Multimodality imaging of exuberant mitral annular calcification in a patient presenting with transient ischaemic attack

We report an unusual case of calcification of mitral valve annulus imaged with multiple non-invasive modalities in a patient who suffered a transient ischaemic attack, probably from thrombus overlying the mitral annular calcification. Both this mode of presentation and the imaging features of the annular calcification were relatively unusual, and the images obtained are remarkably clear and diagnostic.

Intraoperative Blood Flow Measurements in Organ Allografts Can Predict Postoperative Function

A reliable method to recognize the extent of ischemia/reperfusion injury in transplantation is needed in order to tailor the immunosuppressive scheme to the needs of a damaged organ. This study sought to assess the correlation between the total and the parenchymal blood flow into a transplanted kidney (n = 71) or liver (n = 15) shortly after revascularization with the early function of the organ after transplantation. The total blood flow in the renal artery in kidney recipients or in the hepatic artery and portal vein in liver recipients was measured by an electromagnetic flowmeter. The parenchymal blood flow (in several parts of the transplanted organ) was assessed using a laser-Doppler flowmeter. Two measurements were always taken after revascularization (5 to 60 minutes apart). Vascular resistance (VR) as calculated by the difference between the mean arterial pressure (MAP) and the central venous pressure (CVP) was correlated with immediate kidney or liver function parameters. Neither total renal blood flow (RBF) nor VR was different between the immediate function (IF) and delayed graft function (DGF) groups of kidney transplant patients. However, the cortical (parenchymal) blood flow was significantly greater in the IF than the DGF group at 5 minutes: 29.98 +/- 6.13 mL/min/100 g vs 23.56 +/- 6.46 mL/min/100 g (P < .001). The difference was even more significant at 35 minutes: 33.94 +/- 7.47 mL/min/100 g vs 15.47 +/- 3.34 mL/min/100 g (P < .0001). Among liver transplant patients, the results suggested a correlation between hepatic arterial blood flow and early graft viability and function. The most reliable predictor of early graft function was the portal blood flow, which correlated with the volume of secreted bile as well as the bilirubin, and transaminase levels and coagulation profile. Further studies must confirm the value of measurements of total and parenchymal blood flow in organ transplant recipients.

Endoderm and Pancreatic Islet Lineage Differentiation from Human Embryonic Stem Cells

Human embryonic stem cells (HESCs) are a potential source of insulin-producing tissue for transplantation. Recent studies have begun to define factors that promote definitive endoderm formation from HESCs, but conditions permitting complete islet specification in vitro have not been described. Here, we study spontaneous differentiation of HESCs to definitive endoderm and pancreatic progenitor cells, and begin to determine which aspects of the protocol are required for this cell fate commitment. HESCs were differentiated in culture for up to 10 weeks, including an embryoid body (EB) formation step. Modifications to the protocol included elimination of the EB phase, varying initial cell cluster size when forming EBs, and addition of mesoderm-derived cells to EBs. Differentiated cells were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. HESCs are capable of spontaneous differentiation to cells expressing the definitive endoderm and pancreatic progenitor markers Foxa2, Sox17, and Pdx1, and ultimately, some cells express islet endocrine hormones. This differentiation occurs to a much greater extent when an EB formation step is included. Increased expression of endoderm markers during and after EB formation also correlated strongly with the size of cell clusters used to start EBs, as well as the addition of mesoderm- derived embryonic cells. This study demonstrates that a subset of differentiated HESC progeny adopt an endoderm fate and exhibit the capacity for further pancreatic lineage specification in vitro. Basal conditions were established for examining factors that can commit HESC-derived endoderm cells to specific pancreatic lineages.

Comparison of PRA-STAT, sHLA-EIA, and anti-human globulin-panel reactive antibody to identify alloreactivity in pretransplantation sera of heart transplant recipients: correlation to rejection and posttransplantation coronary artery disease

BACKGROUND

Screening pretransplantation recipient sera for percent panel reactive antibodies (%PRA) by an anti-human globulin (AHG) assay may identify recipients who are at risk for graft rejection or development of posttransplantation coronary artery disease. However, the pretransplantation AHG-%PRA does not always correlate with the occurrence of graft rejection or coronary artery disease.

METHODS

We compared the predictive capacity of the AHG-%PRA with that of an enzyme-linked immunoassay (EIA)-based PRA assay that identifies immunoglobulin G bound to soluble human leukocyte antigen (sHLA) class I molecules from pooled platelets of 240 random donors (sHLA-EIA), and that of an EIA-based assay that detects immunoglobulin G anti-HLA class I antibodies bound to sHLA derived from individual HLA-typed cell cultures (PRA-STAT). The pretransplantation sera from 130 cardiac allograft recipients were comparatively tested and results evaluated.

RESULTS

Although AHG-%PRA- and sHLA-EIA-determined PRA results were comparable, neither assay discriminated potential recipients at risk for rejection or coronary artery disease. However, cardiac allograft recipients with pretransplantation PRA-STAT sera > 10% were at risk for (1) graft rejection (77% vs 56%, p < .05); (2) more rejections/recipient (1.9 vs 1.0, p < .02); (3) graft rejection within 30 days (92% vs 38%, p < .001); or (4) development of coronary artery disease (48% vs 23%, p < .05) than recipients with pretransplantation PRA-STAT sera < 10%.

CONCLUSIONS

PRA-STAT analysis of pretransplantation sera from potential cardiac allograft recipients may be more clinically informative about HLA alloimmunity and a better predictor of adverse clinical events than either AHG-%PRA- or sHLA-EIA-determined PRA.

Augmented enterocystoplasty for neurogenic bladder associated with renal transplantation: appearance on Tc-99m MAG3 renal transplant scan

Enterocystoplasty (bladder augmentation) is a method of increasing bladder capacity in patients with small or neurogenic bladders in order to prevent vesicoureteral reflux. In patients with poorly compliant bladders, enterocystoplasty, which consists of a segment of detubularized small bowel or a portion of the stomach attached to the bladder, often helps to reduce the intravesicular pressures, thus reducing the likelihood of infection. It is also useful in treating bladder dysfunction in children with end-stage renal disease who require renal transplantation. Radiographic evaluation of patients with a renal transplant and augmented bladder often can be confusing, and may suggest a urine leak or hematoma. We report a patient with a renal transplant, bladder augmentation, and rising serum creatinine who underwent renal scintigraphy and ultrasonography.

Forces, moments, and accelerations acting on an unrestrained dummy during simulations of three wheelchair accidents

To determine the magnitude and distribution of the forces, moments, and accelerations acting on an individual sitting in a wheelchair during three possible accidents occurring while negotiating a sidewalk curb, experimental trials were performed in a bioengineering laboratory using a 50th percentile Hybrid III dummy seated in a standard wheelchair. A ramp was designed with an adjustable incline to allow the wheelchair to reach the edge of a sidewalk height platform at the desired forward speed of 2.5 miles per hour (comfortable walking speed). The wheelchair velocity was monitored via an optical pickup. Three types of accidents were simulated: (1) a wheelchair hitting straight into a curb; (2) a wheelchair falling forward straight off a curb; (3) a wheelchair falling diagonally off a curb. Each experiment was repeated three times. Each run was photographed using high-speed cameras and videotaped from three perspectives: frontal, lateral, and overhead. The results were averaged and compared with published injury Assessment Values (IAV) and Head Injury Criteria (HIC). Of significance were the following results. In the straight into a curb experiments, the wheelchair remained upright and the dummy seated. Low magnitude forces (23-73 N), moments (1-12 Nm), and accelerations (0.2-1 G) were recorded at the neck and head. The HIC was low at 0.3. These results were of no clinical significance. In the straight off a curb experiments, properly attached footrests prevented the wheelchair from toppling over but did not prevent the dummy from falling off the wheelchair. Forces (187-4,176 N), moments (3-178 Nm), and accelerations (131-206 G) of great magnitude were recorded at the head and neck when the dummy fell off the wheelchair. These values were above IAV. The HIC was 960. In the diagonally off a curb experiments, both the wheelchair and the dummy fell sideways. High-magnitude forces (274-2,313 N), moments (4-110 Nm), and acceleration (140-236 G) were recorded in the head and neck regions. The HIC was 975. These values were close to IAV and may signify potential serious injuries.

Stability of renal allograft glomerular filtration rate associated with long-term use of cyclosporine A

Renal allograft glomerular filtration rate (GFR) was measured at 4-month intervals for up to 1 year in 43 CsA-treated patients using x-ray fluorescence determination of plasma iohexol clearance. Study patients were divided into cohorts based on time (years) after transplantation at study entry (0-1; 1-2; 2-3; and > 3 years) and entry GFR levels (20-29; 30-39; 40-49; and > or = 50 ml/min/1.73 m2). GFR at study entry was 42 +/- 2 and was comparable in CAD (n = 31) versus LRD (n = 12) allografts (42 +/- 2 and 44 +/- 4 ml/min/1.73 m2, respectively). Range of entry GFR levels was similar in each of the "time at entry" cohorts defined above. Serum creatinine concentrations of 1.5-2.5 mg% were associated with GFR levels of 20-60 ml/min/1.73 m2. Serial GFR levels obtained at 4-month intervals for 1 year (n = 34 patients) were not consistent with a pattern of progressively declining GFR occurring as a function of either time after transplantation or absolute GFR level at study entry (intraindividual coefficient of variation 10.3 +/- 1.0%). Patients in the lower quartile of "entry GFR" levels (< 34 ml/min/1.73 m2) were more likely than their counterparts to have had a history of acute rejection. Results are consistent with retrospective population studies of aggregate serum creatinine levels, indicating that long-term CsA use is not uniformly associated with accelerated loss of renal allograft function consequent to a progressive, toxic nephropathy. The data also suggest that neither absolute GFR level nor time after transplantation represent indications for routine dose reduction or conversion to AZA.

Mechanisms and amelioration of acute renal allograft failure in the cyclosporine era

The fairly wide-ranging spectrum of tactics under investigation for ameliorating acute renal allograft dysfunction caused by harvest/preservation-related ischemia, acute CsA nephrotoxicity, and acute immunologic crises reflect the fact that no single approach has emerged as universally useful for mitigating the vasomotor nephropathy produced by the combined effects of each of these vectors of vasomotor renal allograft injury. Given the clinical heterogeneity of patients and allografts, it is the author's bias that, in addition to careful donor and recipient hemodynamic management, induction immunosuppressive regimens should be individualized on the basis of allograft function in the immediate postreperfusion period (judged by rate of diuresis, intraoperative parenchymal tone, renal scan profiles, and rate of decline of serum creatinine concentration) as well as patient-specific immunologic and general medical risk factors. Promising laboratory and clinical investigations of such agents as calcium channel blockers, substances promoting intrarenal vasodilator vs. vasoconstrictor prostaglandin formation, and atriopeptins have the potential to provide clinically helpful options with regard to adjunctive therapy for ameliorating acute renal allograft dysfunction associated with INF and ACR.

Detecting immunocomplex formation in sucrose gradients by enzyme immunoassay: application in determining epitope accessibility on ribosomes

A sensitive method using enzyme immunoassay and sucrose gradient to analyze immunocomplexes of biological particles has been developed. The sensitivity and application of this method were demonstrated by that the in situ accessibility of ribosomal protein epitopes could be easily determined. We used sucrose gradients to separate the ribosome-bound and the free antibodies and traced the antibodies in the gradients by an enzyme-linked immunosorbent assay. Epitopes exposed in situ are bound by specific antibodies, which in turn are detected in sucrose gradients migrating with ribosomes. This method of detecting antibody migration is more sensitive than the conventional means of using A260nm to monitor the antibody-mediated dimerization of ribosomes. Furthermore, an epitope defined by a biotin-labeled monoclonal antibody can be analyzed in the presence of other unlabeled antibodies. Thus, the relationship of different accessible epitopes in situ can be readily examined. Versatility and sensitivity of this method should make it useful in analyzing a variety of immunocomplex systems.

Epitope mapping of monoclonal antibodies to Escherichia coli ribosomal protein S3

The antigenic structure of Escherichia coli ribosomal protein S3 has been investigated by use of monoclonal antibodies. Six S3-specific monoclonal antibodies secreted by mouse hybridomas have been identified by immunoblotting of two-dimensional ribosomal protein separation gels. By using a competitive enzyme-linked immunosorbent assay, we have divided these monoclonal antibodies into three mutual inhibition groups, members of which are directed to three distinct regions of the S3 molecule. The independence of these monoclonal antibody-defined regions was confirmed by the failure of pairs of monoclonal antibodies from two inhibition groups to block the binding of biotinylated monoclonal antibodies of the third group. To determine the regions recognized by these monoclonal antibodies, chemically cleaved S3 peptides were fractionated by gel filtration and reverse-phase high-performance liquid chromatography. The fractionated peptides were coated on plates and examined for specific interaction with monoclonal antibody by enzyme immunoassay. In this manner, two epitopes have been mapped at the ends of the S3 molecule: one, in the last 22 residues, is recognized by three monoclonal antibodies; and the second, in the first 21 residues, is defined by two monoclonal antibodies. The third S3 epitope, recognized by a single monoclonal antibody, has been localized in a central segment of about 90 residues by gel electrophoresis and immunoblotting. These epitope-mapped monoclonal antibodies are valuable probes for studying S3 structure in situ.

Epitopes of Escherichia coli ribosomal protein S13

To analyze the immunochemical structure of Escherichia coli ribosomal protein S13 and its organization in situ, we have generated and characterized 22 S13-specific monoclonal antibodies. We used a competitive enzyme-linked immunosorbent assay to divide them into groups based on their ability to inhibit binding of one another. The discovery of five groups with distinct binding properties suggested that a minimum of five distinct determinants on S13 are recognized by our monoclonal antibodies. The locations of the epitopes detected by these monoclonal antibodies have been mapped on S13 peptides. Three monoclonal antibodies bind a S13 C-terminal 34-residue segment. All the other 19 monoclonal antibodies bind a S13 N-terminal segment of about 80 residues. The binding sites of these 19 monoclonal antibodies have been further mapped to subfragments of peptides. Two monoclonal antibodies recognized S131-22; three monoclonal antibodies bound to S131-40; the binding sites of three other antibodies have been located in S1323-80, with epitopes possibly associated with residues 40-80. The remaining 11 monoclonal antibodies did not bind to these subfragments. These data provide molecular basis to the structure of S13 epitopes, whose in situ accessibility may reveal the S13 organization on the ribosome.

Cyclosporine absorption in apancreatic dogs

The plasma concentration time course of orally administered cyclosporine was studied in apancreatic dogs with established islet autografts and compared with that in normal control dogs. After oral administration of cyclosporine (20 mg/kg), blood samples were collected at 0, 1, 2, 3, 4, 6, 8, and 24 hours, and the plasma cyclosporine concentrations were measured by radioimmunoassay. The plasma level of cyclosporine increased promptly in both groups after dosing. Peak plasma concentrations ranged from 435 to 1,542 ng/ml and were attained at between 2 and 6 hours in the apancreatic dogs, and concentrations from 602 to 4,414 ng/ml were attained at between 1 and 6 hours in the control dogs. Even though there was substantial variation among animals, the plasma concentration curve of the apancreatic group was quite comparable with that of the control group. The Student's test for unpaired data failed to show any significant differences over the time course. Area under the concentration-time curves, maximum concentration, and times of peak concentration were calculated. These data demonstrated the capacity of apancreatic dogs with islet autografts to absorb cyclosporine when they are stable, nutritionally normal, and have full endocrine reconstitution.

Cyclosporin-A nephrotoxicity and acute cellular rejection in renal transplant recipients: correlation between radionuclide and histologic findings

Serial radionuclide studies using both Tc-99m DTPA (perfusion) and I-131 hippuran (tubular function) were correlated with histologic findings in 25 patients with renal transplants. These cases included 15 cases of cyclosporin-A nephrotoxicity (CsA-NT) and ten cases of acute cellular rejection that were retrospectively selected on the basis of biopsy findings and favorable clinical response to therapy specific for each of these conditions. The serial radionuclide studies enabled the correct diagnosis in 12 of 15 cases of CsA-NT and eight of ten cases of acute rejection. Posttherapy radionuclide studies, furthermore, demonstrated improvement consistent with clinical response. In all cases, the radionuclide results were available at least 24 hours before biopsy findings. These results indicate that serial radionuclide studies evaluating interval changes in both perfusion and tubular function are of significant value in the diagnosis and follow-up of CsA-NT and acute cellular rejection in transplant recipients. This initial experience suggests a sensitivity of 80%.

Early graft function

1. The average serum creatinine level during the first 20 days after transplantation was lower in HLA-identical siblings than in parental donor transplants, suggesting an early effect of histocompatibility. 2. In rather small numbers of patients, the daily average serum creatinine values were not different with HLA-DR mismatching and HLA-B,DR mismatching, but were lower in the better matched transplants for the HLA-A,B loci and the HLA-A,B,DR loci. 3. The average serum creatinine values in the first 20 days after transplantation were correlated with the one-year graft survival rates. Those patients with serum creatinine levels less than 2.4 mg/dl had one-year graft survival rates of over 80% compared with those with serum creatinine levels above 7.5 mg/dl after the first week who had one-year graft survival rates about 30% less. Intermediate serum creatinine values yielded intermediate one-year graft survival rates. 4. The cyclosporine dosage in the first month after transplantation varied considerably among the four centers studied here. These values were not directly correlated with the one-year graft survival rate, average serum creatinine levels or cumulative rejection rates in this preliminary examination. 5. Patients who rejected transplants 11 to 60 days posttransplant had been given lower cyclosporine dosages than those who rejected early or who had no rejections. 6. Although firm conclusions cannot be drawn from the small numbers of patients encompassed in this study, we hope the potential value of this type of analysis will be realized.

Differential control of U1 small nuclear RNA expression during mouse development

During normal mouse development the relative amounts of two types of U1 small nuclear RNA's (U1 RNA) change significantly. Fetal tissues have comparable levels of the two major types of mouse U1 RNA's, mU1a and mU1b, whereas most differentiated adult tissues contain only mU1a RNA's. Those adult tissues that also accumulate detectable amounts of embryonic (mU1b) RNA's (for example, testis, spleen, and thymus) contain a significant proportion of stem cells capable of further differentiation. Several strains of mice express minor sequence variants of U1 RNA's that are subject to the same developmental controls as the major types of adult and embryonic U1 RNA. The differential accumulation of embryonic U1 RNA's may influence the pattern of gene expression during early development and differentiation.

A teratocarcinoma-derived endoderm stem cell line (1H5) that can differentiate into extra-embryonic endoderm cell types

We investigated the ability of the teratocarcinoma-derived, epithelial-type cell line 1H5 to differentiate into either of the two pathways to primary endoderm, and tested the hypothesis that 1H5 represents a state similar to primitive endoderm in the late 4th-day blastocyst. Like other endodermal cell types, 1H5 cells mixed with embryonal-carcinoma cells sort out into "embryoid bodies" or structures that resemble 4th-day mouse embryos. The epithelial line conforms morphologically and biochemically to the few known characteristics typical of primitive endoderm. The present study demonstrates that the formation in vitro of overt visceral endoderm is readily achieved. The spontaneous arrangement of the cells into a cystic form is followed by the appearance of several markers of visceral endoderm, most notably alphafetoprotein, which is detected when 1H5 cells are cultured either in the presence of retinoic acid or when the cells interact with embryonal-carcinoma cells in a specific spatial arrangement after sorting out. However, some less specific properties of visceral endoderm are not expressed. Although 1H5 differentiates histologically into parietal-like endoderm in the tumor form, parietal cells cannot yet be identified with certainty in vitro because of the paucity of parietal-specific markers. The 1H5 cell line could provide a useful system for studying the characteristics and mechanisms underlying visceral-endoderm differentiation in vitro, since it has the distinct advantage that homogeneous cultures are produced, in contrast to other teratocarcinoma cell lines such as F9 which differentiate into a mixture of cell types.

Azathioprine-associated interstitial pneumonitis

Seven renal allograft recipients taking azathioprine (Imuran) for immunosuppression developed bilateral pulmonary infiltrates and a falling pO2 that did not respond to antibiotic therapy. Open lung biopsies revealed changes ranging from diffuse alveolar damage (DAD) to usual interstitial pneumonia (UIP) culminating in pulmonary fibrosis. There was no evidence of immune deposits, eosinophilia, vasculitis, granulomas, or microorganisms by cultures and appropriate stains. Following discontinuance of Imuran, the two cases with DAD revealed a significant clearing of the lung infiltrates, whereas four of five patients with UIP died while suffering from respirator-dependent ARDS. Biopsies showing hyaline membranes, intraalveolar edema and cuboidalization of alveolar epithelium were associated with total doses from 2,850 to 4,355 mg, whereas atypical epithelial hyperplasia, reorganization of distal air spaces, and fibrosis were noted in cases receiving from 5,600 to 28,625 mg of azathioprine. Ultrastructural changes were indistinguishable from those induced by other drugs causing pulmonary toxicity. In three cases atypical epithelial cells were detected cytologically in brushing specimens and appeared identical to those noted in the lung biopsies. Our findings are consistent with the view that azathioprine should be added to the list of agents capable of causing direct, dose-dependent pulmonary toxicity. Accordingly, drug-associated diffuse interstitial pulmonary disease should enter the differential diagnosis of a lung infiltrate that develops in renal transplant patients receiving Imuran.

Histocompatibility and isoenzyme differences in commercially supplied "BALB/c" mice

BALB/c mice obtained commercially were found to differ significantly from the standard phenotype of BALB/c strain mice. Isoenzyme tests and H-2 haplotype analyses indicated that the majority of mice from two of the three sources tested appeared mixed, frequently heterozygous, and did not consistently express either the expected H-2 or glucose phosphate isomerase type.

Autonomous gene expression on the human inactive X chromosome

Local derepression of the hpt locus on the human inactive X chromosome obtained in human female fibroblast x mouse L cell somatic cell hybrids was not correlated with the presence or absence of any specific human chromosome in the hybrids. Loss of the human active X, in particular, did not result in observable derepression of genes on the inactive X. Introduction of an active X, via a second hybridization of human cells having an active X with hybrid cells containing a locally derepressed X chromosome, did not restore repression of the derepressed hpt allele. The rate of hpt locus derepression in hybrid cells was estimated to be 10(-6) per inactive X chromosome per cell generation.

Ovarian localization by embryonal teratocarcinoma cells derived from female germ gells

Embryonal carcinoma cells derived from several different spontaneous ovarian teratocarcinomas of strain LT mice form tumors that are located exclusively, in many cases, in the ovaries of female mice. Embryonal cells previously unselected for site specificity localize in the ovaries regardless of route of entry of the cells, and produce very few tumors in males following intraperitoneal injections. The ovary tumors have been verified as originating from the injected cells by chromosomal and drug resistance markers, as well as by general in vitro growth characteristics. Cell-cell adhesion studies suggest specificity at the level of tumor cell-ovary organ cell interaction.

Radioimmunoassay for urinary albumin

We describe a rapid, sensitive, and precise radioimmunoassay for urinary albumin (Ualb). Aliquots of diluted urine were incubated at room temperature for 1 h with 125I-labeled albumin and a rabbit antiserum monospecific for human albumin. Phase separation was effected by the double-antibody technique. The dose-response curve as linear in the range of 15.6-10000 ng, equivalent to 4 to 3000 mg/liter of urine. The limit of sensitivity was 16 ng of albumin. The coefficient of assay variation was 4.8%, both at 44 mg/liter and at 1304 mg/liter. A displacement curve obtained with a serially diluted urine sample of high albumin concentration was completely superimposable with the curve for which human albumin was used as a standard. In 26 normal individuals the range for Ualb was 2.2--12.6 mg/24h, and for albumin clearance (Calb, 1.8 x 10(-5)-19.6 x 10(-5) ml/min. After renal homografts in 25 patients, Ualb ranged from 16.9 to 9928 mg/24 h, and Calb from 2.7 x 10(-4) to 1.7 x 10(-1) ml/min. Both increased Ualb and Calb correlated well with the severity of renal homograft rejection.

Radioimmunoassay for urinary albumin

We describe a rapid, sensitive, and precise radioimmunoassay for urinary albumin (Ualb). Aliquots of diluted urine were incubated at room temperature for 1 h with 125I-labeled albumin and a rabbit antiserum monospecific for human albumin. Phase separation was effected by the double-antibody technique. The dose-response curve as linear in the range of 15.6-10000 ng, equivalent to 4 to 3000 mg/liter of urine. The limit of sensitivity was 16 ng of albumin. The coefficient of assay variation was 4.8%, both at 44 mg/liter and at 1304 mg/liter. A displacement curve obtained with a serially diluted urine sample of high albumin concentration was completely superimposable with the curve for which human albumin was used as a standard. In 26 normal individuals the range for Ualb was 2.2--12.6 mg/24h, and for albumin clearance (Calb, 1.8 x 10(-5)-19.6 x 10(-5) ml/min. After renal homografts in 25 patients, Ualb ranged from 16.9 to 9928 mg/24 h, and Calb from 2.7 x 10(-4) to 1.7 x 10(-1) ml/min. Both increased Ualb and Calb correlated well with the severity of renal homograft rejection.

Adenine phosphoribosyltransferase and hypoxanthine-guanine phosphoribosyltransferase immunoprecipitation reactions in human-mouse and human-hamster cell hybrids

Male New Zealand White rabbits were immunized with human adenine phosphoribosyltransferase (APRT) and hypoxanthine-guanine phosphoribosyltransferase (HGPRT), which were purified about 2000-fold and 800-fold, respectively, from erythrocytes by DEAE-cellulose chromatography, ammonium sulfate precipitation and preparative polyacrylamide gel electrophoresis. Specific immunoprecipitations of APRT and HGPRT were achieved with the antisera that were obtained and by using polyethylene glycol as a substitute for goat anti-(rabbit) gamma globulin. The activities of the human forms of these enzymes, whether from red blood cells or from cultured cells, were almost completely eliminated under the conditions of immunoprecipitation used. Little or no reduction of APRT and HGPRT activities from mouse and Chinese hamster cells was observed. This discriminatory capacity of the antisera was successfully used for the identification of human APRT and HGPRT in human-mouse and human-hamster cell hybrids using the immunoprecipitation reaction.

Localized Derepression on the Human Inactive X Chromosone in Mouse-Human Cell Hybrids

Evidence for derepression of the gene for hypoxanthine phosphoribosyltransferase (HPRT; IMP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) on the human inactive X chromosome was obtained in hybrids of mouse and human cells. The mouse cells lacked HPRT and were also deficient in adenine phosphoribosyltransferase (APRT; AMP: pyrophosphate phosphoribosyltransferase; EC2.4.2.7). The human female fibroblasts were HPRT-deficient as a consequence of a mutation on the active X but contained a normal HPRT gene on the inactive X. The two human X chromosomes were further distinguished by differences in morphology: the inactive X was morphologically normal while the active X included most of the long arm of autosome no. 1 translocated to the distal end of the X long arm. Forty-one hybrid clones were first isolated by selection for the presence of APRT; when these clones were selected for HPRT, six of them yielded derivatives having human HPRT with incidences of about 1 in 10-6 APRT-selected hybrid cells. The HPRT-positive derivatives contained a normal-appearing X chromosome indistinguishable from the inactive X of the parental human fibroblasts. The active X with the translocation was not found in any of the HPRT-positive hybrid cells. Human phosphoglycerokinase (ATP:3-phospho-D-glycerate 1-phosphotransferase. EC 2.7.2.3) and glucose-6-phosphate dehydrogenase (D-glucose 6-phosphate: NADP 1-oxidoreductase, EC 1.1.1.49), which are specified by X-chromosomal loci, were not detected in the hybrids expressing HPRT even though they contained an apparently intact X chromosome. The observations are most simply explained by the infrequent, stable derepression of inactive X chromosome segments that include the HPRT locus but not the phosphoglycerokinase and glucose-6-phosphate dehydrogenase loci.

The locus for human adenine phosphoribosyltransferase on chromosome no. 16

Evidence for assigning the locus determining the structure of adenine phosphoribosyltransferase (APRT) to human chromosome No. 16 is presented. Hybrids of APRT-deficient mouse cells and of human fibroblasts having normal APRT were isolated by fusing the parental cells with Sendai virus, blocking de novo purine nucleotide synthesis with azaserine and selecting for hybrids that could use exogenous adenine. The hybrid clones that were studied had only APRT activity that was indistinguishable from human APRT with regard to electrophoretic migration and reaction with antibodies against the partially purified human enzyme. No. 16 was the only human chromosome consistently present in all of the clones, and in one clone, it was the only human chromosome detected. Selection against hybrid cells with 2,6-diaminopurine (DAP) yielded DAP-resistant survivors that lacked chromosome No. 16. One hybrid that originally had an intact No. 16 yielded adenine-utilizing subclones that lacked No. 16 but had a new submetacentric chromosome. The distribution of centromere-associated heterochromatin and the fluorescence pattern indicated that this chromosome consisted of a mouse telocentric chromosome and the long arm of No. 16. Cells having the submetacentric chromosome had human APRT. Both the enzyme and the chromosome were absent in DAP-resistant derivatives. These results suggest that the structure of APRT is defined by a locus on the long arm of human chromosome No. 16.