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Biomedical subjects

G R Martin

Publications and source records attributed to G R Martin.

At least 181 records · Page 10Linked to original sources
PubMed1990

Altered basement membrane protein biosynthesis by primary cultures of cpk/cpk mouse kidney.

Previously, kidneys from three-week-old cpk/cpk C57/B16 mice were found to contain elevated mRNA levels for the basement membrane components collagen IV and laminin [1]. Here primary cultures of kidney epithelial cells derived from cpk/cpk C57/B16 mice were established and the production of these proteins in culture was studied. Primary cultures of cpk/cpk mouse kidney epithelial cells were observed to have a more polygonal, flattened morphology than cells from unaffected littermate kidneys. The rate of collagen IV and laminin biosynthesis was determined by means of [35S] labelling studies followed by immunoprecipitation. Collagen IV and laminin biosynthesis are elevated by approximately twofold or more in primary cultures derived from 20-day-old cpk/cpk mice, as compared with parallel primary cultures derived from their unaffected littermates. Similarly, laminin B1 chain mRNA is elevated in primary cultures derived from 20-day-old cpk/cpk mice. In primary cultures derived from younger (day 11) mice, similar differences in the rates of both collagen and laminin biosynthesis were not observed between the two culture types. These observations are consistent with the previously reported age-dependent differences observed in laminin and in collagen IV gene expression in both cpk/cpk and wild-type mouse kidneys, and suggest that the regulation of overproduction of these proteins is due to an alteration in the kidney cells and not due to systemic factors.

Animals↗
PubMed1990

Reconstituted basement membrane (matrigel) and laminin can enhance the tumorigenicity and the drug resistance of small cell lung cancer cell lines.

Small cell lung cancer (SCLC) is a fatal malignancy due to its propensity to metastasize widely and to reoccur after chemotherapy in a drug-resistant form. While most SCLC cell lines are anchorage independent for growth, laminin induced the attachment of five of six SCLC cell lines tested (NCI-N417, NCI-H345, NCI-H146, NCI-H187, NCI-H510, and NCI-H209). NCI-N417 SCLC cells adopted a flattened morphology on laminin, and a classic SCLC cell line (NCI-H345) demonstrated a neuron-like appearance while the other SCLC cell lines except NCI-H187 cells, attached but did not spread. Adhesion to laminin was associated with increased resistance to several cytotoxic drugs. Matrigel, an extract of basement membrane proteins, greatly accelerated tumor growth when coinjected with SCLC cells in athymic mice. A synthetic peptide from the B1 chain of laminin, cyclic-YIGSR (Tyr-Ile-Gly-Ser-Arg), inhibited laminin-induced SCLC cell adhesion and migration in vitro and reduced the size of the tumors they formed when coinjected with matrigel and YIGSR. These results suggest that the interaction of SCLC cells with laminin and possibly with other basement membrane proteins can enhance their tumorigenicity and drug resistance.

Amino Acid Sequence↗
PubMed1990

Identification of an amino acid sequence from the laminin A chain that stimulates metastasis and collagenase IV production.

Tumor cells attach, degrade, and migrate through basement membranes as they metastasize. Laminin, a major glycoprotein of basement membranes, promotes the metastatic activity of tumor cells by stimulating the attachment and migration of the cells and their secretion of collagenase IV. We have identified a synthetic peptide of 19 amino acids (Cys-Ser-Arg-Ala-Arg-Lys-Gln-Ala-Ala-Ser-Ile-Lys-Val-Ala-Val-Ser-Ala-Asp -Arg) from the sequence of the A chain of laminin that increases experimental metastases of the lungs by murine melanoma cells. The peptide is active when injected either intravenously or intraperitoneally. The peptide increased collagenase IV activity, a key enzyme in the breakdown of basement membranes, to the same extent as laminin. This peptide represents an active site on laminin for promotion of the metastatic phenotype and generates a probe for studying the regulation of malignant activities.

Amino Acid Sequence↗
PubMed1990

5-Hydroxytryptamine receptor profile in healthy and diseased human epicardial coronary arteries.

STUDY OBJECTIVE: The aim of the study was to investigate the receptor events that mediate the vascular effects of 5-hydroxytryptamine (5-HT) on human coronary arteries, since 5-HT has long been thought to play a role in coronary artery vasospasm. DESIGN: Recently available selective receptor agonists and antagonists were used to examine the 5-HT receptor subtypes present in human epicardial coronary arteries using in vitro organ baths. EXPERIMENTAL MATERIAL: 138 segments of coronary arteries were obtained from 21 patients aged 2-66 years undergoing heart transplantation. MEASUREMENTS AND MAIN RESULTS: 5-HT produced only concentration dependent contractions of coronary artery segments. No evidence was obtained for 5-HT receptors mediating either endothelium dependent or endothelium independent vasorelaxation. In tissue from patients without ischaemic heart disease, 5-HT effects were mimicked by (+/-)-alpha-methyl-5-HT (alpha-me-5-HT), a selective agonist at 5-HT2 receptors. In addition, the selective 5-HT1-like receptor agonist GR43175 produced contractions which achieved 30% of the maximum response to 5-HT. Responses to alpha-me-5-HT were surmountably antagonised by the non-selective antagonist methiothepin (0.1 mumol.litre-1) as well as the 5-HT2 receptor antagonist ketanserin (0.1 mumol.litre-1). In contrast GR43175 effects were resistant to blockade by ketanserin, but remained sensitive to methiothepin. Responses to the two agonists were not antagonised by the 5-HT3 receptor antagonist MDL72222 (1.0 mumol.litre-1). Vessel segments from ischaemic heart disease patients also contracted to alpha-me-5-HT and GR43175. Diseased arteries contracted with a decrease in the maximal response induced by both alpha-me-5-HT and by 90 mM K+ depolarisation compared to "normal" vessels, but the effect of GR43175 was preserved in the diseased arteries. Vascular rings adjacent to an atheromatous lesion were more reactive to GR43175 than serial segments taken distal to the lesion. CONCLUSIONS: These results show that both 5-HT1-like and 5-HT2 receptors mediate contraction of human epicardial coronary arteries and indicate that effects mediated by 5-HT1-like receptors but not 5-HT2 receptors are preserved in patients with ischaemic heart disease.

Adolescent↗
PubMed1990

The role of basement membranes in vascular development.

Endothelial cells produce and bind to multiple basement membrane components. Fibronectin and interstitial collagens seem to promote migration and proliferation, whereas basement membrane collagen and laminin stimulate attachment and differentiation. Human umbilical vein endothelial cells will rapidly form capillary-like structures when plated on a reconstituted basement membrane gel. This morphological differentiation involves the alignment of the cells followed by their close association with one another and the formation of a central lumen. Using antibodies to basement membrane components, we find that the formation of these vessels is a complex process involving multiple interactions with several matrix components. Synthetic peptides to active sequences in laminin have demonstrated that at least two sites in laminin participate in tube formation. An RGD-containing site on the A chain appears to mediate cell to matrix adhesion, and synthetic RGD-containing peptides block cell to matrix adhesion during tube formation. A YIGSR-containing site on the B1 chain appears to mediate cell to cell adhesion and promote tube formation because synthetic peptides block the strong cell interactions involved in tube formation. Our data with laminin peptides show that for at least one protein, multiple sites are recognized. Such data would also suggest that several cellular receptors are involved in a concerted process in laminin-induced differentiation of endothelial cells. We conclude that vessel formation is a complex, multistep process. Identification of active sites that block this process may have potential use in blocking angiogenesis in diseases such as diabetic retinopathy and Kaposi's sarcoma.

Amino Acid Sequence↗
PubMed1990

Isolation of the mouse Hox-2.9 gene; analysis of embryonic expression suggests that positional information along the anterior-posterior axis is specified by mesoderm.

It is rapidly becoming accepted that the vertebrate neural tube, in particular the hindbrain, develops into a segmented structure. After segment formation, cells in the neural tube do not cross segmental boundaries, and segment-specific gene expression is observed. However, it is not known what positional cues instruct the neural tube to express genes in this restricted manner. We have cloned a murine homeobox-containing gene, Hox-2.9, whose expression in the neural tube at E9.5 is restricted to a segment of the hindbrain known as rhombomere 4. A study of its expression pattern earlier in development revealed that prior to the start of neurulation (E7.5) Hox-2.9 is expressed within a posterior to the embryonic mesoderm that will participate in hindbrain formation. With the onset of neurulation, expression then becomes detectable in the neural plate as well, but only in the part that overlies the Hox-2.9-expressing mesoderm; it is not detected in the more anterior neuroectoderm that will form the future midbrain and forebrain. On the basis of these findings, we propose that the mesoderm is providing cues that serve to instruct the overlying neuroectoderm with respect to its position along the anteroposterior axis and that Hox-2.9 participates in or reflects this process. As neurulation continues and individual segments form, a second phase of expression is detected in the neural tube in which high levels of Hox-2.9 transcripts become restricted to rhombomere 4. Hox-2.9 expression is also detected in the developing branchial arch units of the hindbrain region, in a pattern that suggests to us that here, too, mesoderm is providing a localized signal that induces Hox-2.9 expression, in this case in endoderm of the pharynx and in superficial ectoderm. In general, we interpret the expression patterns of Hox-2.9 in the hindbrain region as suggesting that the specific mechanisms of pattern formation in mammals are fundamentally similar to those of amphibians and avians - i.e. anteroposterior positional information is acquired by mesoderm, mesoderm induces positional values within (neuro-) ectoderm and endoderm, and both events occur within a restricted window of time.

Amino Acid Sequence↗
PubMed1989

A synthetic peptide containing the IKVAV sequence from the A chain of laminin mediates cell attachment, migration, and neurite outgrowth.

Laminin is a basement membrane glycoprotein which consists of A, B1, and B2 chains. Laminin has diverse biological activities including promoting cell adhesion, migration, differentiation, growth, and neurite extension. Synthetic peptides from the active region of the A chain were prepared and tested for their biological activity. A 19-mer peptide (designated PA22-2), from just above the carboxyl globule on the long arm of the A chain, was found to promote cell adhesion, spreading, migration, and neurite outgrowth. By testing smaller sequences within the 19-mer peptide, a constituent pentapeptide, IKVAV (Ile-Lys-Val-Ala-Val), was identified as the active site for cell adhesion and neurite outgrowth. These data suggest that this sequence is one of the principle sites in laminin which regulate cellular behavior.

Adrenal Gland Neoplasms↗
PubMed1989

Two different laminin domains mediate the differentiation of human endothelial cells into capillary-like structures in vitro.

Endothelial cells, both microvascular as well as large vessel, undergo differentiation slowly in culture under most conditions. When endothelial cells are cultured on Matrigel, a solid gel of basement membrane proteins, they rapidly align and form hollow tube-like structures. We show here that tube formation is a multi-step process induced by laminin. An RGD-containing sequence in the A chain of laminin through an integrin receptor on the endothelial cell induces their attachment to the protein while a YIGSR site in the B1 chain induces cell-cell interactions and the resulting tube formation. We also show that the laminin-derived synthetic peptide YIGSR contains sufficient information to induce single endothelial cells to form ring-like structures surrounding a hollow lumen, the basic putative unit in the formation of capillaries.

Capillaries↗
PubMed1989

Laminin A chain synthetic peptide which supports neurite outgrowth.

Neurons from peripheral and central nervous tissue as well as from established cell lines respond to low concentrations of laminin with rapid extension of axon-like processes. Two sites on laminin have been identified which stimulate neurite outgrowth, the major site residing at the end of the long arm of laminin. Recently laminin has been cloned and sequenced allowing for synthetic peptides to be prepared and tested for biological activity. We report here that antisera against synthetic peptides corresponding to A and to B1 chain sequences at the end of the long arm can partially inhibit laminin-mediated neurite outgrowth. Further, we show that a 19 amino acid synthetic peptide (CSRARKQAASIKVAVSADR) from the long arm of the laminin A chain is capable of stimulating neuronal-like process formation to almost the same extent as laminin and competes with laminin for stimulation of neurite outgrowth.

Adrenal Gland Neoplasms↗
PubMed1989

Identification of a cell surface-binding protein for the core protein of the basement membrane proteoglycan.

We have identified a protein(s) on the surface of hepatocytes that binds to the core protein of the heparan sulfate proteoglycan of basement membranes. These cells attached and spread on substrates prepared from the basement membrane heparan sulfate proteoglycan (HSPG) and its core protein (HSPG-core). Three proteins (Mr = 38,000, 36,000, and 26,000) were found to bind to a HSPG-core affinity column using extracts of iodinated hepatocytes, whereas proteins extracted from isolated membranes contained primarily the larger protein (Mr = 38,000). Similar results were obtained using a solid phase binding technique using labeled HSPG-core. Binding of HSPG-core to the protein (Mr = 38,000) was not altered by the presence of an excess of heparin, heparan sulfate, fibronectin, laminin, or collagen IV but was reduced by unlabeled HSPG-core. Similar studies showed that the binding protein (Mr = 3,0000) was present in extracts from the membranes of Engelbreth-Holm-Swarm tumor cells, Madin-Darby canine kidney cells, COS cells, melanoma cells, and rat kidney epithelial cells but not in fibroblasts. The protein was found in increased amounts in 3T3 cells treated with retinoic acid. These observations suggest that a variety of cells that contact basement membrane contain the proteoglycan-binding protein.

Animals↗
PubMed1989

Eicosapentaenoic acid reduces the invasive and metastatic activities of malignant tumor cells.

Recent studies have shown that the cyclooxygenase and the 5-lipoxygenase pathways of arachidonic acid, are required for the invasive and metastatic activity of certain tumor cells. We show here that malignant murine melanoma and human fibrosarcoma cells cultured in media supplemented with eicosapentaenoic acid show a dose and time dependent decrease in invasiveness, in collagenase IV production and in the case of the murine cells, a reduced ability to metastasize to the lung after intravenous injection. It was also shown that a metabolite of eicosapentaenoic acid was less potent than the comparable arachidonic acid metabolite in restoring collagenase IV production and invasiveness after inhibition of the lipoxygenase pathway. These studies indicate that such supplements have the potential to reduce the metastasis of certain tumor cells, converting them to benign status.

Animals↗
PubMed1989

Doppler echocardiographic evaluation of tilting-disc prosthetic heart valves in children.

To determine the Doppler characteristics of tilting-disc prosthetic heart valves in children, 22 children with mitral prostheses were studied 8 +/- 2 months after surgery, and 10 children with aortic prostheses were studied 37 +/- 26 months after surgery. All valves were thought to be functioning normally by clinical examination. Valve competence was interrogated and peak and mean velocities were measured by standard pulsed wave, continuous wave and color Doppler techniques. Prosthetic valve area was calculated and compared to the known valve area. Mild prosthetic valve regurgitation was present in 8 of 22 mitral and 7 of 10 aortic prostheses. For mitral prostheses, peak velocity was 192 +/- 41 cm/s, mean velocity was 118 +/- 37 cm/s and mean gradient was 7 +/- 4 mm Hg. For aortic prostheses, peak velocity was 287 +/- 88 cm/s, mean velocity was 197 +/- 59 cm/s, peak gradient was 36 +/- 21 mm Hg and mean gradient was 19 +/- 11 mm Hg. Prosthetic mitral valve area, calculated by the pressure half-time and modified Gorlin methods, correlated well with the known valve area (r = 0.89, standard error of the estimate = 0.29 and r = 0.95, standard error of the estimate = 0.21, respectively). Prosthetic aortic valve area, calculated by the modified Gorlin method, correlated well with the known valve area (r = 0.89, standard error of the estimate = 0.18). Residual valvular abnormalities are common after prosthetic valve insertion in children. Doppler estimates of prosthetic valve area correlate well with the known valve area but have a large standard error of the estimate.

Aortic Valve↗
PubMed1989

Influence of blood carbon dioxide pressure on growth index values in non-radiometric Bactec vials.

The influence of blood carbon dioxide pressure on growth index values yielded by the Bactec NR 660 system was evaluated. Growth index values of 1,175 Bactec blood culture vials collected from 293 patients were related to blood pCO2 and leukocyte concentrations. Thirty-three blood cultures were considered false-positive. These were significantly more frequently encountered in hypercapnia patients (5.4%) than in hypocapnia patients (1.7%) or normal patients (2.5%). There was no relationship between the growth index values and leukocyte concentrations.

Bacteria↗
PubMed1989

Identification of a second active site in laminin for promotion of cell adhesion and migration and inhibition of in vivo melanoma lung colonization.

Previously we reported that a pentapeptide (Tyr-Ile-Gly-Ser-Arg or YIGSR) from domain III of the B1 chain of laminin is a cell attachment site with the ability to stimulate cell adhesion and migration and to block experimental metastases. Here we report studies on the activities of synthetic peptides that cover domain III and report a second biologically active peptide PDSGR from this domain with activities similar to YIGSR. We also show that cyclic YIGSR is more potent in these assays than the linear peptide as expected since this sequence on laminin is bracketed by cysteines. Due to their proximity and similar spectrum of activities, it is possible that these sequences act in concert in the native laminin molecule.

Amino Acid Sequence↗
PubMed1989

Synteny on mouse chromosome 5 of homologs for human DNA loci linked to the Huntington disease gene.

Comparative mapping in man and mouse has revealed frequent conservation of chromosomal segments, offering a potential approach to human disease genes via their murine homologs. Using DNA markers near the Huntington disease gene on the short arm of chromosome 4, we defined a conserved linkage group on mouse chromosome 5. Linkage analyses using recombinant inbred strains, a standard outcross, and an interspecific backcross were used to assign homologs for five human loci, D4S43, D4S62, QDPR, D4S76, and D4S80, to chromosome 5 and to determine their relationships with previously mapped markers for this autosome. The relative order of the conserved loci was preserved in a linkage group that spanned 13% recombination in the interspecific backcross analysis. The most proximal of the conserved markers on the mouse map, D4S43h, showed no recombination with Emv-1, an endogenous ecotropic virus, in 84 outcross progeny and 19 recombinant inbred strains. Hx, a dominant mutation that causes deformities in limb development, maps approximately 2 cM proximal to Emv-1. Since the human D4S43 locus is less than 1 cM proximal to HD near the telomere of chromosome 4, the murine counterpart of the HD gene might lie between Hx and Emv-1 or D4S43h. Cloning of the region between these markers could generate new probes for conserved human sequences in the vicinity of the HD gene or possibly candidates for the murine counterpart of this human disease locus.

Animals↗