In vivo evaluation of collagen-coated Dacron fiber in bone

To evaluate the influence of type I collagen and hydroxyapatite coatings on the ability of Dacron fiber to achieve biologic fixation to bone, tows with the following coatings were evaluated in vivo: avian collagen (A); an avian collagen/hydroxyapatite composite (AH); bovine tendon collagen (B); a bovine tendon collagen/hydroxyapatite composite (BH); and plain (uncoated) Dacron tow (C). The Dacron tows were placed unstressed in the cancellous bone of both lateral femoral condyles of rabbits. Tissue reaction to each kind of Dacron tow was evaluated histopathologically, histomorphometrically and biomechanically. Inflammatory reaction was apparent around the AH and BH Dacron fibers at 2 weeks. There was no such reaction in the A, B, and C specimens, thus implicating the hydroxyapatite particles as the cause. At later time periods specimens A, B, and C all induced new bone formation. Direct contact between the Dacron fibers and trabecular bone was apparent in A and B. The pull-out strength of the B fibers was higher than the controls at a statistically significant level, but there was no significant difference between any of the other specimens and C (controls). There was no significant difference between any coating and controls at 8 or 16 weeks. Dacron fibers coated with bovine tendon collagen exhibited the best biocompatibility to bone and improved the anchoring to bone in the early time intervals by maintaining direct contact between Dacron fibers and trabecular bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Delay in cooling negates the beneficial effect of mild resuscitative cerebral hypothermia after cardiac arrest in dogs: a prospective, randomized study

OBJECTIVE

Previously, we documented that mild hypothermia (34 degrees C) induced immediately with reperfusion after ventricular fibrillation cardiac arrest in dogs improves functional and morphologic cerebral outcome. This study was designed to test the hypothesis that a 15-min delay in the initiation of cooling after reperfusion would offset this beneficial effect.

DESIGN

Prospective, randomized, controlled study.

SETTING

Animal intensive care unit.

SUBJECTS

A total of 22 custom-bred coonhounds.

INTERVENTIONS

Eighteen dogs underwent normothermic ventricular fibrillation arrest (no blood flow) of 12.5 mins, reperfusion with brief cardiopulmonary bypass, defibrillation within 5 mins, intermittent positive-pressure ventilation to 20 hrs, and intensive care to 96 hrs. Three groups of six dogs each were studied: group 1, normothermic controls; group 2, core temperature 34 degrees C from reperfusion to 1 hr; and group 3, delayed initiation of cooling until 15 mins after normothermic reperfusion, and 34 degrees C from 15 mins to 1 hr 15 mins after cardiac arrest.

MEASUREMENTS AND MAIN RESULTS

Tympanic membrane temperature (which represented brain temperature) in group 2 reached 34 degrees C at 6 +/- 3 (SD) mins after reperfusion; and in group 3 at 29 +/- 1 mins after reperfusion. Best overall performance categories achieved (1, normal; 5, brain death) compared with group 1, were better in group 2 (p < 0.5) but not in group 3 (NS). Similar results were found with best neurologic deficit scores (0%, normal; 100%, brain death), i.e., 44 +/- 4% in group 1, 19 +/- 15% in group 2 (p < .01), and 38 +/- 9% in group 3 (NS). Total brain histologic damage scores (< 30 minimal damage; > 100 severe damage), however, were 150 +/- 32 in group 1, 81 +/- 13 in group 2 (p < .001 vs. group 1), and 107 +/- 17 in group 3 (p < .05 vs. group 1).

CONCLUSIONS

Mild, resuscitative cerebral hypothermia induced immediately with reperfusion after cardiac arrest improves cerebral functional and morphologic outcome, whereas a delay of 15 mins in initiation of cooling after reperfusion may not improve functional outcome, although it may slightly decrease tissue damage.

The effect of resuscitative moderate hypothermia following epidural brain compression on cerebral damage in a canine outcome model

A canine model of temporary epidural cerebral compression and standardized intensive care was developed to evaluate the effect of resuscitative (postinsult) moderate systemic hypothermia. A balloon was inflated over the temporal region to maintain contralateral intraventricular pressure (IVP) at 62 mm Hg for 90 minutes. For a 66-hour period after initiation of brain compression, the intubated dogs received controlled ventilation and standard intensive care. From 66 to 90 hours postinjury, the extubated dogs were evaluated as to functional outcome. Morphological brain damage was evaluated at 90 hours or earlier if brain death occurred. Eight dogs in a control group were maintained at a body of temperature of 38 degrees C. Eight treated dogs had core body temperature reduced by surface cooling starting 15 minutes after balloon inflation, first to 31 degrees C for 5 hours and then to 35 degrees C from 5 to 62 hours after insult. Intraventricular pressure increased to 20 mm Hg or greater in the control group at a mean of 2.9 hours (range 2 to 4 hours) following the insult, and in the hypothermic group at a mean of 14.8 hours (range 5 to 30 hours)--that is, during the time period when the body temperature was 35 degrees C, not 31 degrees C (p = 0.01). There was no difference in peak pressures between the two groups. Brain death occurred in four of the eight dogs in the normothermic group at 18, 24, 24, and 48 hours (mean +/- standard deviation 28 +/- 13 hours) and in three of the eight in the hypothermic group at 27, 42, and 45 hours (mean 38 +/- 10 hours) (not significant). The animals surviving 90 hours (four in the normothermic and five in the hypothermic group) were neurologically near normal. The total mean macroscopically damaged brain volume was 2584 +/- 1890 cu mm in the normothermic versus 765 +/- 611 cu mm in the hypothermic group (p = 0.03). The mean necrotic volume was 741 +/- 599 cu mm in the normothermic versus 263 +/- 346 cu mm in the hypothermic group (p = 0.07). Microscopically, the damaged regions consisted of ischemic neurons, reactive glia, edema, vascular endothelial hypertrophy, and erythrocyte extravasation. It is concluded that, in this model, immediate postinsult hypothermia of 31 degrees C (not 35 degrees C) for 5 hours prevents a rise in IVP and significantly decreases cerebral tissue damage, but does not prevent brain herniation during rewarming.

Wound botulism in a patient with a tooth abscess: case report and review

We describe a case of wound botulism associated with a tooth abscess in a 5-year-old boy. We reviewed the literature and reports to the Centers for Disease Control and Prevention (Atlanta) of laboratory-confirmed cases of wound botulism. From 1943 through 1990, 47 cases were reported. Type A botulinus toxin was identified in 32 cases, type B in 13, types A and B in 1, and an unknown type in 1. Botulism was associated with wounds from trauma, use of injectable drugs, and surgery. Sinusitis after use of intranasal cocaine has also been associated with botulism. Treatment for wound botulism includes prompt debridement of the wound for eliminating anaerobic conditions, intensive care, and treatment with antitoxin.

Evaluation of a low-temperature calcium phosphate particulate implant material: physical-chemical properties and in vivo bone response

A study was conducted to evaluate the osteoconductive ability of a particulate, low-temperature hydroxylapatite (HA(LT)) material (OsteoGen; Impladent, Holliswood, NY). An implantable chamber model was used to determine the ability of this material to encourage bone ingrowth into channels lined with either rough-surfaced titanium or rough-surfaced plasma-sprayed hydroxylapatite. The HA(LT) material increased bone ingrowth into the titanium-lined channels comparable with that in plasma-sprayed hydroxylapatite-coated channels. It was incorporated into ingrowing bone without intervening soft tissue, with the bone bonding directly to the material surface in much the same fashion as it bonds at the plasma-sprayed hydroxylapatite surface. Mechanical testing of the ingrown bone showed no weakness because particles were incorporated. At 12 weeks, the particles began to show signs of dissolution. It was concluded that the HA(LT) material is a biocompatible, osteoconductive material that conducts bone ingrowth in much the same way as high-temperature particulate hydroxylapatite ceramics. This material has the additional desirable property of being slowly resorbable, a beneficial characteristic for many bone-filling applications.

Altering the antigenicity of proteins

To better understand the binding interaction between antigen and antibody we need to distinguish protein residues critical to the binding energy and mechanism from residues merely localized in the interface. By analyzing the binding of monoclonal antibodies to recombinant wild-type and mutant myohemerythrin (MHr) proteins, we were able to test the role of individual critical residues at the highly antigenic site MHr-(79-84), within the context of the folded protein. The results directly show the existence of antigenically critical residues, whose mutations significantly reduce antibody binding to the folded protein, thus verifying peptide-based assignments of these critical residues and demonstrating the ability of buried side chains to influence antigenicity. Taken together, these results (i) distinguish the antigenic surface from the solvent-exposed protein surface before binding, (ii) support a two-stage interaction mechanism allowing inducible changes in protein antigens by antibody binding, and (iii) show that protein antigenicity can be significantly reduced by alteration of single critical residues without destroying biological activity.

Who eats what? A comparison of dietary patterns among men and women in different occupational groups

Dietary data were obtained during a community-based study of risk factors for heart disease in 1983. Results were compared for men and women in broadly defined socioeconomic groups based on occupation and education. People in higher status occupation groups and with more education, and women more than men, had food consumption patterns more consistent with current health promotion messages. For example, they reported eating more wholemeal or brown bread and more fresh fruit and vegetables, drinking more skim or low-fat milk, eating fewer eggs and having less sugar in hot drinks or on cereals. There was some evidence, however, of an interplay of influences of cost and health awareness. For example, retired men were less likely than employed men to eat butter, cream, fresh fruit and vegetables, while men in the upper socioeconomic groups reported relatively higher consumption of butter and cream. The results emphasise the need for a range of strategies aimed at specific subgroups in order to improve national dietary patterns in Australia.

Does the occupational structure of the Hunter Region explain the high rates of ischaemic heart disease among its men?

To compare rates of ischaemic heart disease (IHD) among men in occupation groups defined by the new Australian Standard Classification of Occupations (ASCO) and to investigate whether their high mortality rates from IHD in the Hunter Region of New South Wales (NSW) could be explained by its occupational structure, we used official death records and data from the World Health Organization MONICA Project conducted in Newcastle. The study population consisted of men aged 25 to 64 years in NSW and in the Hunter Region for whom occupational information was available. For deaths from IHD between 1984 and 1988 in NSW, indirectly standardised mortality and morbidity ratios (SMRs) were: significantly low for professionals, 66 (95% confidence interval (CI) 60-71) and managers and administrators, 79 (95% CI 74-83); intermediate for paraprofessionals (92), clerks (94) and salesmen and personal service workers (97); and significantly high for tradesmen, 113 (95% CI 107-118), labourers and related workers, 118 (95% CI 113-124) and plant and machine operators and drivers, 125 (95% CI 118-133). Broadly similar patterns were found for IHD deaths and for fatal and nonfatal myocardial infarction in the Hunter Region. When occupation- and age-specific mortality rates from IHD were used to calculate SMRs for the Hunter Region, SMRs for all ASCO groups except paraprofessionals were over 100. Mortality rates for occupational groups classified by ASCO were consistent with well-established differences associated with socioeconomic status.(ABSTRACT TRUNCATED AT 250 WORDS)

Monkey model of severe volume-controlled hemorrhagic shock with resuscitation to outcome

Seventeen cynomolgus monkeys under N2O analgesia and sedation were subjected to severe volume-controlled hemorrhagic shock (shed blood volume of 21 or 27 ml/kg). In 12 monkeys, resuscitation was started after increasing periods of hemorrhagic shock from 30 min to 5 h. In five additional monkeys, volume-controlled hemorrhage was modified at hemorrhagic shock 30 min to control MAP at 30 mmHg: resuscitation was started at hemorrhagic shock of 2 h. A clinically relevant resuscitation protocol consisted of a field phase from 0 to 6 h (lactated Ringer's solution, spontaneous breathing), and a hospital intensive care phase from 6 h to 48 h (blood, lactated Ringer's solution to mean arterial pressure (MAP) greater than or equal to 70 mmHg, controlled ventilation, advanced life support). Fifteen of the 17 monkeys survived. After outcome evaluation at 4 or 7 days, the eight monkeys with "moderate insult" had only transient functional impairment. Of the nine with "severe insult," three showed signs of moderate transient non-oliguric renal failure. Eight of the 12 monkeys studied morphologically showed scattered liver cell damage. None of the monkeys developed pulmonary dysfunction or functional or morphologic evidence of cerebral damage. This study establishes a new hemorrhagic shock-resuscitation model simulating field-to-hospital life support. Severe hemorrhagic shock with MAP 30-40 mmHg for 90-120 min (without trauma or sepsis) can lead to complete functional recovery after transient malfunction of liver and kidneys.

Microcapsules through polymer complexation. II. By complex coacervation of polymers containing a low charge density

Relationships between ionizable group content, structure and molecular weight, solubility and solution behaviour, and the efficacy of ionic complex formation through complex coacervation, have been established for a range of sparingly soluble synthetic weak polyelectrolyte polymers with low charge content, based on hydroxyalkyl methacrylates. Selected polymers containing methacrylic acid (acidic) and dimethylaminoethyl methacrylate (basic) functionality show promise as capsule-forming pairs for the entrapment of mammalian cells. The solubility of basic polymers and their ability to form microcapsules with structural integrity is enhanced through quaternization of the N-methyl functionality to the quaternary ammonium group. The survival of guinea-pig erythrocytes encapsulated for 4 d in this promising system was shown by the Drabkin's test to be about 41% of the control sample.

Comparison of bovine collagen xenografts to autografts in the rabbit

The use of bovine tendon as a xenograft material in humans is attractive because of its ready availability and favorable mechanical characteristics. Previous research has shown that the fibroblasts and some extracellular proteoglycans and glycoproteins, not the collagen matrix itself, in bovine tendon are primarily responsible for its antigenicity. Various attempts have been made to decrease the antigenicity of these grafts. A chloroform/methanol (CM) extraction procedure has been developed that selectively removes the fibroblasts from bovine tendon without destroying the collagen matrix. The mechanical, immunologic, and local host tissue responses to these grafts were compared to autografts and to untreated and glutaraldehyde-treated bovine tendon xenografts. The humoral immune response to a purified bovine Type I collagen product was also studied. The central two-thirds of a rabbit Achilles tendon were replaced with a reversed autograft or an experimental graft. Histologic examination of one- and two- week specimens showed an acute inflammatory response to all grafts. Untreated grafts stimulated a severe inflammatory response and were almost completely resorbed by two weeks. Glutaraldehyde-treated grafts were encapsulated. Cellular repopulation was minimal and inflammatory response was more persistent than in the autograft and CM groups. Inflammatory response to CM-treated grafts was similar to that of autografts. The CM grafts repopulated rapidly with host cells. The mechanical strength of CM grafts was equal to autograft controls at 12 weeks. The mechanical strength of untreated and glutaraldehyde-treated grafts was significantly lower. Measurement of the humoral immune response to these grafts was conducted in an independent group of animals using an enzyme-linked immunosorbent assay. A significant antibody response to untreated, glutaraldehyde-fixed, and CM-treated grafts was detected at 30 days. Antibody titers to glutaraldehyde-fixed and untreated grafts remained elevated at 60 and 90 days. In the CM group, antibody titers decreased to the level of autograft controls by 90 days. No significant antibody response was detected toward purified bovine Type I collagen.

In vitro tendon cell growth rates on a synthetic fiber scaffold material and on standard culture plates

Growth rates of rat tendon fibroblasts cultured in a three-dimensional carbon fiber matrix were compared with those of cells cultured on standard flat culture plates. The carbon fiber has been used as a tissue scaffold for tendon and ligament repair in animal and clinical studies. While cell growth on the culture plates appears to follow a growth curve containing a lag phase, a log phase, and plateau phase of growth, cell growth in the fiber matrix was characterized by a suppressed log phase of growth. SEM and cytotoxicity studies indicated that this effect was not caused by growth-inhibiting or cytotoxic substances from the carbon fiber. While we cannot rule out the possibility that cell growth was influenced by the surface chemistry of the carbon substrate, evidence from this and other studies suggests that the observed effect was caused by a lack of readily available surface area for cell attachment and growth on the small fibers. Because cell colonies growing on individual fibers are limited (at least in theory) to growing in two directions only, they enjoy limited opportunities for cell migration and growth--in contrast with cell colonies on flat culture plates. These results suggest fundamental differences in the mechanisms controlling cell growth on planar vs. three-dimensional fiber substrates.

Synthesis and characterization of a recombinant myohemerythrin protein encoded by a synthetic gene

The antigenic epitopes of the myohemerythrin (MHr) molecule have been studied extensively. The critical amino acid residues responsible for its immune recognition have been identified by using synthetic peptides and the technique of epitope scanning. To assess the true relevance of these techniques for determining the molecular mechanism of antigenic recognition and immunogenicity, the results obtained with isolated peptides should be tested in the context of the folded protein. To this end, we have designed and constructed a synthetic MHr gene, in modular form, which will allow subsequent alterations of nucleotide sequence encoding epitopes of interest. We have produced the recombinant protein at high level, and have shown by several criteria that it possesses the chemical, physical and immunological properties of the native worm protein. Thus, we have developed a valuable system for detailed immunological studies of the structure and chemistry required for antibody binding to protein.

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.

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.