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Biomedical subjects

R F Martin

Publications and source records attributed to R F Martin.

At least 73 records · Page 4Linked to original sources
PubMed1986

Mesencephalic trigeminal sensory neurons of cat: axon pathways and structure of mechanoreceptive endings in periodontal ligament.

We injected 3H-proline into cat brainstem in order to label the entire mesencephalic trigeminal nucleus (Mes-V) for autoradiographic analysis of the size and pathways of Mes-V sensory axons and for microscopic study of Mes-V receptor structure in dental tissue. Labeled sensory axons were found in the trigeminal motor and sensory tracts and roots; approximately equal numbers of axons were found in both roots. The sensory root and all three divisions of the trigeminal nerve contained larger Mes-V axons than the motor root. Labeled Mes-V axons were found at the ganglion in the dorsomedial (infratrochlear) branch of the ophthalmic nerve but not in the ventrolateral branch. The mean diameter of Mes-V axons in periodontal ligament was 4.0 +/- 1.9 micron compared to 7.3 +/- 2.1 micron in maxillary and mandibular nerve, suggesting axonal arborization prior to innervation of ligament. Mes-V receptors in dental tissue were confined to ipsilateral periodontal ligament close to the root apex, with greater innervation on the posterior side. Receptor incidence was moderate for most teeth; however, maxillary first and second incisors and maxillary and mandibular canines had focal areas with remarkably dense innervation. No labeled axons were found in pulp of any ipsilateral teeth, and none was found in any contralateral dental tissue. EM-autoradiography demonstrated that Mes-V axons form unencapsulated Ruffini-like mechanoreceptors in periodontal ligament. The preterminal axons were small and myelinated. Neighboring bundles of unmyelinated axons and rare encapsulated endings were not labeled. The labeled mechanoreceptors branched to varying degrees among the ligament fibers; they contained numerous mitochondria and glycogen particles, as well as some vesicles and rare multivesicular bodies. They were surrounded by special Schwann cells that formed one or several layers around the ending. The endings were exposed to the basal lamina at numerous sites and occasionally extended fingers beyond the lamellar Schwann cells to contact ligament collagen.

Animals↗
PubMed1985

The sequence specificity of bleomycin-induced DNA damage in intact cells.

Bleomycin causes lesions to DNA in intact cells and in purified DNA under appropriate conditions. Using a middle repetitive DNA sequence called alpha-DNA as a target sequence, we have compared the sequence specificity of bleomycin-induced DNA cleavage in intact human cells and in purified human DNA. Bleomycin induces numerous cleavage sites in alpha-DNA which vary widely in intensity and give rise to a complex pattern of bands on a DNA sequencing gel. Unexpectedly, the intensity and position of bleomycin-induced DNA cleavage sites are very similar in intact human cells and in purified human DNA.

Base Sequence↗
PubMed1985

Physiological properties of intradental mechanoreceptors.

A major role of tooth receptors in signaling overt or impending tissue damage (nociception) has been previously established by substantial evidence from mechanical, thermal and chemical stimulation of exposed dentin. We report evidence showing that some intradental receptors in canine teeth of the cat detect mechanical transients applied to intact enamel. This new finding suggests that dental innervation may play an important non-nociceptive role in oral function such as detecting tooth contact during mastication and swallowing.

Animals↗
PubMed1985

Comparison of the sequence specificity of bleomycin cleavage in two slightly different DNA sequences.

The sequence specificity of bleomycin damage was investigated utilising 340 bp alpha-DNA (a middle repetitive sequence in the human genome) as a target sequence. The following significant facts were found:- i) The dinucleotides GT and GC were cleaved on all occasions, GA most of the time, and AT, AC, GG and AA cleaved some of the time; ii) The base immediately 5' to the purine-pyrimidine dinucleotides was found to be statistically highly significant in determining the degree of damage caused by bleomycin, while other nearest neighbour bases had no significant effect; iii) The sequence specificity of bleomycin damage was determined on both strands and it was found that damage on either strand follows the above dinucleotide preference and is independent of the extent of damage on the opposite strand; iv) Bleomycin damage was compared between genomic 340 bp alpha-DNA and a cloned alpha-DNA with eleven base substitutions relative to the "consensus" sequence. There were forty-nine detectable differences in intensity of damage between these two DNA molecules. Although four of the differences can be directly attributed to changes in base sequence, the remaining differences were not at the base substitution sites. Some of the differences were over fifty base pairs from the nearest base substitution. We propose that the majority of these differences are due to microvariation in the structure of DNA with a slightly different DNA sequence.

Base Sequence↗
PubMed1985

DNA-binding compounds--synthesis and intercalating properties of a peptide-diamino diacridine.

A novel diacridine has been prepared in which two acridines are linked by a flexible peptide chain composed of gamma-aminobutyric acid, tyrosine, lysine and glycine. Synthesis of N-[9-acridinyl)-4-aminobutanoyl-tyrosyl-lysyl-lysyl-glycyl)-N'-(9- acridinyl)-1, 3-diaminopropane (VII) was achieved in 8% overall yield by a solution phase stepwise procedure. This compound binds to DNA by intercalation of both chromophores with at least a 140-fold enhancement of affinity compared to 9-aminoacridine.

Acridines↗
PubMed1985

Resolution of myositis ossificans in a hemophiliac.

Hemophilic myositis ossificans at the site of previous hemorrhage is a well recognised entity. A phenomenon, not previously described, is gradual absorption of a well corticated heterotopic bone over a period of five-and-a-half years. We here report this happening in a patient.

Child↗
PubMed1983

Midbrain nuclei projecting to the medial medulla oblongata in the monkey.

To identify the midbrain nuclei that project to the medial part of the lower brainstem in the monkey, labeled cells were mapped in the midbrain following the injection of horseradish peroxidase into the medial medulla oblongata. After the general distribution of labeled cells was observed in three animals with large injections, more discrete injections of HRP were made in different locations in six additional animals. The small injections were centered in the nucleus raphe magnus, nucleus reticularis gigantocellularis, or nucleus medullae oblongatae centralis. The five labeled midbrain nuclei were the periaqueductal gray, nucleus cuneiformis, deep layers of the superior colliculus, nucleus of Darkschewitsch, and the interstitial nucleus of Cajal. In addition, the parvocellular division of the red nucleus and the posterior pretectal nucleus contained large numbers of cells when the injection spread into the inferior olive. No major differences in the distribution of labeled cells between different injection sites were found with the exception that the superior colliculus did not contain any labeled cells when the injection was restricted to midline structures. The functional implications of these anatomical findings are discussed in relation to the descending control of pain.

Animals↗
PubMed1982

Cells of origin of the spinoreticular tract in the monkey.

The distribution of the cells of origin of the primate spinoreticular tract was determined following injections of horseradish peroxidase (HPR) into the pontomedullary reticular formation in Macaca fascicularis. Five animals received large bilateral injections which included the raphe nuclei and seven monkeys received smaller, unilateral injections. Sections sampled were from upper cervical levels, the cervical enlargement, upper and lower thoracic levels, and lumbosacral levels. The laminar distribution of spinoreticular cells in all spinal cord levels was comparable. More than half of the labeled cells were located ventromedially, in laminae VII and VIII. HRP-labeled cells were also found in the dorsal horn, primarily in the lateral reticulated part of lamina V. Some cells were also found in laminae I and X. Spinoreticular cells in the lumbosacral spinal cord mainly projected to the contralateral brainstem. In the cervical enlargement, however, a bilateral distribution of cells was observed following unilateral injections of HRP. Most spinoreticular cells were multipolar neurons with extensive dendritic ramifications. The distribution of spinoreticular cells is similar to the distribution of spinal cord neurons that project to the medial thalamus, but different from that of spinal neurons projecting to the ventrobasal complex. The anatomical organization of the spinoreticular tract is consistent with a role for this pathway in nociception.

Animals↗
PubMed1982

Effects of hydroxyurea on DNA synthesis in mouse L-cells.

The effect of the anti-metabolite hydroxyurea on DNA synthesis in mouse L-cells has been examined. It was shown previously that when DNA synthesis was diminished to very low levels by treatment with the drug there was preferential incorporation of added [3H]dThd into low molecular weight fragments (Martin, R.F., Radford, I. And Pardee, M. (1977) Biochem. Biophys. Res. Commun. 74, 9-15). On the basis of several criteria it is concluded here that these fragments are a product of semi-conservative nuclear DNA replication. The preferential labelling of DNA fragments, but not their size, is shown to be dependent on the hydroxyurea concentration used. These DNA fragments are also shown, by comparison with normal DNA replication intermediates, to comprise a heterogeneous population of 'larger-than-normal' fragments. Different models to account for these findings are considered and it is concluded that the results are compatible with a loss of coordination of DNA synthesis following drug treatment.

Animals↗
PubMed1982

Inhibition of DNA synthesis and cell death.

The association between DNA synthesis inhibition and cell death in mouse L-cells was investigated using the drug hydroxyurea. This drug produces a preferential labelling of low molecular weight DNA and dose-response studies revealed a correlation between this effect and cytoxicity. Investigation of the reassociation kinetics of DNA labelled during hydroxyurea inhibition showed an over-replication of middle repetitive sequences, but the concentration dependence of this effect was quite different to that of cytotoxicity.

Animals↗
PubMed1981

Range of radiochemical damage to DNA with decay of iodine-125.

Studies of the length of DNA fragments produced upon decay of iodine-125-labeled deoxycytidine that was located at a single position within a DNA fragment of defined sequence demonstrate that most radiochemical damage occurs within 15 to 20 angstroms of the site of iodine-125 decay. However, DNA strand breakage was detectable up to 70 angstroms from the site of iodine-125 decay.

Base Sequence↗
PubMed1981

Myositis ossificans in hemophilia.

A review of the radiographs of 60 hemophilia patients showed nine (15%) with ectopic new bone formation. Three of these patients had multiple sites of involvement. The high frequency discovered in this series contrasts with the paucity of descriptions to be found in the literature. This process of myositis ossificans affects the lower half of the body and probably represents dysplastic metaplasia developing at the site of an intramuscular hematoma when remote from bone, as well as ossification of hemorrhagic lesions related to the periosteum. In conventional radiographs anatomic localization of bone foci is difficult, but use of computed tomography permits precise identification of the affected muscle. There is negligible disability associated with this condition.

Adolescent↗
PubMed1981

Alteration of coagulation and selected clinical chemistry parameters in patients undergoing open heart surgery without transfusions.

Alteration of coagulation status and certain clinical chemistry laboratory determinations of 75 adult patients undergoing cardiopulmonary bypass procedures for acquired heart disease was studied during and after surgery. None of the patients was given transfusions of blood or blood components. With hemodilution, the mean hematocrit value dropped from 38% to 28% during the procedure. Fibrin degradation products and euglobulin lysis time were transiently abnormal. Factor V diminished somewhat during the procedure, whereas factors VIII and IX increased after surgery. Clottable fibrinogen values decreased slightly, but increased to an abnormally high value at 24 and 48 hours. Mean value of platelet counts decreased from 194,000 to 144,000/microliter immediately after surgery. Knowledge of expected deviation of coagulation factors and certain clinical chemistry tests following open heart surgery is helpful in evaluating the status of the postoperative patient.

Blood Coagulation↗
PubMed1981

Assays of serum aminoglycoside levels by BACTEC 460 in the presence of cefamandole and cefoxitin.

The effects of cefamandole and cefoxitin on the assays of serum containing gentamicin, tobramycin, or amikacin by the BACTEC 460 (Johnston Laboratories, Cockeysville, Md.) were studied. The results were analyzed to determine whether the presence of the test substances, cefamandole or cefoxitin, caused a statistically different mean value of aminoglycoside or increase in variance as compared with serum assayed in their absence. The results were then considered in light of medical significance to see whether the difference observed would have any real effect on patient care. The results of each analyses dictate that serum of patients treated with both amikacin and cefamandole be tested in triplicate.

Amikacin↗