Biomedical subjects

T E Martin

Publications and source records attributed to T E Martin.

At least 73 records · Page 4Linked to original sources

PubMed1990

The Ramstein airshow disaster.

In August 1988 an aircraft of the Italian aerobatic display team fell into the spectator enclosure at the Ramstein Airshow, causing over 500 casualties. The survivors were triaged, treated and evacuated from Ramstein within 96 minutes. The speed and efficiency of this evacuation was a result of prior planning, thorough training, medical reinforcement, co-operation with other agencies and the availability of an abundance of vehicles for both air and road evacuation. Not suprisingly, though, problems did occur, especially with communications, casualty identification and documentation.

Accidents, Aviation↗

PubMed1989

Loss of proliferative potential during terminal differentiation coincides with the decreased abundance of a subset of heterogeneous ribonuclear proteins.

The decrease in abundance of a subset of highly conserved basic nuclear proteins is established to correlate with the loss of proliferative potential in association with the process of terminal differentiation in murine mesenchymal stem cells and human keratinocytes. These proteins, designated P2Ps for proliferation potential proteins, have apparent molecular masses of 30-40 kD, are associated with the 30-40S substructures of nuclear hnRNP complexes, and are recognized by antibodies made against core proteins of hnRNP particles. They also share an epitope in common with heat shock protein-90 (hsp90) and are recognized by two mAbs against hsp90. Two-dimensional electrophoretic Western blots furthermore show that P2Ps make up a subset of hnRNP proteins. Cells that possess these proteins express the potential to proliferate whether or not they are traversing the cell cycle. These include rapidly growing cells, reversibly growth-arrested cells, and nonterminally differentiated cells. In contrast, cells that have irreversibly lost their proliferative potential, such as terminally differentiated cells, show a marked reduction in the abundance of P2Ps as determined by immunodetection on Western blots. A correlation, therefore, exists between the presence of this subset of nuclear proteins and the proliferative potential in two cell types. These results raise the possibility that as a subset of hnRNP proteins, P2Ps may mediate posttranscriptional control of the processing of specific RNAs required for cell proliferation.

Animals↗

PubMed1989

Infertility in a large Royal Air Force general practice.

The presentation and management of infertility was studied in a group of 56 couples from the catchment area of a large Royal Air Force general practice. They represented an overall prevalence of 36 per 1000 couples in the population. Thirty seven couples (66%) were trying for their first pregnancy and 19 (34%) has experienced a previous conception. Disorders of ovulation occurred in 29 women (52%) whereas disorders of sperm production or function occurred in 21 men (38%). Other causes were less common. Twelve couples (21%) had more than one diagnosed cause for their infertility, but 21 (37%) withdrew voluntarily or were posted back to the UK during the study period. Only 10 couples (18%) were referred to hospital for specialist investigations or treatment. A logical scheme for the GP management of infertile couples was used. This regime may have been partially or wholly responsible for the 14 pregnancies (25%) reported.

Adult↗

PubMed1989

Withdrawal sequelae to cannabis use.

A specific withdrawal syndrome resulting from the prolonged use of cannabis is presented. It is believed to be an underreported set of symptoms that are now emerging in the United States as a result of the increasing potency of the drug and greater numbers of long-term users. Two case studies are presented which illustrate the cannabis withdrawal syndrome in an otherwise healthy 25-year-old male and an exacerbation of a preexisting affective disorder in a 38-year-old male who prior to his resumption of cannabis use was asymptomatic for 3 years with antidepressant medications. The cannabis withdrawal sequela is presented with a discussion of differential diagnosis and implications for treatment and future research.

Adult↗

PubMed1989

Ultrastructural distribution of ribonucleoprotein complexes during mitosis. snRNP antigens are contained in mitotic granule clusters.

The great majority of snRNP and hnRNP ribonucleoproteins have been shown to be confined to the nucleus except during periods of cell division. We have now determined the fine structure distribution of polypeptides associated with these RNP complexes during interphase and mitosis in mammalian tissue culture cells using immunoelectron microscopy. Many hnRNP antigens are found at the periphery of heterochromatin masses, known to be the sites of non-rRNP proteins initially surround areas of condensing chromatin and later become generally dispersed throughout the mitotic cell. The Sm protein antigens of snRNP complexes are found diffusely distributed in interphase nuclei as well as concentrated in fields of interchromatin granules (ICG). Proteins of snRNP complexes, unlike those of hnRNP, are associated with discernible cellular structures during mitosis. By prometaphase/metaphase, dense granular clusters are observed to contain a high concentration of snRNPs. These mitotic granule clusters (MGCs) are often in close proximity to chromosomal masses by late anaphase/telophase. The MGC structures are morphologically similar to interchromatin granule fields found in interphase nuclei. Furthermore, like interchromatin granules, they are sites of a high concentration of snRNP antigens and do not contain detectable hnRNP proteins or DNA.

Antigens↗

PubMed1988

Reversible chemical cross-linking and ribonuclease digestion analysis of the organization of proteins in ribonucleoprotein particles.

The organization of select proteins within ribonucleoprotein particles containing heterogeneous nuclear and uridine-rich small nuclear RNAs (hnRNP and UsnRNP respectively) was examined by chemical cross-linking and ribonuclease digestion using diagonal two dimensional PAGE and immunoblotting detection systems. Monoclonal antibodies specific for A2, C1 and C2 hnRNP proteins, detected these proteins at gel coordinates which suggested homotypic dimers and trimers of A2 and homotypic trimers, hexamers and larger multimers of C1 and C2. Ribonuclease digestion did not alter the cross-linking properties of hnRNP C1 and C2 proteins but did result in loss of A2 homotypic dimers and trimers. Blots simultaneously reacted with hnRNP specific monoclonal antibodies and autoimmune patient serum (RNP/Sm), or monoclonal antibodies reactive with the U1 snRNP specific 63 kDa protein and/or the UsnRNP common proteins B', B and D revealed no complexes which would indicate interactions between hnRNPs and UsnRNPs. The U1 UsnRNP specific 63 kDa protein appeared not to be cross-linked to UsnRNP common B', B and D proteins. The data also suggested that UsnRNP common protein D was cross-linkable to UsnRNP common proteins D', E and G but not to B' and B. The cross-linking properties of D were unaffected by ribonuclease digestion. In contrast, ribonuclease digestion resulted in an inability to cross-link select complexes containing either B' and B, or p63. The data suggest that both hnRNPs and UsnRNPs are comprised of RNA-dependent and RNA-independent protein-protein interactions.

Cross-Linking Reagents↗

PubMed1988

On the advantage of being different: Nest predation and the coexistence of bird species.

A long-standing debate in ecology centers on identifying the processes that determine which species coexist in a local community. Partitioning of resources, where species differ in resource use, is often thought to reflect the primary role of competition in determining coexistence of species. However, in theory predation can favor similar patterns. This theory premises that predators increase their search intensity with increasing density of prey. One set of experiments reported here supports this premise based on predators that search for bird nests. A second set of experiments documents that predation rates are lower when nest sites are partitioned among different sites than when the same number of nests are placed in similar sites. Moreover, predation rates on experimental nests are more similar to rates on real nests when experimental nests are partitioned among different sites. These results provide support for a hypothesis that nest predation is a process that can favor coexistence of bird species that partition resources, where nest sites are the resources.

Journal Article↗

PubMed1987

Redistribution of nuclear ribonucleoprotein antigens during herpes simplex virus infection.

Infection of human epidermoid carcinoma No. 2 cells with herpes simplex virus type 1 (HSV-1) leads to a reorganization of antigens associated with both the small and heterogeneous nuclear ribonucleoprotein complexes (snRNP and hnRNP). The hnRNP core protein antigens remain associated with the host chromatin, which appears to collapse into internal aggregates and along the nuclear envelope. More striking is the formation of prominent clusters of snRNP antigens (both general and U1 snRNP specific), which appear to condense throughout the nucleus then migrate to the periphery. These snRNP clusters have been identified at the fine structure level by immuno-electron microscopy. The HSV-1 presumed transcriptional activator ICP4, DNA-binding protein ICP8, and two capsid proteins ICP5 and p40 are not detectably associated with the snRNP clusters. Similar reorganization of snRNP occurs with HSV-2 and upon infection of African green monkey VERO cells with HSV-1. We speculate that the snRNP clusters arise from an increase in size and density of the interchromatin granule region of the host cell as a result of the partial inactivation of snRNP and host pre-mRNA splicing.

Animals↗

PubMed1987

Changes in heterogeneous nuclear RNP core polypeptide complements during the cell cycle.

Mammalian heterogeneous nuclear RNP (hnRNP) subcomplexes are shown to be comprised of 14-17 basic A and B core group polypeptides (chrp) when subjected to two-dimensional immunoblot analysis. These proteins are normally confined to the nucleus but are distributed throughout the cell during mitosis. However, not all of the 17 protein spots are observed for all stages of the cell cycle. HeLa cell populations have been synchronized and the basic hnRNP core protein complement examined during S, G2, mitosis, and G1. During cell division several distinct chrp polypeptide species at 35 and 37 kD appear, while another of 37 kD and a chrp of 38 kD are diminished. These altered chrp complements are not due to any effects induced by thymidine treatment but appear to be physiological changes in the chrp polypeptide modification state. The new charge isomers found during mitosis are not the result of selective phosphorylation of the chrp polypeptides. However the nature of the modifications has yet to be determined. The mitosis-specific modified forms of the chrp polypeptides are found in the cytoplasmic fraction derived from mitotic cell populations. When this fraction is centrifuged upon sucrose density gradients the modified chrp polypeptides sediment from 30-200S in a distribution similar to that of hnRNP complexes isolated from the nuclei of randomly dividing cell populations. RNase digestion experiments indicate that the general substructure of the RNA/protein complexes in mitotic cell cytoplasm is similar to that of nuclear hnRNP isolated from unsynchronized cells or tissue.

Antibodies, Monoclonal↗

PubMed1986

Complementarity of sequences in low molecular weight RNAs to regions of messenger and ribosomal RNAs.

Total low molecular weight nuclear RNAs of mouse ascites cells have been labeled in vitro and used as probes to search for complementary sequences contained in nuclear or cytoplasmic RNA. From a subset of hybridizing lmw RNAs, two major species of 58,000 and 35,000 mol. wt. have been identified as mouse 5 and 5.8S ribosomal RNA. Mouse 5 and 5.8S rRNA hybridize not only to 18 and 28S rRNA, respectively, but also to nuclear and cytoplasmic poly(A+) RNA. Northern blot analysis and oligo-dT cellulose chromatography have confirmed the intermolecular base-pairing of these two small rRNA sequences to total poly(A+) RNA as well as to purified rabbit globin mRNA. 5 and 5.8S rRNA also hybridize with positive (coding) but not negative (noncoding) strands of viral RNA. Temperature melting experiments have demonstrated that their hybrid stability with mRNA sequences is comparable to that observed for the 5S:18S and 5.8S:28S hybrids. The functional significance of 5 and 5.8S rRNA base-pairing with mRNAs and larger rRNAs is unknown, but these interactions could play important coordinating roles in ribosome structure, subunit interaction, and mRNA binding during translation.

Animals↗

PubMed1986

A low-molecular-weight RNA from mouse ascites cells that hybridizes to both 18S rRNA and mRNA sequences.

A low-molecular-weight RNA species from mouse ascites cells has been selected and purified by its intermolecular RNA X RNA hybridization capabilities. This 4.5S RNA is able to base pair with poly(A)+ mRNA sequences and with 18S rRNA. Melting experiments have shown that the intermolecular hybrids formed with this complementary low-molecular-weight RNA are of comparable stability to other RNA X RNA interactions. Analysis has shown that this hybridizing RNA is 87 nucleotides long and has an unusual sequence structure. Located near the 3' terminus is an alternating pyrimidine dinucleotide region of UUCCUUCCUU. This region along with the 3'-adjacent nucleotides form a 14-nucleotide sequence that exhibits perfect complementarity with 18S rRNA. An additional region of 10 nucleotides at the 3' terminus is perfectly homologous to a similarly located sequence in 5.8S rRNA. An obvious RNA polymerase III binding site is not found internally in this low-molecular-weight RNA sequence. The complementary and homologous character of hybridizing RNA with respect to rRNA and mRNA sequences suggests a potential regulatory role for this RNA in the coupling of ribosome and mRNA functions.

Animals↗

PubMed1986

Immunoelectron microscope visualization of nuclear ribonucleoprotein antigens within spread transcription complexes.

The ultrastructural distribution of nuclear ribonucleoproteins (RNP) within spread active chromatin has been investigated using specific anti-RNP antibodies. Monoclonal antibodies directed against the core proteins of heterogeneous nuclear (hn)RNP or against small nuclear (sn)RNP have been incubated directly with lysed mouse or Drosophila tissue culture cells and the bound antibodies visualized by means of a protein A-colloidal gold complex. The hnRNP core proteins have been localized on growing RNP fibrils within non-nucleolar transcription complexes. Anti-snRNP antibodies, directed either against the Sm-antigen (common for nucleoplasmic snRNP species containing U1, U2, U4, U5, and U6 RNAs) or against U1-snRNP, were bound by two morphological types of RNP structures. Within areas of chromatin that do not completely disperse, labeling was observed on RNP-fibril gradient type structures or on groups of fibrogranular material. In the well dispersed regions containing individual nonribosomal transcription complexes, snRNP antigens were associated with growing RNP fibrils. Our results provide direct evidence for association of some U-snRNP species (including U1-snRNP) with extranucleolar RNA as early as during transcription elongation. In addition, the presence of core hnRNP proteins on the same type of nascent RNA transcripts has been confirmed.

Animals↗

PubMed1985

Prevalence of Dirofilaria immitis and Dipetalonema reconditum in greyhounds.

Blood samples from 331 greyhounds in the Hunter Valley and nearby coastal areas of New South Wales were examined for microfilariae using a filtration technique. Species were identified by histochemical staining; 10.9% of the greyhounds were infected with Dirofilaria immitis and 3.6% with Dipetalonema reconditum. The prevalence of infection of both species was significantly greater in summer than in winter (p = less than 0.05). Infection with D. immitis was correlated with differences in age, sex, bodyweight and coat colour, and a reported lack of stamina and the presence of a cough. No significant association was found. Diethylcarbamazine citrate was used for prophylaxis in 8.8% of all the greyhounds examined.

Animals↗

PubMed1985

An evaluation of 4 commercially available ELISA kits for the diagnosis of Dirofilaria immitis infection in dogs.

Serum samples from 100 pound dogs were used to evaluate 4 commercial ELISA kits available for the diagnosis of Dirofilaria immitis. The kits were assessed on sensitivity (the ability to identify infected dogs), specificity (the ability to identify uninfected dogs) and accuracy (sensitivity plus specificity). The kits varied in sensitivity from 36% to 86%, in specificity from 44% to 70%, and in accuracy from 53% to 65%. The sensitivity was not affected by the age of the dogs, nor by the number of circulating microfilariae. The kits were most specific when testing the youngest dogs (less than = 3 years). The problems associated with the serological diagnosis of D. immitis infection in practice are discussed.

Animals↗

PubMed1984

Monoclonal antibodies to heterogeneous nuclear RNA-protein complexes. The core proteins comprise a conserved group of related polypeptides.

Hybridomas secreting monoclonal antibodies that react with heterogeneous nuclear ribonucleoprotein (hnRNP) core proteins have been isolated by immunizing BALB/c mice with RNP particles isolated from chicken and screening the fusion products with mouse RNP complexes. The antibodies show varying affinities for the hnRNP core proteins that have been blotted onto nitrocellulose. The majority of the immunoglobulins react with all the core group proteins although several recognize subsets of the hnRNP polypeptides. The clones are specific for different antigenic determinants as shown by their inability to compete with one another for binding sites. A mild proteolytic digestion of hnRNP proteins generates fragments that have uniformly lost 12 kDa and contain the antigenic determinants recognized by several of the monoclonal antibodies. Thus, it appears the core proteins comprise a family of related polypeptides possessing underlying structural similarities. Polypeptides similar in number and molecular weights that have antigenic determinants cross-reactive with those of mouse RNP have been found in a number of organisms, thereby emphasizing their possible common structure and function in higher eukaryotes. No difference in the distribution within the cell of individual or groups of core proteins has so far been detected by indirect immunofluorescence.

Animals↗

PubMed1984

Circulating androgen levels in the developing boar.

Circulating levels of serum androgens were studied for 11 Duroc boars. Jugular blood samples were collected at 2-wk intervals, beginning at 5 wk of age and continuing until 27 wk of age. Testosterone and androstenedione values were determined by radioimmunoassay. Analysis of variance indicated a significant difference among ages in testosterone and androstenedione concentrations. Plasma levels of testosterone were 1.5 to 1.9 ng/ml at 5 to 7 wk, decreased to 0.3 to 0.6 ng/ml between 7 and 17 wk, and then increased to 3.7 ng/ml by the 27th wk of age. Plasma androstenedione tended to be elevated during the 5th through 7th wk (3.5 to 4.9 ng/ml), decreased to 0.9 to 1.6 ng/ml through the 19th wk and then gradually increased through the 27th wk (1.4 to 2.4 ng/ml). A highly significant correlation was observed between testosterone and androstenedione (r=0.39). Testicular volume was shown to be highly correlated with testosterone concentration (r=0.48). During the early life of the pig, the predominant androgen is androstenedione with testosterone becoming the predominant androgen as the boar reaches maturity.

Journal Article↗

PubMed1984

Ultrastructural distribution of nuclear ribonucleoproteins as visualized by immunocytochemistry on thin sections.

The ultrastructural distribution of nuclear ribonucleoproteins (RNP) has been investigated by incubation of thin sections of mouse or rat liver, embedded in Lowicryl K4M or prepared by cryoultramicrotomy, with antibodies specific for RNP. The antibodies were localized by means of a protein A-colloidal gold complex. Anti-small nuclear (sn)RNP antibodies, specific for determinants of the nucleoplasmic snRNP species containing U1, U2, U4, U5, and U6 RNAs, were found associated preferentially with perichromatin fibrils, interchromatin granules, and coiled bodies. This indicates an early association of snRNP with structural constituents containing newly synthesized heterogeneous nuclear RNA. It also suggests a possible structural role of some snRNPs in nuclear architecture. Antibodies against the core proteins of heterogeneous nuclear RNP particles associate preferentially with the border regions of condensed chromatin, and in particular with perichromatin fibrils and some perichromatin granules. These results are discussed in view of recent knowledge about the possible role of nucleoplasmic RNP-containing components in the functions of the cell nucleus.

Animals↗

PubMed1983

Reconstitution of nucleoprotein complexes with mammalian heterogeneous nuclear ribonucleoprotein (hnRNP) core proteins.

Newly transcribed heterogeneous nuclear RNA (hnRNA) in the eucaryote cell nucleus is bound by proteins, giving rise to large ribonucleoprotein (RNP) fibrils with an inherent substructure consisting largely of relatively homogeneous approximately 20-nm 30S particles, which contain core polypeptides of 34,000-38,000 mol wt. To determine whether this group of proteins was sufficient for the assembly of the native beaded nucleoprotein structure, we dissociated 30S hnRNP purified from mouse ascites cells into their component proteins and RNA by treatment with the ionic detergent sodium deoxycholate and then reconstituted this complex by addition of Triton X-100 to sequester the deoxycholate. Dissociation and reassembly were assayed by sucrose gradient centrifugation, monitoring UV absorbance, protein composition, and radiolabeled nucleic acid, and by electron microscopy. Endogenous RNA was digested and reassembly of RNP complexes carried out with equivalent amounts of exogenous RNA or single-stranded DNA. These complexes are composed exclusively of groups of n 30S subunits, as determined by sucrose gradient and electron microscope analysis, where n is the length of the added nucleic acid divided by the length of nucleic acid bound by one native 30S complex (about 1,000 nucleotides). When the nucleic acid: protein stoichiometry in the reconstitution mixture was varied, only complexes composed of 30S subunits were formed; excess protein or nucleic acid remained unbound. These results strongly suggest that core proteins determine the basic structural properties of 30S subunits and hence of hnRNP. In vitro construction of RNP complexes using model nucleic acid molecules should prove useful to the further study of the processing of mRNA.

Animals↗