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Biomedical subjects

J L Ricci

Publications and source records attributed to J L Ricci.

29 records · Page 2Linked to original sources
PubMed1990

A new canine model to evaluate the biological response of intramedullary bone to implant materials and surfaces.

A new canine model utilizing an implantable chamber with multiple bone ingrowth channels has been used to study the response of intramedullary bone to various implant materials and surfaces. The first group of dogs received implants containing channels lined by smooth-surfaced coupons of titanium, titanium alloy, sputter-hydroxyapatite-coated (HA-coated) titanium alloy, and polyethylene. A pattern of early initial bone ingrowth by 2 weeks, becoming maximal at 6 to 12 weeks with remodeling to a more mature lamellar bone, and later resorption by 24 weeks was seen for all test groups, with fibrous tissue interfaces covering the smooth test coupons at all time points. Significantly increased bone ingrowth in the sputter-HA coated group was found only at 6 weeks. The second group of dogs received implants with channels lined by surface-roughened coupons of either titanium or plasma-HA-coated titanium, half of which were also packed with a crystalline-HA grouting at the time of surgery. At both 6 and 12 weeks, bone ingrowth was greatly enhanced by the presence of the plasma-HA coating or the crystalline-HA grouting as compared to the uncoated titanium channels. Histologically, bone was seen to bond directly to the plasma-HA coating and the crystalline-HA grouting. A thin fibrous tissue layer was noted between bone and the titanium in most areas, but evidence of direct bone contact to the metal surface was seen. Mechanical testing in tension of intact coupon-bone-coupon units revealed significant strength of the bone-plasma-HA bond, with failure initiating at the metal-HA interface with forces of 15.3 N at 6 weeks, increasing to 44.8 N at 12 weeks. Plasma-HA-lined channels with crystalline-HA packing required similar forces for failure. No significant adhesion strength was noted for the titanium channels at 6 weeks, and only the crystalline-HA-filled channels displayed measurable strength of the bone-titanium interface at 12 weeks, with a force of 9 N needed for failure.

Animals↗
PubMed1990

A new canine model to evaluate the biological effects of implant materials and surface coatings on intramedullary bone ingrowth.

A new animal model for examining the intramedullary bone response to various implant materials and surfaces is presented, utilizing an implantable chamber with multiple bone ingrowth channels placed through a cortical defect in the lateral aspect of the distal femur. Twelve adult mongrel dogs received bilateral implants containing channels lined by smooth-surfaced coupons of titanium, titanium alloy, sputter-hydroxyapatite-coated titanium alloy, and UHMW polyethylene. A pattern was detected for all test groups of early initial bone ingrowth by two weeks, which became maximal at six to twelve weeks, followed by remodelling to a more mature lamellar bone and later resorption by 24 weeks, with fibrous tissue interfaces covering the smooth test coupons of all groups at all times. Significantly increased bone ingrowth in the sputter-HA coated group was found only at six weeks.

Animals↗
PubMed1989

Spontaneous gastroduodenal perforation in cancer patients receiving cytotoxic therapy.

Spontaneous gastroduodenal perforation (SGDP) occurs in cancer patients receiving cytotoxic drugs, corticosteroids, or radiation therapy as primary or adjuvant treatment for their tumors. A retrospective review identified 12 patients from 1974 to 1987 at the Memorial Sloan-Kettering Cancer Center who underwent surgery for SGDP while receiving anticancer therapy. There were five gastric and seven duodenal perforations. Vague abdominal pain was the most common symptom. Exploration was delayed in six patients because of an absence of physical findings. All patients received a Graham omental patch. The in-hospital operative mortality was 33%, with all major complications occurring in those that died. There were no prognostic indicators identified that would preoperatively predict outcome. Aggressive surgical intervention is advised in all patients who have a reasonable chance of worthwhile palliation if not cure.

Adrenal Cortex Hormones↗
PubMed1989

Hydroxyapatite ceramics and the nature of the bone-ceramic interface.

Hydroxyapatite ceramics have been used as bone implants in a number of experimental systems and clinical applications. We have developed a unique experimental model that allows study of the interface between bone and implant materials. A comparison of titanium and hydroxyapatite materials, using this model, has demonstrated the osteoconductive nature of hydroxyapatite and its ability to bond directly to bone.

Animals↗
PubMed1988

Osteoconductive composite grouts for orthopedic use.

A composite of HA particulate and calcium sulfate hemihydrate has been developed. When this dry material is mixed with either sterile saline or water, the resulting mixture begins to gel. While in the gel or dough state, the composite can be manually inserted or injected under pressure into a bone defect where it sets in situ. The calcium sulfate acts as a binder to hold the HA particles in place. The subsequent resorption of the calcium sulfate leaves controlled porosity for bone ingrowth and attachment to the nonresorbable HA particulate. The combination of calcium sulfate and HA results in a composite with handling properties superior to those of HA alone. Calcium sulfate has a long history of medical use as an implant material. The biocompatibility of the material has been clearly established. The combination of HA and calcium sulfate is likewise extremely compatible as demonstrated in the present studies. Bone ingrowth concomitant with resorption occurs rapidly with efficient conduction of bone from particle to particle. Based on the experiments presented herein, the composite of HA and calcium sulfate may be a useful alternative or adjunct to autogenous bone grafting. Many questions, however, remain regarding long-term tissue response and bone remodeling as well as the efficacy of this material relative to bone grafting.

Alveolar Process↗
PubMed1985

Intestinal ischemia: reduction of mortality utilizing intraluminal perfluorochemical.

This study reports an assessment of a method of intestinal protection by the intraluminal administration of an oxygenated perfluorochemical, perfluorotributylamine, or gaseous oxygen in an attempt to provide oxygen for mucosal cells rendered ischemia. A model of acute arterial or acute arteriovenous ischemia was produced in adult female rats. All control ischemic animals died within 12 hours. To assess intestinal protection, the mortality rates in the experimental groups were compared with the 100 percent control mortality. Gaseous oxygen and oxygenated perfluorochemical administered intraluminally reduced mortality significantly in the acute arterial model but not in rats with arteriovenous occlusion. Electron microscopy demonstrated preservation of villi after 1 and 2 hours of occlusion in the oxygen-treated groups. Light microscopy revealed massive destruction in control animals with preserved architecture in both the gaseous oxygen and oxygenated perfluorochemical groups. These results demonstrate that the intraluminal delivery of oxygen to bowel rendered ischemic by arterial occlusion may significantly decrease anatomic bowel disruption and improve animal survival. Such techniques have a potential clinical application to facilitate salvage of ischemic intestine and to augment intestinal preservation.

Animals↗
PubMed1984

Immunodepression secondary to malnutrition: assay by lymphocyte subset analysis using monoclonal antibodies and the cell sorter.

It has been well documented that the hospitalized child frequently is malnourished, and the considerably greater morbidity and mortality of such children, in large part, is due to the associated secondary immunodepression. To assess the mechanism of such immunodepression in acute and chronically malnourished subjects, we chose an experimental murine model of malnutrition. Immune function was assayed by lymphocyte subset population and mixed lymphocyte culture (MLC) assessment, determining whether an alteration of the T helper (TH) to T suppressor-cytotoxic (TS-C) lymphocyte ratio is the mechanism that produces immunoincompetence in malnutrition. Ten-week-old A/J mice were rendered acutely or chronically malnourished by graded protein restriction using a 2.5% protein diet. These animals were studied before and after protein depletion with the fluorescent activated cell sorter (FACS) and the MLC. FACS cell populations were defined by the monoclonal antibodies to THY 1.2, LYT 1 (TH), and LYT 2 (TS-C) antigens. MLC reactivity was assessed with A/J v C 57 BL/6 mouse lymphocytes and expressed as a stimulation index (S.I.). Results are expressed in Table 1, and suggest that these malnourished animals were significantly immunodepressed as measured in the MLC reaction. However, the mechanism of this depression is not mediated by an inversion of the TH/TS-C ratio. These data contrast with those previously reported for the immunodepression of the burned or traumatized patient in which the TH/TS-C ratios are reversed; these data suggest that a different, as yet to be elucidated, mechanism exists for the immunodepression of malnutrition.

Animals↗
PubMedDate not supplied

Morphological characteristics of tendon cells cultured on synthetic fibers.

Filamentous carbon is currently being used as an implant material for tendon and ligament repair in humans. This material acts as a scaffold for the organization of new fibrous tissue growth. Primary cultures of rat tendon fibroblast cells (1 degrees RTF cells) were grown on carbon, Dacron, polyethylene and Nylon fibers in vitro. The morphological characteristics of these cells were examined. The process of cell migration from tendon explant to fiber substrate was similar for all four materials. Three morphological categories of cells were observed on these materials. (1) spherical dividing cells, (2) spindle-shaped migrating cells, (3) sheath-like migrating or stationary cells. The morphological characteristics and orientational behavior of cultured fibroblasts on these fiber materials were strongly influenced by the diameters of the fibers and by fiber surface characteristics such as longitudinal striations. The possible mechanisms of cell response to substrate geometric configuration are discussed along with the clinical significance of these experiments.

Animals↗
PubMedDate not supplied

A neuromuscular platform to extract electrophysiological signals from lesioned nerves: a technical note.

The volitional control of prosthetic devices could be greatly enhanced if the information formerly supplied by peripheral nerves to the amputated limb could be utilized. So that practical access to this information could be gained, a method was established to form a stable biological interface with fascicles of lesioned nerves. A small strip of an intact muscle was isolated in rats with the use of a silicone tube cuff electrode and innervated by the lesioned peroneal branch of the sciatic nerve. After 4 weeks survival, stimulation of the nerve fascicle produced reliable signals from the neuromuscular platform in the range of 0.5 to 2.0 mV. Histologically, myotubes remained intact and axons could be identified growing in and over the surfaces of the isolated muscle strips. These or similar interface techniques may supply electrophysiological signals of sufficient amplitude and reliability to provide peripheral nerve-based guidance information for prosthetic devices.

Animals↗