Biomedical subjects
Publications and source records attributed to C McCullough.
The five independent second-order elastic constants of a transversely isotropic aluminum/alumina fiber composite have been measured for the first time using a resonant ultrasound spectroscopy technique. These data were used to deduce the elastic constants and engineering moduli for off-axis loading conditions.
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beta-Defensins are microbicidal peptides implicated in host defense functions of phagocytic leukocytes and certain surface epithelial cells. Here we investigated the genetic structures and cellular expression of BNBD-4, -12, and -13, three prototypic bovine neutrophil beta-defensins. Characterization of the corresponding cDNAs indicated that BNBD-4 (41 residues) derives from a 63-amino acid prepropeptide and that BNBD-12 (38 residues) and BNBD-13 (42 residues) derive from a common 60-amino acid precursor (BNBD-12/13). The peptides were found to be encoded by two-exon genes that are closely related to bovine epithelial beta-defensin genes. BNBD-4 and BNBD-12/13 mRNAs were most abundant in bone marrow, but were expressed differentially in certain non-myeloid tissues. In situ hybridization and immunohistochemical studies demonstrated that BNBD-4 synthesis is completed early in myelopoiesis. BNBD-12 was localized exclusively to the novel dense granules, organelles that also contain precursors of cathelicidins, antimicrobial peptides that undergo proteolytic processing during phagocytosis. In contrast to cathelicidins, Western blot analyses revealed that mature beta-defensins are the predominant organellar form in myeloid cells. Stimulation of neutrophils with phorbol myristate acetate induced secretion of BNBD-12, indicating that it is co-secreted with pro-cathelicidins. The exocytosis of BNBD-12 by activated neutrophils reveals different mobilization pathways for myeloid alpha- and beta-defensins.
BACKGROUND: The outcome of orthotopic liver transplantation (OLTX) in patients retransplanted for severe hepatitis B virus (HBV) in the first allograft has been poor due to high rates of HBV reinfection and even more aggressive disease in the second graft. Recent data suggest that hepatitis B immunoglobulin (HBIg) given after transplantation can be successful in delaying or preventing HBV reinfection in patients transplanted for chronic hepatitis B cirrhosis. We report the successful retransplantation of patients who developed recurrent or de novo hepatitis B after OLTXY. METHODS: Using similar HBIg regimens, two centers retransplanted seven patients after they developed recurrent or de novo hepatitis B in the first allograft. At retransplantation all seven patients were HBs antigen (Ag) positive; four patients were positive for HBeAg and HBV DNA by immunoblot assay, two patients were negative for HBeAg and HBV DNA, and one patient was positive for HBV DNA and negative for HBeAg. All patients were either HDV Ag or anti-HDV negative. One patient was anti-HCV positive. All patients received HBIg infusions after retransplantation to maintain serum anti-HBs levels >500 IU/L indefinitely. RESULTS: After retransplantation, six of seven patients are alive (86%): all are without evidence of HBV recurrence with serum negative for HBsAg, HBeAg, and HBV DNA by immunoblot assay. Liver biopsies are normal on routine studies with immunohistochemical stains for HBcAg and HBsAg also being negative. Mean follow-up of these six patients is 40.1 months (range 21-63 months). One patient (14%) developed HBV reinfection 7 months after his second transplant, in spite of maintaining target anti-HBs levels. He maintained stable liver function with minimal evidence of clinical hepatitis B, but died 8 months later from an unrelated stroke. CONCLUSIONS: We conclude that patients with recurrent or de novo hepatitis B after OLTX can be successfully retransplanted using aggressive immunoprophylaxis to prevent HBV reinfection. The failure of HBIg therapy in one patient underscores the need for other effective adjunctive anti-HBV modalities.
We identified a Canadian-Mennonite family in which a brother and sister have hydrocephalus due to obstruction at the foramen of Monro and profound bilateral sensorineural deafness. This appears to be a unique combination of anomalies and, to our knowledge, has not been reported previously. Both parents and a brother are phenotypically normal. The parents are second cousins. Thus, on the basis of consanguinity, affected sibs of both sexes, and in the absence of evidence for intrauterine infections or other adverse perinatal events, this syndrome is likely inherited in an autosomal recessive fashion.
Eighty liver allografts were studied to determine the predictive value of intraoperative biopsies and postoperative liver function tests for the development of preservation injury (PI). Peak transaminase (aspartate transaminase [AST] and alanine transaminase [ALT]) and prothrombin time (PT) values achieved by each patient during postoperative days (POD) 1 through 7 were determined. PI in day 0 preperfusion biopsies (0Pre) (obtained immediately before implantation) and postperfusion biopsies (0Post) (obtained immediately after revascularization) was categorized by histological criteria as present or absent. PI in biopsies taken during POD 2 through 14 was histologically graded as either moderate-to-severe, mild, or absent. Of the 80 allografts, 8 were omitted because of primary nonfunction or postoperative complications. 0Pre and 0Post biopsies were available on 25 of 72 (35%) and 69 of 72 (96%) allografts, respectively. Only 2 (8%) of the 0Pre biopsies showed histological PI compared with 48 (70%) of the 0Post biopsies. Fifty-nine patients were biopsied between POD 2 through 14. Of these, 15, 28, and 16 patients developed moderate-to-severe, mild, or no evidence of PI, respectively. The presence of PI in the 0Post biopsy strongly correlated with the development of PI during POD 2 through 14 (P < .0005). Peak AST and ALT values in patients with moderate-to-severe PI on POD 2 through 14 were significantly elevated compared with those patients with either mild (P = .01 and .03) or no PI (P = .02 and .006). Because of extensive overlap in AST and ALT values between the three groups, however, transaminase values were not useful in predicting the presence or absence of PI in the individual case. The development of PI during POD 2 through 14 correlated with advanced donor age (P = .06) but was unassociated with 0Pre biopsy findings, cold ischemia time, or peak PT values. We conclude that the 0Post biopsy is a valuable tool for the prediction of subsequent PI in the early postoperative period. In contrast, 0Pre biopsy findings and peak AST and ALT values are not useful in the assessment of PI.
We present a report of a transplant recipient who lost her renal allograft from hyperacute rejection. This was secondary to a weak IgG anti-HLA class I antibody that was only reactive to donor B lymphocytes. This antibody was not detected in her pretransplant serum by the conventional complement-dependent cytotoxicity assays using donor blood lymphocytes. Pretransplant sera were analyzed retrospectively by two-color flow cytometric crossmatching (FCXM). It was difficult to determine if the recipient's serum contained an IgG antibody specific for HLA on donor B cells since IgG from control AB sera and pretransplant sera bound equally well to CD19 B cells. However, when donor lymphocytes were pretreated with pronase to digest the membrane receptor for Fc domain of IgG (Fc gamma R) on non-T-cells, control IgG in AB serum did not bind to B cells and, hence, it was easy to detect binding of IgG (in pretransplant sera) to HLA on B cells. This case underscores the importance of identifying weak anti-HLA class I antibodies reactive only to B cells. Moreover, it shows that the currently used two-color FCXM lacks the specificity to detect such antibodies.
The long-term side effects of lifelong steroid immunosuppression are well documented, therefore, steroid withdrawal (SW) if safe would clearly be of benefit. From 1987-1996, 470 kidney transplants were performed at our institution. During this time period, steroid withdrawal was offered to a select group of patients (n = 43) who were at least 1 year post transplant (27.6 +/- 12.0 months, 15-64 months), had stable graft function and had experienced only mild episodes of rejection in the postoperative period. Informed consent was obtained from all participants. Twenty-five patients were male and 18 were female. The mean age at time of transplantation was 42.4 +/- 14.1 years (17-65 years). There were 28 cadaveric renal transplants (CRT), 10 living related kidney transplants (LRT) and 5 simultaneous kidney-pancreas transplants (SPK). Maintenance immunosuppression in all patients consisted of CSA 3-5 mg/kg, and AZA 1-2 mg/kg. Twenty-nine patients (67%) have remained off steroids with good renal function for 13-59 months (38.3 +/- 11.0). Steroids were restarted in 14/43 (32%) patients 1-36 months post SW (13.3 +/- 11.0 months). Eight of these 14 patients had a rise in creatinine and biopsy proven rejection, 5 of whom responded to reinstitution of steroid immunosuppression, and have stable renal function (CR = 2.0 +/- 0.4) 41-53 months (45 +/- 4.0 months) post SW. Three (7%) patients lost their allograft. One was a SPK recipient who retained good pancreatic function and subsequently received a successful 2nd kidney transplant. The other 2 patients died awaiting retransplantation. Steroids were recommenced in 6/14 patients who did not develop rejection for inability to tolerate CSA/AZA (2), anxiety (2) or recurrent disease (2). In the majority of our patients, (93%) SW did not result in immunologic graft loss. A graft loss of 7% (3) is not significantly different from the expected graft loss in a kidney transplant recipient population over a time period of 9 years. Therefore, we feel that with careful monitoring steroid withdrawal can be safely accomplished in select patients.
Measurement of liver volume in patients with advanced liver disease is used to gauge the appropriate size of donor organs and may have prognostic value. We sought to determine the accuracy of magnetic resonance imaging (MRI) in measuring liver volume in 19 adult patients under consideration for liver transplantation. We also correlated the liver volume determination to the clinical severity of disease. Liver volume was measured at MRI by averaging the calculated volumes from coronal and transverse breath-hold T1-weighted images. These results were compared to the explanted liver volume measured by fluid displacement and the explant mass. The correlation coefficient for MRI liver volume and the explant displacement volume was 0.90. The mean liver volume for Child-Pugh class AB by MRI was 1986 +/- 568 mL (1002-2470 mL) compared to 1433 +/- 379 mL (540-1889 mL) in Child-Pugh class C patients (p = .02). We conclude that MRI offers an anatomically accurate means of determining adult liver volume in vivo. Lower mean liver volumes were observed in Child-Pugh class C patients. In addition to its ability to provide tumor screening and vascular assessment, MRI is able to provide accurate determinations of liver volume in patients undergoing liver transplant evaluations.
Currently there is a paucity of data regarding the influence of high serum triglyceride levels on cyclosporin A (CyA) levels and dosing. We therefore undertook a retrospective study to determine the relationship of serum lipid levels to CyA levels and CyA dosages. Renal transplant patients at a 0.5-to-3-year post-transplant stage, with a stable CyA dosage, who were not on medications that affect CyA metabolism or renal function, were entered into the study. The CyA dosage was adjusted by clinicians to maintain whole blood. 12-h CyA trough levels between 200 and 250 ng/ml (monoclonal TDX method, which measures the parent compound). Forty-four patients qualified for the study. The data clearly indicated that high cholesterol levels (> 300 mg/dl and with normal triglyceride levels) did not influence the CyA levels or the dosages. Conversely, high triglyceride levels ( > 500 mg/dl) significantly reduced the amount of CyA required. A decreased clearance of CyA in the presence of hypertriglyceridemia led to high CyA levels in some patients. Reducing the CyA dosage to achieve levels between 200 and 250 ng/ml improved renal allograft function and decreased other side effects attributed to CyA toxicity. These studies indicate that high triglyceride levels, but not high cholesterol levels, increase CyA levels, which can lead to CyA toxicity.
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UNLABELLED: Aggressive administration of hepatitis B immune globulin (HBIg) has been shown to prevent hepatitis B viral (HBV) infection of the allograft; however, the clinical sequela of such therapy has not been previously described. We reviewed our experience with high dose, intravenous infusion of an intramuscular HBIg preparation to assess the effectiveness and complications of such therapy. Thirty three orthotopic liver transplants (OLTx) were performed in 32 patients with chronic HBV cirrhosis at the University of Virginia between March 1990 and June 1995. Twenty-nine of 32 (91%) patients remain free of HBV recurrence (defined by undetectable serum HBsAg and HBV-DNA) after a mean of 21 months (2-54 months), with one patient requiring retransplantation. Three (10%) patients died of non-HBV causes (two vascular events, one infectious event). Twenty episodes of acute cellular rejection were treated in 18 patients (two had two episodes). Sixteen rejections occurred within 18 d of transplant, 19 by day 120, and one late rejection occurred at 18 months owing to medication non-compliance. Eighteen patients had at least one documented infection. Six patients were treated for CMV infection (five empirically). Eight patients were treated for HSV infections (seven mild herpetic labialis and one herpetic keratitis). Four patients had documented fungal infection (one mucormycosis pneumonia and three minor superficial mucosal infections). With the exception of one necrotizing pneumonia, 11 bacterial infections were successfully treated with conventional antimicrobial agents. No patient developed post-transplant lymphoproliferative disorder. Symptoms associated with HBIg infusion were intermittent but frequent and consisted of myalgias, predominantly back pain (90%), headache (20%) and flushing (5%). No patient experienced anaphylaxis, fever, rash, arthritis or hypotension. Despite the potential for mercury toxicity and HCV transmission in the HBIg formulations currently available in the United States, serum mercury levels remained below standards for industrial exposure (60 micrograms/ml), and only one individual developed post-transplant HCV infection after receiving multiple units of unscreened blood prior to 1991. SUMMARY: High-dose HBIg prevented HBV infection of the allograft in 29 of 32 patients transplanted for HBV cirrhosis with three non-HBV associated deaths. The intravenous infusion of HBIg was frequently associated with minor side effects that were safely tolerated by patients. The risk of HCV transmission and mercury toxicity are minimal, but support the need for a new intravenous formulation of HBIg. HBIg therapy successfully decreased post-OLTx HBV recurrence with no clinical events associated with immunosuppression. Patients did non experience allergic or infusion-related complications that altered or terminated therapy. Manufacturing modifications of HBIg may allow for improved patient tolerance and decreased risks.
Two-color fluorescence cytometry (FCXM) has recently been introduced to improve the detection of anti-HLA antibodies that react to donor cells, especially in recipients receiving kidney allografts. Although this assay system is highly sensitive, it lacks specificity. Between 70% and 90% of potential kidney recipients with a positive FCXM would have been denied transplant if such an assay had been used alone to detect antidonor antibodies. Lack of specificity is principally due to normal or irrelevant IgG in aggregates or immune complexes binding to Fc gamma R receptors on lymphocytes including B cells and a significant subset of T cells. To circumvent this problem, we digested Fc gamma R receptors on lymphocytes with pronase. We present data demonstrating that pronase digestion of lymphocytes does not alter HLA antigenicity. In addition, pronased lymphocytes allow one to use either single- or two-color FCXM. With single-color FCXM, one can quantitate antibody reactivity to lymphocytes via a cursor (on the fluorescence histogram) that separates lymphocytes that do not bind to antibodies. We present data demonstrating that this modification renders FCXM highly sensitive and specific. In addition, one can discriminate between IgG and IgM antibodies that react to lymphocytes.
OBJECTIVE: To determine the source of medical advice to parents and treatment administered at home for children admitted to hospital with acute gastroenteritis. METHODOLOGY: A questionnaire was completed by the parents of 231 children admitted during a 12 month period. RESULTS: The majority of children had seen their family doctor or an after-hours doctor prior to admission. Clear fluids were used for two-thirds but an oral rehydration solution (ORS) was used in only one-third of children. Medications were used for half, including antibiotics (19%), antidiarrhoeals (9%), antiemetics (7%) and paracetamol (27%). Inpatient assessment suggested that the majority of children had no or mild dehydration. CONCLUSIONS: Appropriate oral rehydration is underutilized and medications are overprescribed for the treatment of acute gastroenteritis. Family doctors continue to be the major source of advice for parents. Increased use of ORS at home may reduce hospitalization rates but attempts to change these practices should be directed at parents and family doctors.
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