Blood culturing practices in a trauma intensive care unit: does concurrent antibiotic use make a difference?

BACKGROUND

Febrile trauma patients have repeated blood cultures drawn during a prolonged hospitalization. We examined the diagnostic yield of blood cultures in severely injured patients to determine whether concurrent antimicrobial therapy or prophylactic administration of antibiotics affects blood culture growth. We also determined how rapidly growth changed to determine whether total numbers of blood cultures could be decreased. The hypotheses of the study were that concurrent antimicrobial administration affects blood culture yield, prophylactic administration alters the culture result, and repetitive culturing is unnecessary.

METHODS

A retrospective chart review of trauma patients with minimum Injury Severity Score of 15 and minimum 5-day intensive care unit length of stay was performed. The dates and results of blood cultures and antibiotic type and administration dates were recorded. "Prophylactic" antibiotics were defined as antibiotics administered on admission to the unit. Computer software was used to match the blood culture date to the period of antimicrobial administration. Categorical data were compared using Fisher's exact test.

RESULTS

Two hundred fifty-eight patients met entry criteria, and 208 charts were complete for review. One hundred twenty-nine patients had 347 sets of blood cultures drawn. The positive blood culture rate was 10.8% in patients off antibiotics, and 13.9% in patients on antibiotics (p = 0.68). All prophylactic antibiotics included a beta-lactam. Only 18% of positive blood cultures in patients receiving prophylactic antibiotics were sensitive to beta-lactams as opposed to 59% sensitivity in those who did not receive prophylaxis (p = 0.03). One hundred seventy-six sets of blood cultures were performed after an initial positive culture. Only three patients with an initial positive culture had a second positive culture with a different organism. The mean time to culturing a new organism after initial growth was 19 days.

CONCLUSION

Concurrent antimicrobial administration does not alter blood culture yield. Prophylactic administration alters the type of organism cultured. Little new information is gained from repetitive culturing.

Nonoperative management of blunt splenic injuries: factors influencing success in age >55 years

Historically poor success rates of nonoperative management of splenic injuries in elderly patients have led to recommendations for operative intervention in patients more than 55 years of age. Recent studies are in opposition to earlier recommendations revealing equal success rates of nonoperative management of splenic injuries in all age groups. A retrospective chart review was performed to assess factors related to the successful management of splenic injuries in patients over 55 years of age at a Level I trauma center. Thirty-seven patients over 55 presented with blunt splenic injuries during the 5-year study period. Thirteen patients were taken immediately to the operating room on the basis of clinical findings and/or abdomen/pelvis CT results. Nonoperative management was attempted in 24 patients on the basis of CT findings. Nonoperative management was successful in 15 patients (62.5%) and failed in eight patients (33.3%). Patients who failed nonoperative management had significantly higher American Association for the Surgery of Trauma splenic injury grade and associated pelvic free fluid. There were no deaths related to complications from failed nonoperative management. We conclude that nonoperative management of blunt splenic injuries in patients over 55 may be attempted. Patients with higher-grade injuries and pelvic free fluid are at greater risk for failure. Patients with these two findings must be monitored closely. The physicians caring for elderly patients with high-grade splenic injuries and free fluid in the pelvis must use clinical judgment regarding the need and timing of operative management.

Nonoperative Management of Blunt Splenic Injuries: Factors Influencing Success in Age <55 Years

Historically poor success rates of nonoperative management of splenic injuries in elderly patients have led to recommendations for operative intervention in patients more than 55 years of age. Recent studies are in opposition to earlier recommendations revealing equal success rates of nonoperative management of splenic injuries in all age groups. A retrospective chart review was performed to assess factors related to the successful management of splenic injuries in patients over 55 years of age at a Level I trauma center. Thirty-seven patients over 55 presented with blunt splenic injuries during the 5-year study period. Thirteen patients were taken immediately to the operating room on the basis of clinical findings and/or abdomen/pelvis CT results. Nonoperative management was attempted in 24 patients on the basis of CT findings. Nonoperative management was successful in 15 patients (62.5%) and failed in eight patients (33.3%). Patients who failed nonoperative management had significantly higher American Association for the Surgery of Trauma splenic injury grade and associated pelvic free fluid. There were no deaths related to complications from failed nonoperative management. We conclude that nonoperative management of blunt splenic injuries in patients over 55 may be attempted. Patients with higher-grade injuries and pelvic free fluid are at greater risk for failure. Patients with these two findings must be monitored closely. The physicians caring for elderly patients with high-grade splenic injuries and free fluid in the pelvis must use clinical judgment regarding the need and timing of operative management.

Percutaneous Removal of Spilled Gallstones in a Subhepatic Abscess

Abscess formation from spilled gallstones after laparoscopic cholecystectomy is infrequent. However, if an abscess does form and contains the spilled stones simple percutaneous drainage will not resolve the dilemma of a recurrent abscess. Open drainage has previously been recommended to remove the retained stones and decrease recurrent abscess formation. We report two cases in which the retained stones within an abscess were successfully removed using a percutaneous minimally invasive urological technique.

Percutaneous removal of spilled gallstones in a subhepatic abscess

Abscess formation from spilled gallstones after laparoscopic cholecystectomy is infrequent. However, if an abscess does form and contains the spilled stones simple percutaneous drainage will not resolve the dilemma of a recurrent abscess. Open drainage has previously been recommended to remove the retained stones and decrease recurrent abscess formation. We report two cases in which the retained stones within an abscess were successfully removed using a percutaneous minimally invasive urological technique.

Intoxicated motor vehicle passengers warrant screening and treatment similar to intoxicated drivers

BACKGROUND

Alcohol interventions decrease alcohol consumption and recurrent injury. The study hypotheses are (1) intoxicated passengers are similar to intoxicated drivers in crashes and driving under the influence of alcohol (DUI), and (2) DUI conviction rates after injury are low.

METHODS

Intoxicated motor vehicle occupants hospitalized for injury in 1996-1998 were matched to the state traffic database for crashes and DUI. Drivers and passengers were compared for crashes and DUI in the 2 years preceding and 1 year after admission. Driver DUI citation at the time of admission was also recorded. A logistic regression model for crash and DUI probability was constructed.

RESULTS

Six hundred seventy-four patients met inclusion criteria. In the 2 years preceding admission, passengers and drivers were equally cited for crashes (14.7% vs 19.3%, p = 0.12). In 1 year after admission, they were also equally cited (7.1% vs 7.7%, p = 0.92). Driver/passenger status was not a predictor by logistic regression; 13.4% of intoxicated drivers were convicted of DUI for the admitting crash.

CONCLUSION

Intoxicated passengers and drivers are equally likely to be cited for crashes and DUI before and after admission for injury. Few admitted intoxicated drivers are convicted of DUI. Screening and intervention for all intoxicated crash occupants is warranted.

Gastrointestinal persorption and tissue distribution of differently sized colloidal gold nanoparticles

The gastrointestinal uptake of micro- and nanoparticles has been the subject of recent efforts to develop effective carriers that enhance the oral uptake of drugs and vaccines. Here, we used correlative instrumental neutron activation analysis and electron microscopy to quantitatively and qualitatively study the gastrointestinal uptake and subsequent tissue/organ distribution of 4, 10, 28, and 58 nm diameter metallic colloidal gold particles following oral administration to mice. In our quantitative studies we found that colloidal gold uptake is dependent on particle size: smaller particles cross the gastrointestinal tract more readily. Electron microscopic studies showed that particle uptake occurred in the small intestine by persorption through single, degrading enterocytes in the process of being extruded from a villus. To our knowledge this is the first report, at the ultrastructural level, of gastrointestinal uptake of particulates by persorption through holes created by extruding enterocytes.

Evaluation of cervical spine in intensive care patients following blunt trauma

The aim of this study was to review a Level 1 trauma center's use of early (< 72 hours from injury) limited MRI to "clear" cervical spine extradural soft tissue injuries in ICU patients sustaining blunt trauma. A retrospective review of the records of patients meeting entry criteria during 1997 was performed. Demographic data, cervical spine radiographic and imaging evaluation, results, and follow-up information were gathered. One hundred and fifty patients met criteria. Forty-one patients had initial static radiographs that revealed cervical spine trauma. Twenty-seven of the 108 patients with normal initial static radiographs had evidence of extradural soft tissue injury on MRI indicating potential spinal column instability. Twenty-one of the 108 patients had negative MRI and were liberated from cervical spine precautions at a mean of 2.9 +/- 0.9 days from injury. The remaining patients were cleared of cervical spine precautions by plain radiographs and reliable clinical examinations, or by dynamic radiographs, or they died before complete evaluation. The diagnosis of acute injury to the cervical spine from blunt trauma in ICU patients must include evaluation of the osseous spine and extradural soft tissues. Dynamic studies such as flexion and extension views place the obtunded ICU patient at risk of potential neurologic injury. MRI is a noninvasive imaging technique that allows evaluation of extradural soft tissue injury with potentially less patient risk and with fewer personnel. MRI allows early liberation of cervical spine precautions in those patients with negative studies. Further studies are needed to compare specific ligamentous injury patterns by MRI with dynamic studies of the C-spine to further define MRI injury patterns indicating risk of acute spinal instability.

Assembly of a fibronectin matrix by adherent platelets stimulated by lysophosphatidic acid and other agonists

Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are agonists of the endothelial differentiation gene (Edg) family of G-protein-coupled receptors. LPA and S1P are generated by platelet activation during blood coagulation. Both lipids induce assembly of exogenous fibronectin (FN) by fibroblasts. This study examined whether LPA and S1P stimulate binding and assembly of fluoresceinated FN (FITC-FN) by adherent platelets. LPA enhanced deposition of FITC-FN into linear arrays overlying platelet surfaces and on edges of platelets adherent to FN or vitronectin (VN). Deposition was greater when platelets were adherent to FN than to VN and was elicited by platelet agonists with the following order of potency: thrombin > LPA = ADP (adenosine diphosphate) > S1P. The linear pattern of FITC-FN deposition was different from the more diffuse pattern of Alexa-fibrinogen (Alexa-FGN) binding to adherent platelets. FITC-FN was deposited by adherent platelets that had dense arrays of cytoskeletal actin when stained with rhodamine-phalloidin. The 70-kd N-terminal fragment of FN or L8 monoclonal antibody to a self-association domain of FN abolished deposition of FITC-FN but had no effect on binding of Alexa-FGN. Conversely, integrilin did not attenuate deposition of FITC-FN but abolished binding of Alexa-FGN. RGDS (Arg-Gly-Asp-Ser) or antibodies to alpha5beta1 or alphaIIbbeta3 integrins caused a partial decrease in LPA-induced deposition of FITC-FN. Correlative electron microscopy with anti-FITC coupled to gold beads revealed linear arrays on platelet surfaces associated with less than 20-nm-diameter filaments. These observations demonstrate that LPA, thrombin, ADP, and S1P induce adherent platelets to bind and assemble FN and suggest that platelets may contribute to early deposition of FN matrix after vascular injury.

Diphosphoryl lipid A from Rhodobacter sphaeroides blocks the binding and internalization of lipopolysaccharide in RAW 264.7 cells

Diphosphoryl lipid A derived from the nontoxic LPS of Rhodobacter sphaeroides (RsDPLA) has been shown to be a powerful LPS antagonist in both human and murine cell lines. In addition, RsDPLA also can protect mice against the lethal effects of toxic LPS. In this study, we complexed both the deep rough LPS from Escherichia coli D31 m4 (ReLPS) and RsDPLA with 5- and 30-nm colloidal gold and compared their binding to the RAW 264.7 cell line by electron microscopy. Both ReLPS and RsDPLA bound to the cells with the following observations. First, binding studies revealed that pretreatment with RsDPLA completely blocked the binding and thus internalization of ReLPS-gold conjugates to these cells at both 37 degrees C and 4 degrees C. Second, ReLPS was internalized via micropinocytosis (noncoated plasma membrane invaginations) involving formation of caveolae-like structures and leading to the formation of micropinocytotic vesicles, macropinocytosis (or phagocytosis), formation of clathrin-coated pits (receptor mediated), and penetration through plasma membrane into cytoplasm. Third, in contrast, RsDPLA was internalized predominantly via macropinocytosis. These studies show for the first time that RsDPLA blocks the binding and thus internalization of LPS as observed by scanning and transmission electron microscopy.

Retrospective Study of Neostigmine for the Treatment of Acute Colonic Pseudo-Obstruction

Acute colonic pseudo-obstruction (ACPO) typically develops postoperatively or after severe illness. Studies suggest that pharmacologic manipulation with intravenous (IV) neostigmine (NSM) may be an effective and less invasive treatment modality for ACPO with minimal side effects. The purpose of this study was to retrospectively assess the efficacy and incidence of complications of an IV NSM bolus in patients with ACPO. Eight patients with ten episodes of ACPO were treated with a bolus dose of NSM. Rapid and effective decompression of the colon was achieved in six episodes after a single dose of NSM at a mean of 22.8 ± 13.5 minutes. In three episodes decompression occurred after a second dose of NSM at a mean of 44.7 ± 37.7 minutes. One patient failed NSM treatment but responded to a Cystografin enema. One patient experienced significant bradycardia. NSM is a simple, safe, and effective treatment for ACPO and based on result comparison of this study and previous studies both bolus and slow infusion dosing practices of NSM are effective. The NSM bolus dosing side effect profile has been shown to include significant bradycardia, whereas when NSM was infused over one hour significant bradycardic episodes requiring treatment have not been encountered. We propose that a prospective study evaluating NSM dosing as an IV bolus versus an IV infusion would be useful in determining whether NSM infusion can be proven safer than bolus dosing for the treatment of ACPO.

Retrospective study of neostigmine for the treatment of acute colonic pseudo-obstruction

Acute colonic pseudo-obstruction (ACPO) typically develops postoperatively or after severe illness. Studies suggest that pharmacologic manipulation with intravenous (i.v.) neostigmine (NSM) may be an effective and less invasive treatment modality for ACPO with minimal side effects. The purpose of this study was to retrospectively assess the efficacy and incidence of complications of an i.v. NSM bolus in patients with ACPO. Eight patients with ten episodes of ACPO were treated with a bolus dose of NSM. Rapid and effective decompression of the colon was achieved in six episodes after a single dose of NSM at a mean of 22.8 +/- 13.5 minutes. In three episodes decompression occurred after a second dose of NSM at a mean of 44.7 +/- 37.7 minutes. One patient failed NSM treatment but responded to a Cystografin enema. One patient experienced significant bradycardia. NSM is a simple, safe, and effective treatment for ACPO and based on result comparison of this study and previous studies both bolus and slow infusion dosing practices of NSM are effective. The NSM bolus dosing side effect profile has been shown to include significant bradycardia, whereas when NSM was infused over one hour significant bradycardic episodes requiring treatment have not been encountered. We propose that a prospective study evaluating NSM dosing as an i.v. bolus versus an i.v. infusion would be useful in determining whether NSM infusion can be proven safer than bolus dosing for the treatment of ACPO.

Coexisting dysfibrinogenemia (gammaR275C) and factor V Leiden deficiency associated with thromboembolic disease (fibrinogen Cedar Rapids)

Fibrinogen Cedar Rapids is a heterozygous dysfibrinogenemia (gammaR275C) that was associated with thromboembolism during and following pregnancy in three second-generation family members who also were heterozygotic for factor V Leiden (V R506Q). Like other dysfibrinogenemias with substitutions at position 275 of the gamma-chain, fibrinogen Cedar Rapids is characterized by defective end-to-end intermolecular fibrinogen and fibrin 'D : D' associations, a fibrin network structure that is composed of thicker and more highly branched fibers, normal fibrin 'D: E' associations, and normal factor XIII-mediated crosslinking of fibrinogen and fibrin. In addition, Cedar Rapids fibrinogen and fibrin displayed delayed plasmin lysis rates. Compared with normal fibrinogen, platelet aggregation or platelet fibrinogen receptor clustering was defective in the presence of fibrinogen Cedar Rapids. Most subjects with gammaR275 mutations do not experience clinical thrombotic disorders, suggesting that the combination of a factor V Leiden defect and a gammaR275C dysfibrinogenemia predisposes to thromboembolic disease.

An evaluation of two methods for chronic central venous access device placement

BACKGROUND

Chronic venous access devices (CVADs), placed for phlebotomy and the administration of medications and nutrition, require fluoroscopy to confirm correct catheter position. Long-term central venous catheters placed using an electromagnetic catheter locating system (EMCLS) could result in decreased radiation exposure and decreased cost without compromising accuracy of position.

METHODS

Charts of patients who underwent placement of CVADs at University of New Mexico (UNM) Hospital or UNM Cancer Center were reviewed. Inclusion criteria included age >20 years and placement of a central CVAD utilizing fluoroscopy (group 1) or the EMCLS (group 2). Radiation exposure, complications, cost, and accuracy of placement were determined for each technique.

RESULTS

Between June 1996 and June 1998, 196 patients underwent placement of CVADs. Complete data sets were available for 46 patients in each group. There were no statistically significant differences in age, gender, complications, or operating room times (P = 0.26). Fluoroscopy and EMCLS were equally accurate for the correct placement of the tip of the line (P = 0.12). Mean patient radiation exposure was EMCLS, 30 mRem, and fluoroscopy, 771 mRem. EMCLS significantly decreased cost (P = 0.025) when compared with fluoroscopic assisted catheter placement.

CONCLUSIONS

The use of EMCLS for CVAD placement reduces radiation exposure and cost without compromising the accuracy of placement when compared with standard fluoroscopic-assisted placement.

Stab wounds to the back/flank in hemodynamically stable patients: evaluation using triple-contrast computed tomography

Triple-contrast computerized tomography (3CT) has been proposed as a method to detect high-risk injuries in hemodynamically stable patients with stab wounds (SWs) to the back/flank and to successfully triage patients with low-risk scans into a potentially cost-effective treatment algorithm. The purpose of this study was to retrospectively review our experience with the use of 3CT for diagnostic accuracy of SWs to the back/flank and to evaluate potential decreased length of stay (LOS) in the hospital for patients with low-risk scans and no associated injuries. Seventy-nine hemodynamically stable patients met criteria for inclusion in this review. Fifty-eight 3CTs were performed for initial evaluation, 44 low risk and 14 high risk, and 21 patients underwent mandatory laparotomy. The accuracy of 3CT was found to be 97.9 per cent. The LOS was significantly less in patients who had no associated injuries and a low-risk 3CT (16.5 hours), as compared with all other treatment groups. Hemodynamically stable patients with SWs to the back/flank may be safely triaged using 3CT. Patients with low-risk scans and no associated injuries may be discharged immediately, and those with potential delayed associated injuries should be observed for 6 to 24 hours. This strategy significantly decreases LOS in patients with low incidence of significant injury.

Stab Wounds to the Back/Flank in Hemodynamically Stable Patients: Evaluation using Triple-Contrast Computed Tomography

Triple-contrast computerized tomography OCT) has been proposed as a method to detect high-risk injuries in hemodynamically stable patients with stab wounds (SWs) to the back/flank and to successfully triage patients with low-risk scans into a potentially cost-effective treatment algorithm. The purpose of this study was to retrospectively review our experience with the use of 3CT for diagnostic accuracy of SWs to the back/flank and to evaluate potential decreased length of stay (LOS) in the hospital for patients with low-risk scans and no associated injuries. Seventy-nine hemodynamically stable patients met criteria for inclusion in this review. Fifty-eight 3CTs were performed for initial evaluation, 44 low risk and 14 high risk, and 21 patients underwent mandatory laparotomy. The accuracy of 3CT was found to be 97.9 per cent. The LOS was significantly less in patients who had no associated injuries and a low-risk 3CT (16.5 hours), as compared with all other treatment groups. Hemodynamically stable patients with SWs to the back/flank may be safely triaged using 3CT. Patients with low-risk scans and no associated injuries may be discharged immediately, and those with potential delayed associated injuries should be observed for 6 to 24 hours. This strategy significantly decreases LOS in patients with low incidence of significant injury.

A prospective evaluation of video-assisted thoracic surgery for persistent air leak due to trauma

BACKGROUND

The time required for air leak resolution after chest trauma is not well described. Based on an institutional review of posttraumatic air leaks our hypothesis was that video-assisted thoracic surgery (VATS) for persistent posttraumatic air leak would decrease chest tube days and length of stay compared with nonoperative management.

METHODS

Patients were offered VATS versus nonoperative management when air leaks persisted longer than 3 days and the patients were otherwise ready for discharge. Chest tube days and length of stay were recorded.

RESULTS

Of 223 trauma patients requiring chest tubes, 50 had persistent air leaks, 39 of whom were otherwise ready for discharge. Twenty-five chose VATS and 14 nonoperative (NOP) treatment. The mean chest tube days was 8.1 for VATS versus 11.8 for NOP (P = 0.001). Mean length of stay was 9.7 days for VATS and 16.5 days for NOP (P = 0.002).

CONCLUSIONS

In patients otherwise ready for discharge VATS reduces chest tube days and length of stay when used to treat persistent posttraumatic air leak.

In-house versus on-call attending trauma surgeons at comparable level I trauma centers: a prospective study

BACKGROUND

The purpose of this study was to prospectively compare patient outcomes based on the presence of in-house versus on-call attending trauma surgeons at comparable Level I trauma centers.

METHODS

Two designated Level I trauma centers agreed to prospectively review trauma admissions over a 6-month period, one institution with 24-hour in-house trauma attending surgeons (IH), and the other with trauma-attending surgeons taking call from home (OC) available to the hospital within 15 minutes of notification. A 6-month prospective study was conducted reviewing all trauma patients admitted to both trauma centers with an Injury Severity Score > or =16. Comparisons were made between institutions utilizing admission demographics, clinical presentation, times to clinical care, and mortality rates.

RESULTS

In comparison, OC and IH institutions were distinctly different in geographic environment, size, and number of patients admitted. As a group, IH patients were significantly older, with higher Injury Severity Scores and lower Glasgow Coma Scale scores than the OC group. In all comparisons, OC trauma attending surgeons responded to the trauma room with equal speed or more rapidly when compared with IH trauma attending surgeons. There were no other significant differences in either population in times to provision of clinical care or in clinical outcome.

CONCLUSION

The ability of the OC institution to be similar to the IH institution in its provision of clinical care and mortality rate is accomplished in an environment where trauma attending surgeons live within a 15-minute response time to the trauma center. Using a voice-paged trauma alert activation with accurate information and sufficient warning, evaluation, provision of care, and clinical outcome of the acutely injured patient can be provided equally by in-house trauma attending surgeons and trauma attending surgeons on-call from home.

Corrosion Casting in the Reproduction of the Microsurface Topography of Fibrillar Collagen

: We have used a two-step casting procedure to create replicas of fibrillar collagen. A negative replica or mold is first created using either Mercox casting resin or a prepolymerized methacrylate resin that was originally described by Murakami. In the second step, a positive replica is made from the first using a solution of polystyrene or polyurethane to coat the methacrylate cast. The resulting replica is removed from the methacrylate cast. Results indicate the highest level of spatial resolution is obtained using a modified Murakami resin for the negative cast and polystyrene for the positive replica. The 29-nm-wide repeat banding structure present on collagen fibrils could be clearly identified in both the methacrylate cast and in the polystyrene positive replica of the methacrylate cast. Thus high-resolution replicas can be obtained. Such replicas may be useful to imprint inplantable devices with biologically relevant textures to improve tissue integration or for the development of textured surfaces for the in vitro expansion of cultured cells.

Correlative Instrumental Neutron Activation Analysis, Light Microscopy, Transmission Electron Microscopy, and X-ray Microanalysis for Qualitative and Quantitative Detection of Colloidal Gold Spheres in Biological Specimens

: Colloidal gold, conjugated to ligands or antibodies, is routinely used as a label for the detection of cell structures by light (LM) and electron microscopy (EM). To date, several methods to count the number of colloidal gold labels have been employed with limited success. Instrumental neutron activation analysis (INAA), a physical method for the analysis of the elemental composition of materials, can be used to provide a quantitative index of gold accumulation in bulk specimens. Given that gold is not naturally found in biological specimens in any substantial amount and that colloidal gold and ligand conjugates can be prepared to yield uniform bead sizes, the amount of label can be calculated in bulk biological samples by INAA. Here we describe the use of INAA, LM, transmission EM, and X-ray microanalysis (EDX) in a model to determine both distribution (localization) and amount of colloidal gold at the organ, tissue, cellular, and ultrastructural levels in whole animal systems following administration. In addition, the sensitivity for gold in biological specimens by INAA is compared with that of inductively coupled plasma-mass spectrometry (ICP-MS). The correlative use of INAA, LM, TEM, and EDX can be useful, for example, in the quantitative and qualitative tracking of various labeled molecular species following administration in vivo.

Intracellular divalent cation homeostasis and developmental competence in the hamster preimplantation embryo

The intracellular magnesium and calcium ion concentrations of in vivo-developed 2-cell hamster embryos were measured using ratiometric fluorometry. Intracellular magnesium and calcium ion concentrations were found to be 0.369 +/- 0.011 mM and 129.3 +/- 7.5 nM respectively. Culture of 1-cell hamster embryos for 24 hr to the 2-cell stage in control medium containing 0.5 mM magnesium and 2.0 mM calcium resulted in approximately a threefold increase to 343.5 +/- 8.0 nM in intracellular calcium ion concentration, while magnesium ion levels were not altered (0.355 +/- 0.007 mM). Increasing medium magnesium concentrations to 2.0 mM significantly increased intracellular magnesium ion concentrations of cultured 2-cell embryos with a concomitant reduction in intracellular calcium ion concentrations. Furthermore, increasing the medium magnesium concentration to 2.0 mM significantly increased development of 1-cell embryos collected at either 3 or 9 hr post-egg activation to the morula/blastocyst and blastocyst stages. Resultant blastocysts had an increased total cell number and increased development of the inner cell mass. Most important, however, culture with 2.0 mM magnesium increased the fetal potential of cultured 1-cells twofold. Therefore, because highest rates of development were observed in a medium that resulted in reduced intracellular calcium ion concentrations, it appears that altered calcium homeostasis is associated with impaired developmental competence of 1-cell embryos in culture.

alpha IIb beta 3 redistribution triggered by receptor cross-linking

Fibrinogen binding to alpha IIb beta 3 on adherent, spread platelets triggers active, cytoskeletally-directed redistribution of fibrinogen/alpha IIb beta 3 complexes on the platelet surface. Gold-conjugated fibrinogen, unlabeled, soluble fibrinogen, and individual fibrinogen molecules have been demonstrated to trigger receptor redistribution. Here we examine the respective roles of receptor cross-linking and ligand occupancy of receptors in initiating this movement. Monovalent, alpha IIb beta 3-binding fibrinogen fragments RGDS and HHLGGAKQAGDV did not trigger receptor redistribution, suggesting that ligand binding to a single receptor is an insufficient stimulus. Binding of monoclonal antibodies 10E5, AP2, and AP3 to the receptor did not trigger receptor movement. However, cross-linking these receptor-bound monoclonal antibodies by polyclonal anti-mouse IgG or by conjugation of the anti-receptor antibody to large colloidal gold particles triggered receptor redistribution identical in rate, pattern, and final distribution to that previously seen with fibrinogen binding. We conclude that receptor cross-linking provides the signal for initiation of fibrinogen/alpha IIb beta 3 complex redistribution on platelet surfaces.

Use of gold-labeled ovalbumin to correlate antigen deposition and localization with tissue response

This study was performed to evaluate a technique for correlating the location of antigen within sensitized tissues with physiological response. Guinea pigs actively sensitized by intraperitoneal injection of ovalbumin (OVA) were euthanized, and urinary bladders were removed. Gold beads (18 nM diameter) were conjugated to OVA (OVA-Au) and bovine serum albumin (BSA-Au). Bladder tissue was suspended in tissue baths, exposed to OVA, OVA-Au, BSA, and BSA-AU, and tissue contraction and histamine release were determined. Bladder tissues were examined by electron microscopy to determine distribution of gold-labeled antigen at 1 and 5 min after exposure. Exposure of bladder tissue from sensitized guinea pigs to OVA stimulated concomitant contraction and histamine release which reached maximal levels within 3 min; bladder tissue from control, nonsensitized guinea pigs did not respond to OVA. BSA failed to stimulate response from OVA-sensitized or control bladder tissue. Labeled antigen was adhered to mucosa of sensitized bladder tissue 1 min after exposure to OVA-Au. OVA-Au was present within the mucosa and submucosa of sensitized tissues within 5 min. OVA-Au did not adhere to, or become internalized by, control tissues, and BSA-Au did not adhere to, or become internalized by, any tissues. Labeling of antigen with gold allowed the location of antigen within tissues to be determined and did not affect the response of sensitized tissues to antigen exposure.

Three-dimensional extracellular matrix textured biomaterials

Clinical and experimental investigations have reported that manufactured surface topographies have significant effects on cell adhesion and tissue integration. However, essentially all previously examined topographies bear little relation to cell adhesion substrates found in biological tissues. In vivo, many cells are adherent to extracellular matrices (ECM), which have an extremely complex 3-D topography in the micrometre to nanometre range. In addition, many studies indicate that micro- and nano-scale mechanical stresses generated by cell-matrix adhesion have significant effects on cellular phenotypic behaviour. In this report we describe methodology for the fabrication of topographic replicas of the subendothelial ECM topography with a biomedical polyurethane. Using three-dimensional high resolution scanning electron microscopy, accurate replication of subendothelial ECM topography from the macroscopic to the macromolecular scale is demonstrated. Bovine aortic endothelial cells cultured on the ECM replicas spread more rapidly and had a three-dimensional appearance and spread areas at confluence which appeared more like endothelial cells in native arteries, compared with cells cultured on untextured control surfaces. Since the fabrication process may be used with many different types of materials, including polymers of synthetic and biological origin, these biomimetic ECM-textured surfaces may find both research and clinical applications.