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Biomedical subjects

J H Martin

Publications and source records attributed to J H Martin.

At least 19 recordsLinked to original sources
PubMed1993

Differential spinal projections of subregions in the forelimb area of the motor cortex in the cat.

Anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was used to examine the topography of projections from the forelimb area of motor cortex to the cervical spinal cord in the cat. Tracer was injected in sites in the rostrolateral (RL-MCx) and caudolateral (CL-MCx) subregions concerned with the distal forelimb. Whereas both subregions projected throughout the cervical cord, with the greatest density of label present in the cervical enlargement, the dorso-ventral distributions were different for the two injection sites. Injections in RL-MCx produced labeling in the lateral portions of laminae VI, VII, and VIII in the upper cervical segments. This corresponds to the locations of propriospinal neurons that project to forelimb motor nuclei used in reaching [Exp. Brain Res., 42 (1981) 299-318]. In the cervical enlargement, labeling was present in laminae V, VI, VII, and part of VIII. At all levels examined, the density of labeling was greatest in the intermediate zone. After CL-MCx injection, labeling was concentrated in the dorsal horn both in the upper cervical segments and in the cervical enlargement. These findings suggest that the two motor cortical subregions project to different propriospinal and interneuronal systems in the cervical cord and support the idea that the two subregions play different roles in controlling forelimb movements.

Animals↗
PubMed1992

Susceptibility of corneas from various animal species to in vitro binding and invasion by Acanthamoeba castellanii [corrected].

A crucial requirement for establishing corneal infection by the extracellular protozoal parasite, Acanthamoeba, is the ability of the parasite to bind to the corneal surface. In a series of in vitro studies, we examined the ability of Acanthamoeba castellanii [corrected] to adhere, invade, and damage normal, intact corneas of 11 mammalian and one avian species. A. castellanii [corrected] (80-90% trophozoites and 10-20% cysts) were incubated with corneas for 24 hours in vitro and examined by scanning electron microscopy (SEM). Results of several independent SEM experiments revealed that parasites not only failed to produce cytopathic effects but did not even bind to the corneal epithelium of mice, rats, cotton rats, horses, guinea pigs, cows, chickens, dogs, and rabbits. However, parasites adhered, invaded, and produced severe damage to human, pig, and Chinese hamster corneas during the 24-hour in vitro incubation period. Additional in vitro experiments quantified the binding of A. castellanii [corrected] to the corneas of selected susceptible and nonsusceptible species. In vitro binding assays revealed scant binding of parasites to mouse, rat, and rabbit (range = 5-20 parasites/7.07 mm2 corneal button). In contrast, extensive binding was observed on Chinese hamster, pig, and human corneas (range = 100-200 parasites/7.07 mm2 button). The results indicate that A. castellanii [corrected] exercises rigid host specificity at the host cell surface.

Acanthamoeba↗
PubMed1991

Impairments in reaching during reversible inactivation of the distal forelimb representation of the motor cortex in the cat.

We report changes in the performance of a prehension task in the cat following focal inactivation of the rostrolateral subregion of the distal forelimb area of motor cortex (MCx) produced by muscimol microinjection. Animals reached into a cylindrical target to retrieve a morsel of food. Movements consisted of distinct lift and forward thrust phases following which the food was grasped and retrieved. In separate blocks of trials an obstacle was inserted in the path of the limb. Impact evoked an immediate compensatory trajectory change to bypass the obstruction and, on subsequent trials, an adaptive trajectory change to avoid impact. Inactivation produced three major defects: (1) uncompensated aiming biases to a location above the target; (2) loss of coordination of the grasp and food retrieval; and (3) impairment in trajectory adaptation to avoid impact of the limb with an obstacle. Thus, focal inactivation of the distal forelimb area of MCx produced disordered control of all forelimb joints. The impairment in trajectory adaptation and failure to compensate for aiming biases suggests that the MCx is important in motor learning.

Animals↗
PubMed1991

Autoradiographic estimation of the extent of reversible inactivation produced by microinjection of lidocaine and muscimol in the rat.

We used autoradiography to examine the extent of reversible inactivation produced by microinjection of lidocaine (40 micrograms/microliters saline) and muscimol (1 microgram/microliter saline). We measured intracortical spread of tracer amounts of labelled drug and local changes in uptake of [1-14C]glucose produced by the microinjection. The maximal average radii of regions of drug spread were 1.7 mm for both [14C]lidocaine and [3H]muscimol and were achieved within the first 20 min postinjection. The width of lidocaine injections decreased at longer postinjection times (30-60 min) but the width of muscimol injections remained relatively constant (30-120 min). Lidocaine radioactivity decreased faster from the injection site than muscimol radioactivity. Glucose autoradiograms showed a discrete region of maximally reduced glucose uptake (1.4 mm for lidocaine and 1.0 mm for muscimol) surrounded by a region of less reduced glucose uptake (up to approximately 3 mm). These findings suggest that, in the cortex, the effects of focal inactivation extend beyond the region of drug spread. Diffuse effects may be mediated of disfacilitation of cortico-cortical circuits.

Animals↗
PubMed1991

Cryofixation, ultracryomicrotomy, and X-ray microanalysis of enterocytes from chick duodenum: vitamin-D-induced formation of an apical tubulovesicular system.

New methods of tissue preparation were developed to study the morphology and distribution of calcium ions in duodenal enterocytes from normal, rachitic, and vitamin D-replete (either cholecalciferol [CC] or 1,25-dihydroxycholecalciferol [1,25-DHCC] treated) chicks. Frozen hydrated sections were prepared from cryofixed tissues by ultracryomicrotomy at -125 degrees C. Sections were subsequently freeze-dried by increasing the temperature to -100 degrees C. The latter temperature was maintained throughout both the structural and elemental analyses. In cells from normal, rachitic, and vitamin D-treated [CC] animals the brush border from lanthanum-infused tissues was electron dense and calcium-lanthanum positive by x-ray analysis. In the absence of lanthanum, i.e., sucrose-infused duodena, the microvilli were still calcium positive. In the terminal web region of normal and CC-treated enterocytes, numerous, apparently interconnected, tubules and vesicles were seen. Vacuole-like structures were also seen. Such structures were especially prominent in the enterocytes from the vitamin-treated [CC] animals. Except for the vacuoles, the tubules and vesicles were electron dense in the lanthanum-infused duodena, and clear in sucrose-infused tissues. In both instances, the structures were calcium positive. Similar, but even larger structures were seen below the terminal web. Here however, the tubules and vesicles seemed to be organized into multiple complex interconnecting networks, i.e., tubulo-vesicular complexes. Both the tubules and the vesicles seemed to be interconnected via smaller channel-like entities. The extensiveness of this structure was better appreciated in the enterocytes from lanthanum-infused tissues, where it appeared similar in structure and complexity to an en face view of the sarcoplasmic reticulum of skeletal muscle. These intestinal complexes were less well developed, decreased in number, and quite often absent, in the apical cytoplasm of absorptive cells from rachitic chicks. In the enterocytes from animals treated for 24 hours with 1,25-DHCC, the same highly developed tubulo-vesicular networks were again seen in the enterocyte apical cytoplasm. They were even more developed in the 1,25-DHCC-treated animals. All structures were intensely calcium positive in enterocytes from both the lanthanum- and the sucrose-infused preparations. Numerous endocytotic (pinocytotic) vesicles were seen at the lumenal plasmalemma. Similar structures were also apparent in the terminal web region of the 1,25-DHCC-treated enterocytes. Exocytotic vesicles were seen at the apical aspect of the lateral cell membrane, below the level of the junctional complex. All components of this unique system contained high concentrations of calcium.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Task-related coding of stimulus and response in cat red nucleus.

In the present study we recorded the activity of single neurons in the forelimb area of red nucleus (RN) during performance of three step-tracking tasks designed to dissociate the coding of stimulus and response variables in the discharge of recorded neurons. In two of these tasks, the standard and stimulus-reversal arm tasks, elbow flexion and extension were elicited by different stimuli enabling us to distinguish activity correlated with the forelimb response from the stimulus eliciting it. The third task (neck task) allowed us to determine whether neuronal modulation was related to an unconditioned orienting response that occurred concurrently with the forelimb response. We have previously reported that these three tasks separate neurons in MCx whose modulation precedes the response (lead cells) into three distinct classes in which task-related activity either is correlated with the direction of the forelimb response, correlated with the stimulus, or not correlated with either (Martin and Ghez 1985). All lead cells, however, remained timed to the stimulus rather than to the response. The present results show that RN lead cells can be subdivided into the same three classes as those in MCx and their discharge was also contingent on the subsequent production of a behavioral response. (1) Force-direction neurons (35%; n = 16) showed changes in activity correlated with the production of forearm force in a particular direction suggesting that they could participate in selecting the appropriate forelimb response. The onset of task-related modulation of activity was better timed to the response, in contrast to force-direction neurons in MCx, which were better timed to the stimulus. (2) Stimulus-direction neurons (18%; n = 8) modulated their activity in relation to a particular stimulus evoking either flexor or extensor responses and during neck task performance. These neurons could be involved in processing stimulus information or in the production of neck torque. The task-related discharge of these lead cells was better timed to the stimulus than to either the forelimb or the neck response. (3) Nondirectional neurons (47%; n = 21) modulated their activity during all tasks examined. Their discharge did not correlate with any specific feature of the stimulus or response, and as a group, was better timed to the stimulus than to the response. Nondirectional neurons may participate in some aspect of motor preparation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Modulation by oestrogen and progestins/antiprogestins of alpha interferon receptor expression in human breast cancer cells.

Human breast cancer ZR-75-1 cells expressed 1516 (105) (mean [S.D.]) interferon (IFN) receptors (IFNR) per cell with Kd of 0.61 (0.15) nmol/l. Oestrogen independent ZR-PR-LT and tamoxifen resistant ZR-75-9a1 8 mumol/l cells expressed similar numbers of IFNR. ZR-75-9a1 cells, which had been maintained in the absence of tamoxifen or known oestrogenic activity for 46 weeks, expressed a significantly higher number of IFNR (3170 [315]). Exposure of ZR-75-1 cells to 10(-9) mol/l 17 beta-oestradiol (E2) led to a consistent reduction in IFNR numbers whilst 10(-6) mol/l tamoxifen slightly increased IFNR expression. Since IFN increases oestrogen receptors in this cell line, IFN and E2 appear to have opposite effects on expression of each others' receptor. 10(-9) mol/l medroxy progesterone acetate and mifepristone significantly increased IFNR numbers whilst ORG 2058 decreased IFNR expression and ZK 98.299 had no effect. Progestin/antiprogestin induced IFNR increase in this cell line correlated with down-regulation of progesterone receptor (PR). Thus an IFN/ER/PR axis may exist in ZR-75-1 cells and variants.

Breast Neoplasms↗
PubMed1991

In vitro penetration of human corneal epithelium by Acanthamoeba castellanii: a scanning and transmission electron microscopy study.

Human corneal buttons were exposed to Acanthamoeba castellanii trophozoites and cysts for 12 hours at 35 degrees C. The buttons examined by light microscopy and scanning and transmission electron microscopy had severe epithelial ulceration and penetration by trophozoites. Observations on trophozoites below the surface suggest that penetration is accomplished by both secreted cytolytic enzymes and phagocytosis. It is likely that the secretion of one or more enzymes constitutes the initial step in preparing the host tissue for endocytosis or that the secretory mechanism is used by the amebas to move through the outer squamous layer to the basement epithelium where phagocytosis occurs. Based on this study and a previous study, it appears that entry into the cornea is a two-step process involving adherence and penetration by trophozoites.

Acanthamoeba↗
PubMed1991

In vitro intercellular adherence of Acanthamoeba castellanii: a scanning and transmission electron microscopy study.

Human corneal buttons were exposed to trophozoites and cysts of Acanthamoeba castellanii for 12 hours. Examination of the buttons by scanning electron microscopy showed numerous trophozoites on the surface of the epithelium. Trophozoites examined by transmission electron microscopy had limited regions of attachment to the epithelium but extensive regions of attachment to each other. Attachment regions were characterized as plaque-like maculae of an incomplete desmosome junction. Firm attachment mechanisms may explain how penetration of the human cornea occurs.

Acanthamoeba↗
PubMed1990

Ultrastructural and immunohistological characterization of the SIRC corneal cell line.

A widely utilized rabbit corneal cell line, SIRC, was characterized ultrastructurally and immunohistologically. Although SIRC cells are often described as being of epithelial origin, important ultrastructural and antigenic characteristics indicate that these cells are fibroblastic and not epithelial. SIRC cells lack desmosomes, cytoplasmic filaments, and cytokeratin-structures that are characteristic of corneal epithelial cells. By contrast, the dendritic morphology, presence of vimentin, and the extensive dense accumulations of ribosomes and rough endoplasmic reticulum are consistent with a fibroblastic phenotype. Collectively, the morphology, ultrastructural features, and antigenic composition favor the hypothesis that SIRC cells are fibroblastic cells (keratocytes) and not corneal epithelial cells.

Animals↗
PubMed1989

The ultrastructural immunocytochemical localization of superoxide dismutase in the amphibian urinary bladder: effect of aldosterone.

Transmission electron microscopy and immunohistochemistry, the latter employing the avidin-biotin-peroxidase (ABC complex) technique, were utilized to localize copper-zinc superoxide dismutase (CuZn-SOD) enzyme activity in the epithelial cells of the toad urinary bladder mucosa. This 'scavenger' enzyme catalyses the dismutation (reduction-oxidation) of the superoxide anion (O2-), a toxic free radical generated during normal cellular respiration. In unstimulated epithelial cells, enzyme activity was seen in the cytosol of granular, mitochondrial-rich and goblet cells. The basal cells were generally devoid of enzyme activity. In addition to the cytosol, SOD activity was also seen in association with the apical plasma membrane of the epithelial cells. In the presence of the steroid hormone aldosterone (10(-7)M, 30 min-6h), CuZn-SOD activity was markedly increased along the luminal mucosal membrane of granular, mitochondrial-rich and goblet cells. This increase was seen as early as 30 min after the addition of hormone, and as long as 6h after treatment. The cytosolic reaction was usually decreased or absent under these conditions. From the data presented, it appears that CuZn-SOD is involved in electrolyte (sodium) transport in the epithelial cells of the toad urinary bladder. The latter may involve hormone-induced alterations in luminal cell membrane structure and chemistry.

Aldosterone↗
PubMed1988

Electron microscopic cytochemical localization of Ca-ATPase in the rod outer segments of the toad Bufo marinus.

Transmission electron microscopy and ultracytochemistry were employed in an attempt to localize the enzyme calcium adenosine triphosphatase (Ca-ATPase) in the rod outer segments (ROS) of the toad retina. Utilizing a one-step incubation procedure, Ca-ATPase was identified as an electron-dense precipitate in the intradiskal spaces of the rod disks (vesicles) of the ROS. Analytical microscopy identified the reaction product as lead phosphate. The formation of the reaction product was dependent on the presence of ATP (the substrate) and calcium ions. However, calcium ions could be substituted for by magnesium ions. In addition, the reaction was vanadate sensitive. The latter is known to inhibit Ca-ATPase activity. Such data appear to indicate the presence of a Ca-Mg-ATPase in association with the rod disks. Since cyclic guanosine monophosphate (cyclic GMP), rather than calcium ions, is currently believed to be the primary intracellular messenger associated with phototransduction, the presence of an ROS Ca-ATPase may indicate other functions for this cation in the physiology and biochemistry of the visual process. Ca-ATPase might play a role in directional calcium fluxes between intracellular compartments.

Animals↗
PubMed1988

Degradation of DNA in cells and extracts of the obligately anaerobic bacterium Roseburia cecicola upon exposure to air.

High-molecular-weight chromosomal DNA from Roseburia cecicola, an oxygen-intolerant anaerobe, could be isolated only when the bacterial cells were kept under anaerobic conditions up to the time of cell lysis. When the cells were exposed to oxygen before lysis, the chromosomal DNA degraded. Likewise, linear but not covalently closed circular DNAs degraded in cell extracts of the organism that were exposed to atmospheres containing O2 but not in extracts that were maintained in a reduced state. Covalently closed circular DNAs were nicked but not degraded in the oxidized extracts.

Anaerobiosis↗
PubMed1988

Cloning, nucleotide sequence, and taxonomic implications of the flagellin gene of Roseburia cecicola.

The gene coding for the flagellin protein of Roseburia cecicola, an oxygen-intolerant, gram-negative, anaerobic bacterium indigenous to the murine cecum, has been cloned and sequenced. NH2-terminal amino acid sequence data from the flagellin protein were used as a basis for the synthesis of two mixed-sequence deoxyoligonucleotides. The oligonucleotides were used to identify and clone the flagellin structural gene. DNA sequence analysis of M13mp8 and mp9 subclones revealed a protein with a length of 293 amino acids and a molecular weight of 31,370. Comparisons with the sequences of flagellins of other species revealed conserved regions and suggested that although R. cecicola has structural characteristics of a gram-negative bacterium, it may be most closely related to the gram-positive bacteria.

Amino Acid Sequence↗
PubMed1988

Effect of poly(adenosinediphosphoribose) synthesis inhibitors and structurally related compounds on radiation-induced G2 arrest.

A variety of poly(adenosinediphosphoribose) p(ADPR) synthesis inhibitors, structurally related compounds with no inhibitory activity, and agents which reduce radiation-induced G2 arrest, were tested for the concentration dependence of their effect on (a) CHO cell progression to mitosis, (b) the duration of G2 arrest in X-irradiated CHO cells and (c) [14C]NAD incorporation in permeabilized CHO cells, as a measure of p(ADPR) synthetase activity. Caffeine and nicotinamide uptake by viable cells was also measured. The concentration dependencies for reduction of radiation-induced G2 arrest and for p(ADPR) synthesis inhibition were markedly disparate, although all of the active inhibitors of p(ADPR) synthesis did reduce the duration of radiation-induced G2 arrest to some extent. These data indicate that p(ADPR) synthesis is not a requirement for the induction of G2 arrest by ionizing radiation.

Aminobenzoates↗
PubMed1987

Electron microscopic cytochemical localization of a basolateral calcium adenosine triphosphatase in vitamin D replete chick enterocytes.

A cytochemical technique for the electron microscopic localization of calcium adenosine triphosphatase (Ca-ATPase) was utilized to localize this enzyme in the enterocytes of rachitic and vitamin D-replete chicks. In animals treated with cholecalciferol (CC, vitamin D3), an electron-dense reaction product was located along the basolateral membranes of the absorptive cells within 72 hr after injection. Similarly, a reaction product was identified in association with the basolateral membranes within 24 hr after injection of 1,25-dihydroxycholecalciferol, the active metabolite of vitamin D. A microvillar reaction product was not seen in either of these two groups. Electron-dense reaction products were also seen in association with mitochondria and scattered throughout the cytoplasm of these enterocytes. The Ca-ATPase reaction product was dependent upon the presence of medium calcium and substrate (ATP), was inhibited by vanadate, and was heat labile. In the rachitic animals, a reaction product indicative of Ca-ATPase activity was not seen in association with either the basolateral membranes or the mitochondria. These data appear to indicate that an energy-requiring calcium-activated membrane pump plays a role in the flux of calcium across the enterocytes of the small intestine.

Animals↗
PubMed1986

Cardiac dysrhythmias associated with ophthalmic atropine.

Atropine sulfate, a mydriatic and cycloplegic agent, is frequently used in patients undergoing glaucoma surgery. Trabeculectomy with peripheral iridectomy is the most common glaucoma surgery performed to decrease intraocular pressure and preserve vision. Systemic absorption of ophthalmic atropine does occur and may result in toxic and adverse side effects. Cardiac dysrhythmias are one of the major adverse reactions. This case study reviews three patients who had a trabeculectomy for glaucoma and received ophthalmic atropine. One patient received both systemic and ocular atropine. Two patients developed atrial fibrillation and one a supraventricular tachycardia. Two patients required admission to a cardiac intensive care unit for management of the dysrhythmia and a third reverted to normal sinus rhythm spontaneously. The cardiac effects of ophthalmic atropine should be considered in the preoperative and postoperative assessment of patients with dysrhythmias.

Absorption↗