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Biomedical subjects

J N Riley

Publications and source records attributed to J N Riley.

At least 19 recordsLinked to original sources
PubMed2001

New range of light-activated surgical adhesives for tissue repair.

A new range of light-activated surgical adhesives has been developed for laser-assisted tissue repair. The surgical adhesive is composed of a polymer scaffold doped with the traditional protein solder mix of serum albumin and a chromophoric dye. Problems associated with inflexibility in conforming to various tissue geometries, instability in a hydrated environment due to non-uniform tissue adhesive denaturation, and solubility in physiological fluids prior to denaturation are overcome using the adhesives. The new adhesives offer a viable alternative to conventional fasteners, including sutures, staples and clips, currently used for tissue repair. In addition, it could be possible to use patches prepared from the adhesive in the field as a simple and effective method to stop bleeding and repair tissue quickly in an emergency situation. First, studies were conducted to improve the flexibility of traditional protein solders to enable them to be tailored to a wide range of clinically relevant geometry's including tubes, crescents and tape. Second, the creation of a chromophore concentration gradient across the thickness of the adhesive was investigated as a means to allow control of the heat source gradient through the adhesive. Increased deposition of the laser energy near the vital solder/tissue interface was thus achieved. Finally, predenaturation of the adhesive was investigated as a means for enhancing its stability in a hydrated environment thus improving the handling characteristics of the adhesive for clinical application. The application of the new surgical adhesives to augment laser tissue repairs is shown to enhance edge co-optation, improve repair strength and to reduce thermal tissue injury. The moldable, absorption controllable and flexible nature of the new adhesives greatly improves the clinical applicability of laser-solder tissue repair.

Animals↗
PubMed2001

Improved laser-assisted vascular tissue fusion using light-activated surgical adhesive in a porcine model.

Newly developed light-activated surgical adhesives have been investigated as a substitute to traditional protein solders for vascular tissue fusion without the need for sutures. Porcine carotid arteries (n = 6) and femoral arteries (n = 6) were exposed, and an incision was made in the arterial walls using a 16G needle. The surgical adhesive, composed of a poly(L-lactic-co-glycolic acid) scaffold doped with the traditional protein solder mix of porcine serum albumin and indocyanine green dye, was used to close the incisions in conjunction with an 805 nm diode laser. Blood flow was restored to the vessels immediately after the procedure and the incision sites were checked for patency. The new adhesives were flexible enough to be wrapped around the vessels while their solid nature avoided the problems associated with "runaway" of the less viscous liquid protein solders widely used by researchers. The strength and hemostatic abilities of the new surgical adhesives were evaluated in the context of arterial pressure, persistence of hemostasis and presence of any inflammatory reaction after 3 days. After this evaluation period, the surgical procedure was repeated on the carotid arteries (n = 6) and femoral arteries (n = 6) of three additional animals that had been heparinized prior to surgery to closer approximate the conditions seen in a typical vascular surgical setting. The patency rate of both the unheparinized and heparinized vessels was 100% at 3 days post-operative with evidence of intraluminal thrombosis seen in only one of the repaired vessels. The adhesive technique also compared favorably with a previous study conducted using conventional suture techniques. Repairs formed with the adhesive technique were achieved more rapidly than suturing, and acute leakage was observed less frequently. Finally, the adhesive technique produced better histology than the suture technique, suggesting that it has great promise as an alternative to suturing. These initial results indicate that laser-assisted vascular repair using the new adhesives is safe, easy to perform, and contrary to conventional suturing, provides an immediate leak-free closure. In addition, the flexible and moldable nature of the new adhesives allows them to be tailored to a wide range of tissue geometries, thus greatly improving the clinical applicability of laser-assisted tissue repair.

Animals↗
PubMed1986

The motor trigeminal nucleus of the rat: analysis of neuronal structure and the synaptic organization of noradrenergic afferents.

The organization of the rat motor trigeminal nucleus (MTN) and the morphology of noradrenergic afferents terminating in this cranial motor nucleus were analyzed with light and transmission electron microscopy. Two morphologically distinct types of neurons are present in the MTN. Large multipolar neurons are the most prevalent cell type and are distributed uniformly throughout the nucleus. The morphology of these cells is identical to that of motor neurons described previously in both the brainstem and spinal cord. The neurons are characterized ultrastructurally by a light, organelle-rich cytoplasmic matrix containing numerous cisternal arrays of rough endoplasmic reticulum (RER) and a centrally placed spherical nucleus containing a single prominent nucleolus. Approximately 80% of the surface of these cells is contacted by axon terminals. The second major class of neuron consists of small spherical and fusiform cells that are located predominantly at the peripheral borders of the MTN. These cells are significantly smaller than motor neurons and exhibit only scattered axosomatic contacts. This small cell population appears to be composed of two distinct subclasses of neurons that probably represent interneurons and gamma motor neurons. The MTN neuropil contains four morphologically distinct classes of axon terminals that are characterized by either spherical or pleomorphic vesicles within cytoplasm that is lucent or dense. Quantitative morphometric analysis demonstrated differential distribution of each of the four terminal types upon motor neuron somata and dendrites. Intracerebral injection of 5-hydroxydopamine into the brainstem tegmentum immediately adjacent to the MTN labeled axon terminals containing spherical vesicles and a lucent axoplasmic matrix. Intracerebral injection of the neurotoxin 6-hydroxydopamine resulted in degeneration of the same terminal population and thus confirmed that noradrenaline-containing axons innervating the MTN exhibit a distinctive terminal morphology. The number of synaptic complexes exhibited by noradrenergic terminals did not differ significantly from other terminal populations in the MTN.

Animals↗
PubMed1981

A new microelectrophoretic procedure for delivery of horseradish peroxidase.

A new procedure for microelectrophoretic delivery of horseradish peroxidase (HRP) is described. A dilute solution (1.5--3% w/v) of fluorescein isothiocyanate-conjugated HRP is deposited according to a standard microelectrophoretic method and the tissue reacted according to a sensitive histochemical procedure. A major advantage of this method is the reduced secondary diffusion of the enzyme present at the injection site.

Animals↗
PubMed1981

A retinal projection to the lateral hypothalamus in the rat.

This study presents evidence for a retinal projection to neurons in the lateral hypothalamic area (LHA) of the albino rat. In Golgi-Kopsch material dendrites from LHA-neurons are observed to extend through the supraoptic commissures into the optic tract. The presence of dendrites in the optic tract is confirmed by electron microscopy. Numerous axon terminals are observed forming asymmetric synaptic contacts with these dendritic profiles. Following bilateral enucleation, many of the preterminal axons and terminals in synaptic contact with dendrites in the optic tract demonstrate dark degeneration. After intraocular injection of horseradish peroxidase, there is marked labeling of preterminal axons and terminals in the optic tract. These observations indicate that LHA neurons receive a direct retinal projection from terminals making synaptic contact with dendrites of LHA-neurons extending into the optic tract.

Animals↗
PubMed1980

Interpeduncular nucleus afferents in the rat.

Afferents to the interpeduncular nucleus (IPN) of the rat were studied with the horseradish peroxidase (HRP) retrograde transport method. HRP was deposited microelectrophoretically in the IPN of adult rats. Major projections to the IPN originate in the medial habenular nucleus, the region surrounding the dorsal tegmental nucleus (accessory dorsal tegmental nucleus and the so-called dorsal tegmental nucleus pars lateralis), and the midbrain raphe (nucleus centralis superior and nucleus raphe dorsalis). Also, minor projections originate in the central gray and nucleus locus coeruleus. Our results indicate that the habenulointerpeduncular projection originates solely from the medial habenular nuclei and is topographically organized; medial regions of the medial habenular nuclei project to ventral portions of IPN and lateral regions project to the dorsal IPN.

Afferent Pathways↗
PubMed1978

The islands of Calleja: organization and connections.

The islands of Calleja (IC) in the rate are composed of seven small groups of granule cells in the polymorph layer of the olfactory tubercle and one large group, the insula magna, which lies along the border between septum, nucleus accumbens and nucleus of the diagonal band. The cytoarchitecture and neuronal morphology of the IC and surrounding cells, studied using Nissl-stained and Golgi-Kopsch material, are described. In addition, the afferent and efferent connections of the IC were analyzed using fluorescence histochemistry, the autoradiographic tracing method, and the anterograde and retrograde horseradish peroxidase methods. Topographically organized projections to the IC from the dopamine-containing cells of the substantia nigra-ventral tegmental area are demonstrated by the glyoxylic acid fluorescence histochemical method and the autoradiographic tracing technique. Anterograde and retrograde horseradish peroxidase studies provide evidence for reciprocal, topographically organized interconnections between the IC and the septum, nucleus accumbens, amygdala and piriform cortex. These observations indicate that the IC constitute a unique population of granule cells, located in the olfactory tubercle, innervated by dopamine neurons of the mesencephalon and interconnected with olfactory and non-olfactory components of the basal forebrain.

Animals↗
PubMed1978

Morphological alterations in hippocampus after long-term alcohol consumption in mice.

Golgi methods were used to examine the hippocampus of laboratory mice that received alcohol-containing or control diets for 4 months followed by a 2-month alcohol-free period. Long-term alcohol consumption resulted in a significant loss of dendritic spines on hippocampal pyramidal cells and dentate granule cells. This study provides evidence that long-term alcohol consumption, in the absence of malnutrition, produces morphological damage to the central nervous system.

Alcoholism↗
PubMed1978

Ethanol dependence in the rat: role of non-specific and limbic regions in the withdrawal reaction.

Chronic bipolar electrodes were implanted in cortical, limbic, diencephalic and mesencephalic regions of the rat. Following recovery from surgery the rats were maintained for 14--26 days on a liquid diet in which 35--42% of total calories were provided by ethanol. Following ethanol withdrawal, electrographic and behavioral monitoring was continued for 8--10 h. The withdrawal of ethanol resulted in the time-dependent appearance of a variety of withdrawal signs including tail arching, ataxia, rigidity, tremor and spontaneous and audiogenic convulsions. These behavioral signs were accompanied by the development of epileptiform abnormalities across wide-spread brain regions. Analysis of preconvulsive spike activity revealed a greater spike frequency in limbic, mesencephalic and non-specific diencephalic regions, as compared to those in cortex and specific diencephalon. Seizure discharge during the tonic-clonic phase of the primary audiogenic convulsion was initiated in the mesencephalon or amygdala, but spread rather extensively to the remainder of the brain. In those instances, however, where multiple convulsions occurred following the audiogenic convulsions, there was a marked decline in spread of seizure discharge to the cortex. These results were interpreted to support the notion that some degree of neuroanatomical specificity exists in the genesis of epileptiform abnormalities during ethanol withdrawal. A comparison of these results with those studying the neural mechanisms underlying other forms of generalized epilepsy was made. It is hypothesized that central pacemaking regions such as medial thalamus or reticular formation may serve to organize isolated epileptiform activity into coherent patterns of paroxysmal activity throughout the brain during the ethanol withdrawal syndrome.

Alcoholism↗
PubMedDate not supplied

Ethanol dependence in the rat: a parametric analysis.

Rats were maintained on liquid diets as their sole source of calories and fluid for 10, 15, 20, and 30 days. The diets consisted 35-40% of total calories in the form of ethanol. This procedure resulted in substantial ethanol intake leading to behavioral intoxication. Blood ethanol concentrations were found to be elevated throughout the day with a peak during the dark phase of the light cycle. The removal of ethanol resulted in evidence of physiological dependence, including behavioral manifestation of autonomic and somatic dysfunction and an increased susceptibility to audiogenic convulsions. Ten days of ethanol exposure was found to be sufficient for the reliable induction of ethanol dependence. Further increases in ethanol exposure resulted in increased hyperexcitability as measured by susceptibility to audiogenic convulsions. The severity of withdrawal behavior was found to be correlated with the blood ethanol concentration measured upon ethanol removal. A behavioral rating scale for the evaluation of alcohol withdrawal intensity in rats is described.

Animals↗
PubMedDate not supplied

A reliable Golgi-Kopsch modification.

A reliable Golgi-Kopsch variant is described. Tissue is fixed with 1% paraformaldehyde, 1% glutaraldehyde in 0.1 M phosphate buffer, pH 7.2. Tissue slabs (2.5--4 thick) are immersed for 5--7 days in a solution containing 3.5 g potassium dichromate, 15 g sucrose, 1.65 ml formaldehyde in 100 ml distilled water, washed briefly in 0.75% silver nitrate, and immersed in 0.75% silver nitrate for 2--3 days. Procedures for cutting, counterstaining, and handling sections are described.

Animals↗