzyme assays, it was possible to detect 4.4 pM PLE and the hydrolysis of 1.3 microM 4. In a second assay, leucine aminopeptidase (LAP) hydrolyzed 8-(L)-leucylaminoquinoline (9) to leucine and aminoquinoline (10). A mixed-ligand complex formed between (9) and Ru(bpy)2 (2+) was substantially more electrochemiluminescent than a complex of Ru(bpy)2(2+) and 10. ECL differences between Ru(bpy)2(2+) mixtures of 9 and 10 were detectable to 65 nM. Under actual enzyme assay conditions, 375 pM LAP could be detected as well as the hydrolysis of 1.3 microM 9.

2,2'-Dipyridyl↗
PubMed1996

Cytotoxic cycloartanes from Aglaia argentea.

Aglaia argentea leaves yielded three new cycloartanes: argenteanones A and B, and argenteanol. The first two possess cytotoxic activity against KB cells (IC50 7.5 micrograms ml-1 and 6.5 micrograms ml-1 respectively). Structural elucidation was done by two-dimensional NMR spectroscopy.

Cell Survival↗
PubMed1996

Chromosome 17 allelic loss and NF1-GRD mutations do not play a significant role as molecular mechanisms leading to melanoma tumorigenesis.

Allelic loss in human cutaneous melanoma has been detected on chromosomes 1p, 6q, 9p, 10q, and 11q. Chromosome 17 contains important tumor suppressor genes such as p53, NM23, and neurofibromatosis type 1 (NF1), which have been implicated in melanoma tumorigenesis. The role of p53 has already been studied by a number of laboratories, showing contrasting results. In the present study, two restriction fragment length polymorphism (RFLP) probes for the NM23 and NF1 genes, together with five other RFLP and four variable number of tandem repeat chromosome 17 probes, were investigated at the loss of heterozygosity (LOH) level in a Southern blot-based assay. The NF1 gene was also tested for LOH by a polymerase chain reaction (PCR)-based approach in two different experiments, using a dinucleotide repeat polymorphic probe at locus D17S250 (17q11.2-q12), and an Alu probe intragenic to the NF1 gene (17q11.2). A PCR single-strand conformation polymorphism assay was included in the study for mutation detection at the NF1-GTPase-activating protein-related domain (GRD). A total of 68 melanocytic tumors were analyzed. LOH was detected in 9 of 87 informative cases (10%). LEW301 (17p11.2-pcen) presented the highest LOH frequency (22%). NM23 showed LOH in 17% of the informative cases, while NF1 did not show either LOH in the Southern blot- and PCR-based experiments or mutations at the NF1-GRD. These results are in concordance with those of previous smaller studies, but when compared with higher LOH frequencies obtained from other chromosomes, these findings indicate that the LOH values found in our study can most likely be attributed to background effect. Thus, chromosome 17 LOH is likely to play and unimportant role as a genetic event in melanoma tumorigenesis. Nevertheless, NF1 merits further study, since homozygous deletions have been detected at this locus in melanoma cell lines.

Alleles↗
PubMed1995

Spectrophotometric quantitation of silver in X-ray film images and silver-stained electrophoresis gel bands.

This paper describes a novel spectrophotometric method for quantitating the silver in silver-stained electrophoresis gel bands and X-ray film images. Silver in excised areas is quantitated by (i) oxidation/solubilization of Ag0 to Ag+ with nitric acid, (ii) neutralization followed by extraction into an organic solution of dithizone (diphenylthiocarbazone), and (iii) visible absorbance measurement at 600 nm. Spectrophotometric quantitation is possible because dithizone undergoes a dramatic color change from blue-green to yellow upon binding Ag+ (delta epsilon 600 = 3.28 x 10(4) M-1 cm-1). Experiments with silver-stained gels and with X-ray film images obtained by chemiluminescence and autoradiography demonstrated that the color change relates to the amount of silver present and hence to the amount of material represented by the band or image. This method is a convenient, inexpensive alternative to the use of a densitometer to quantitate silver-containing images.

Electrophoresis, Polyacrylamide Gel↗
PubMed1995

Properties of the active plum pox potyvirus RNA polymerase complex in defined glycerol gradient fractions.

As a first step in the study of the replication of plum pox virus (PPV) RNA, an in vitro virus-specific RNA polymerase activity was characterized in a crude membrane extract (Martin and Garcia, 1991). In this study, we report the fractionation of the crude membrane extract by centrifugation in glycerol gradients. The sedimentation properties after different treatments of the crude extract and its insensitivity to micrococcal nuclease treatment suggest that the RNA polymerase activity was localized in a defined and enclosed membranous structure. Subcellular membrane characterization of the different glycerol gradient fractions indicated that PPV-specific RNA synthesis occurred in fractions enriched in endoplasmic reticulum and tonoplast vesicles.

Centrifugation, Density Gradient↗
PubMed1994

Analysis by in situ hybridization of cytokine mRNA expression in the murine developing thymus.

We have used in situ hybridization to investigate the expression of IL-1, IL-2, IL-4, IL-6 and IFN-gamma genes by thymic cells during fetal development in mice. Two waves of mRNAs were detected in thymic cells for IL-1 at days 16 and 19 of gestation, for IL-2 at days 14 and 18, and for IL-4 at days 14 and 16. Three peaks for IL-6 were observed at days 13, 17 and around birth. Finally, only one peak of cells positive for IFN-gamma was detected. Whereas cells positive for IL-1 were generally grouped and more often localized in the external area of the thymus, the other positive cells were isolated and evenly distributed in the thymus. Our results illustrated the presence of cytokine transcripts in the developing thymus following a developmentally controlled sequence and support the hypothesis that cytokines could play a role in T cell development.

Animals↗
PubMed1994

Population dynamics of CD4+ T cells lacking Thy-1 in murine retrovirus-induced immunodeficiency syndrome (MAIDS).

Increased numbers of CD4+ Thy-1- cells have been described in the spleen (SP) of mice with retrovirus-induced immunodeficiency (MAIDS). Since this phenotypic abnormality might have considerable functional importance, the expansion of the CD4+ Thy-1- subset in MAIDS was characterized further. CD4+ Thy-1- and Thy-1+ T-cells from infected mice expressed similar densities of CD3 and TCR alpha/beta. In contrast, the Thy-1- subset was uniformly CD44hi, even early in the disease when part of Thy-1+ cells were still CD44lo. The emergence of CD4+ Thy-1- cells occurred first in SP and lymph nodes and was observed later in thymus. The important fraction of CD4+ cells lacking Thy-1 normally present in Peyer's patches was only weakly modified. Despite the major expansion of the CD4+ Thy-1- phenotype, the proliferating fraction was not higher in this subset than in CD4+ Thy-1+ cells from infected mice. Persistence after hydroxyurea administration was identical in both subsets, indicating similar mean cell lifespans. Taken together, these results show that the major expansion of CD4+ Thy-1- T-cells in MAIDS is not ascribable solely to increased proliferation within this subset. Phenotypic analysis suggests that CD4+ Thy-1- cells result from the differentiation of Thy-1+ cells induced by activation signals related to retroviral infection.

Animals↗
PubMed1994

p53 expression in cutaneous malignant melanoma: an immunohistochemical study of 87 cases of primary, recurrent, and metastatic melanoma.

Recent studies on the role of the p53 gene in human melanoma have largely been contradictory. To further assess p53 expression in melanoma, we have studied p53 immunoreactivity in 87 cases of primary, recurrent, and metastatic melanoma. Routine immunostaining was performed on paraffin sections with the monoclonal antibody PAb1801 and a streptavidin-biotin method. All specimens were blindly and independently assessed by two observers for number of melanoma cells with granular nuclear staining. Seven melanomas (8%) exhibited from 1 to 50% positive cells and another eight cases (9%) showed p53 immunoreactivity in < 1% of cells. All of the melanomas found to be positive for p53 with one exception (< 1.50 mm) were either thicker than 1.50 mm, recurrent, or metastatic. We conclude that these findings provide little evidence for significant p53 alteration in the initiation and development of melanoma.

Humans↗
PubMed1993

Mechanism-based catalytic antibody inactivation.

Studies of alternative substrates of the catalytic monoclonal antibodies 18H4, 7D4, and 45A11 provided us with a better understanding of the mechanism of ester hydrolysis employed by these isoabzymes. The antibodies were studied with analogs of the substrate, phenyl acetate; N-acetylglycine phenyl ester 3 and N-carbobenzoxy-glycine phenyl ester 4. All three antibodies catalyzed 3 hydrolysis with kinetic constants similar to those seen with phenyl acetate hydrolysis. However, 4 was found to be a mechanism-based (suicide) inactivator of 18H4 with a kinact of 0.29 min-1 and a K' of 64 microM. Antibody 18H4 was inactivated by 4 after 3.6 turnovers resulting in the acylation of 1.6 tyrosines per combining site. The data conform to a mechanism in which an inactive O-ZGly-tyrosyl-antibody is formed via a Michaelis complex.

Antibodies, Monoclonal↗