Biomedical subjects

L M Patterson

Publications and source records attributed to L M Patterson.

9 recordsLinked to original sources

PubMed1998

Metal release in patients who have had a primary total hip arthroplasty. A prospective, controlled, longitudinal study.

UNLABELLED: There is an increasing recognition that, in the long term, total joint replacement may be associated with adverse local and remote tissue responses that are mediated by the degradation products of prosthetic materials. Particular interest has centered on the metal-degradation products of total joint replacements because of the known toxicities of the metal elements that make up the alloys used in the implants. We measured the concentrations of titanium, aluminum, cobalt, and chromium in the serum and the concentration of chromium in the urine of seventy-five patients during a three-year prospective, longitudinal study. Twenty patients had had a so-called hybrid total hip replacement (insertion of a modular cobalt-alloy femoral stem and head with cement and a titanium acetabular cup without cement), fifteen had had insertion of an extensively porous-coated cobalt-alloy stem with a cobalt-alloy head and a titanium-alloy socket without cement, and twenty had had insertion of a proximally porous-coated titanium-alloy stem with a cobalt-alloy head and a titanium socket without cement. The remaining twenty patients did not have an implant and served as controls. The results of our study showed that, thirty-six months postoperatively, patients who have a well functioning prosthesis with components containing titanium have as much as a threefold increase in the concentration of titanium in the serum and those who have a well functioning prosthesis with cobalt-alloy components have as much as a fivefold and an eightfold increase in the concentrations of chromium in the serum and urine, respectively. The predominant source of the disseminated chromium-degradation products is probably the modular head-neck junction and may be a function of the geometry of the coupling. Passive dissolution of extensively porous-coated cobalt-alloy stems was not found to be a dominant mode of metal release. CLINICAL RELEVANCE: Increased concentrations of circulating metal-degradation products derived from orthopaedic implants may have deleterious biological effects over the long term that warrant investigation. This is a particularly timely concern because of recent clinical trends, including the reintroduction of metal-on-metal bearing surfaces and the increasing popularity of extensively porous-coated devices with large surface areas of exposed metal. Accurate monitoring of the concentrations of metal in the serum and urine after total hip replacement also can provide insights into the mechanisms of metal release. Our findings suggest that fretting corrosion at the head-neck coupling is an important source of metal release that can lead to increased concentrations of chromium in the serum. Determinations of the concentrations of metal in the serum and urine may be useful in the diagnosis of patients who are symptomatic after a total joint replacement as increased levels are indicative of at least one mode of mechanical dysfunction (for example, fretting corrosion) of the device.

Adult↗

PubMed1997

Capsaicin-resistant vagal afferent fibers in the rat gastrointestinal tract: anatomical identification and functional integrity.

The presence and distribution of vagal fibers and terminals throughout esophagus and gastrointestinal tract that could be anterogradely labeled by nodose ganglion tracer injections was quantitatively assessed in capsaicin- and vehicle-pretreated adult rats, in order to identify the capsaicin-resistant population. Up to 90% of the intraganglionic laminar endings (IGLEs), in the myenteric plexus of the esophagus, and 70-90% in the stomach, as well as 57% of the intramuscular endings or arrays (IMAs) in the fundic stomach survived the capsaicin treatment, while in the upper small intestine only few and in the lower small intestine, the cecum and colon, virtually no IGLEs survived capsaicin treatment. Intramucosal terminals were not assessed. Furthermore, gastric balloon distension-induced c-Fos expression in the dorsal vagal complex was not significantly decreased in capsaicin-treated rats. It is concluded that among primary vagal afferents there is a capsaicin-resistant population that primarily innervates the esophagus and upper gastrointestinal tract, and a capsaicin-sensitive population that innervates mainly the lower tract. At least vagal gastric tension-sensitive afferents also seems to be functionally intact in that they may be capable of synaptically activating second-order neurons in the brainstem.

Animals↗

PubMed1997

Distribution and structure of vagal afferent intraganglionic laminar endings (IGLEs) in the rat gastrointestinal tract.

Intraganglionic laminar endings (IGLEs) are special terminal structures of vagal afferent fibers and have been demonstrated in the myenteric plexus of esophagus and stomach. In order to quantitatively map their presence and distribution over the entire gastrointestinal tract, including the small and large intestines, vagal afferents were anterogradely labeled in vivo by microinjections of the fluorescent carbocyanine dye DiI into the left or right nodose ganglion of adult male rats. In the most successfully labeled cases the highest density of IGLEs was found in the stomach, with about half to one-third of the myenteric ganglia receiving at least one IGLE. The proportion of myenteric ganglia innervated by IGLEs decreased in the small intestine; however, because of its large surface area this gut segment was estimated to contain the highest total number of IGLEs. Both the cecum and colon also contained significant numbers of IGLEs. In the stomach, this vagal afferent innervation by IGLEs was more or less lateralized, with less than 20% of labeled IGLEs found on the contralateral side with respect to the injection. The left/ventral vagus contributed a larger proportion of IGLEs to the proximal duodenum, while the right/dorsal vagus contributed a larger proportion of IGLEs to the distal duodenum and jejunum. Laser scanning confocal microscopy on select specimens revealed further structural details. The parent axon typically formed two or more branches that flanked the ganglia laterally, and in turn produced numerous highly arborizing laminar terminal branches that covered one or both flat sides of the ganglion in a dome-like fashion. The similar distribution patterns and structural details suggest a uniform function for the IGLEs throughout the gastrointestinal tract, but there is as yet no clear proof for any of the hypothesized roles as specialized mechanosensors or local effector terminals.

Animals↗

PubMed1997

Limited excitatory local effector function of gastric vagal afferent intraganglionic terminals in rats.

Intraganglionic laminar endings (IGLEs) are complex terminal structures of vagal afferent origin, distributed throughout the myenteric plexus of the esophagus and gastrointestinal tract and without a known function. They may serve local effector function by means of peripheral axon reflexes, analogously to dorsal root afferents. To test this possibility, vagal afferent fibers were antidromically activated by suprathreshold electrical stimulation of the cervical vagus nerve in anesthetized rats that underwent prior supranodose vagotomy, and responses of myenteric neurons were monitored with Fos immunocytochemistry. Stimulation of vagal afferents produced Fos expression in a slightly, but significantly, higher proportion of myenteric plexus neurons of the gastric corpus (1.02 +/- 0.21%, P < 0.05) and esophagus (1.59 +/- 0.46%, P < 0.05) than in control animals with sham-stimulation (corpus, 0.12 +/- 0.05%; esophagus, 0.18 +/- 0.18%). Stimulation of vagal efferents produced widespread Fos induction in myenteric neurons. Given the many enteric neurons in close anatomic contact with IGLEs and the low proportion of Fos activated neurons after selective afferent stimulation, the results do not support a widespread excitatory local effector function of IGLEs. However, inhibitory effects and/or weak excitatory synaptic inputs that do not engage Fos expression cannot be ruled out.

Analysis of Variance↗

PubMed1996

Innervation of rat abdominal paraganglia by calretinin-like immunoreactive nerve fibers.

The extended hepatic pedicle of the rat containing the vagal hepatic branch and associated paraganglia was dissected as whole mount, processed for calretinin immunocytochemistry, and analyzed by laser-scanning confocal microscopy. About half of the 8-12 paraganglia of the region were innervated to a various degree by calretinin-immunoreactive (CAL-IR) nerve fibers that formed basket-like varicose terminals around small clusters of glomus tissue. Neither the numerous capillaries, nor the occasional non-CAL-IR neuron accompanying some paraganglia, were recipients of CAL-IR terminals. In animals with prior left cervical vagotomy the number of CAL-IR fibers was decreased but not abolished. Since about 30% of neurons in the nodose ganglia, a few neurons within the vagal hepatic branch/hepatic hilus area, and numerous neurons in the gastric myenteric plexus were CAL-IR, these neurons represent other potential sources of CAL-IR innervation of the paraganglia.

Animals↗

PubMed1996

Anatomical relationship between vagal afferent fibers and CCK-immunoreactive entero-endocrine cells in the rat small intestinal mucosa.

There is evidence for a pathway involving small intestinal CCK-producing entero-endocrine cells and visceral afferent nerve fibers in signaling the effect of luminal nutrients on gastrointestinal and food intake regulation. In order to investigate the type of anatomical apposition that exists between CCK cells and vagal afferents, CCK immunocytochemistry was performed on tissue from rats whose vagal afferent fibers to the abdomen had previously been labeled in vivo by injecting the fluorescent carbocyanine dye DiI into the nodose ganglia. CCK immunoreactive (CCK-IR) cells were more abundant than vagal afferent fibers, but both were present throughout the small intestine as well as in crypts and villi. Few CCK-IR cells were in close (< 5 microns) anatomical contact with vagal afferent axons, and the latter did not produce suspicious terminal specializations near CCK-IR cells. Most labeled vagal afferent axons, which distributed strictly within the crypt and villous lamina propria, were at distances of tens to hundreds of microns to the nearest CCK-IR cell. These findings strongly support the idea that CCK released from entero-endocrine cells acts on vagal sensory fibers in a paracrine fashion, but do not rule out the presence of a few very close, neurocrine-like contacts or a humoral mode of action. Possible implications of such an arrangement on CCK-mediated satiety are discussed.

Afferent Pathways↗

PubMed1993

Adaptation six months after multiple trauma: a pilot study.

This pilot study investigated the functional and psychosocial adaptation of 18 survivors of multiple trauma who were in the home setting 6 months after discharge from a tertiary trauma center. Seventeen subjects reported complete functional independence and one reported the need for assistance with self-care activities as measured by the Modified Barthel Index. All subjects reported problems with psychosocial adaptation as measured by the Psychosocial Adjustment to Illness Scale (PAIS). Subjects with high PAIS scores (worst adaptation) reported problems in all domains of the PAIS, whereas those with low PAIS scores (best adaptation) reported most problems in health care orientation. Mann-Whitney U tests were significant for gender, household composition and employment status when compared with low PAIS scores (p < 0.05). An analysis of variance confirmed employment status was the best predictive factor for low PAIS scores.

Abbreviated Injury Scale↗

PubMedDate not supplied

Diabetes insipidus versus syndrome of inappropriate antidiuretic hormone.

Diabetes insipidus (DI) and the syndrome of inappropriate antidiuretic hormone (SIADH) are two endocrine disorders presenting a challenge to the critical care nurse. The challenge lies in the recognition and assessment of the effects on the patient's fluid balance and in the planning of interventions to prevent complications.

Diabetes Insipidus↗

PubMedDate not supplied

Implementation of a pain management program in a community hospital.

Literature reports and staff concerns about management of patients' pain prompted nurses in a 337-bed suburban community hospital to implement a pain management education program. The Task Force tackled physician collaboration, securing resources, revising documentation tools, and designing an educational workshop. Their efforts resulted in the purchase of audiovisual materials for staff and patient use, addition of information about patient-controlled analgesia (PCA) devices to the hospital closed-circuit patient education TV channel, distribution of the Agency for Health Care Policy and Research (AHCPR) guidelines to hospital staff, revision of documentation tools, and the implementation of a 4-hour pain management education workshop for all professional nurses. Quality monitoring after the workshop reflected an improvement in nursing documentation of pain management.

Analgesia, Patient-Controlled↗