DNA sequence analysis of Sry alleles (subgenus Mus) implicates misregulation as the cause of C57BL/6J-Y(POS) sex reversal and defines the SRY functional unit.

The Sry (sex determining region, Y chromosome) open reading frame from mice representing four species of the genus Mus was sequenced in an effort to understand the conditional dysfunction of some M. domesticus Sry alleles when present on the C57BL/6J inbred strain genetic background and to delimit the functionally important protein regions. Twenty-two Sry alleles were sequenced, most from wild-derived Y chromosomes, including 11 M. domesticus alleles, seven M. musculus alleles and two alleles each from the related species M. spicilegus and M. spretus. We found that the HMG domain (high mobility group DNA binding domain) and the unique regions are well conserved, while the glutamine repeat cluster (GRC) region is quite variable. No correlation was found between the predicted protein isoforms and the ability of a Sry allele to allow differentiation of ovarian tissue when on the C57BL/6J genetic background, strongly suggesting that the cause of this sex reversal is not the Sry protein itself, but rather the regulation of SRY expression. Furthermore, our interspecies sequence analysis provides compelling evidence that the M. musculus and M. domesticus SRY functional domain is contained in the first 143 amino acids, which includes the HMG domain and adjacent unique region (UR-2).

C57BL/6J-T-associated sex reversal in mice is caused by reduced expression of a Mus domesticus Sry allele.

C57BL/6J-T-associated sex reversal (B6-TAS) in XY mice results in ovarian development and involves (1) hemizygosity for Tas, a gene located in the region of Chromosome 17 deleted in T(hp) and T(Orl), (2) homozygosity for one or more B6-derived autosomal genes, and (3) the presence of the AKR Y chromosome. Here we report results from experiments designed to investigate the Y chromosome component of this sex reversal. Testis development was restored in B6 T(Orl)/+ XY(AKR) mice carrying a Mus musculus Sry transgene. In addition, two functionally different classes of M. domesticus Sry alleles were identified among eight standard and two wild-derived inbred strains. One class, which includes AKR, did not initiate normal testis development in B6 T(Orl)/+ XY mice, whereas the other did. DNA sequence analysis of the Sry ORF and a 5' 800-bp segment divided these inbred strains into the same groups. Finally, we found that Sry is transcribed in B6 T(Orl)/+ XY(AKR) fetal gonads but at a reduced level. These results pinpoint Sry as the Y-linked component of B6-TAS. We hypothesize that the inability of specific M. domesticus Sry alleles to initiate normal testis development in B6 T(Orl)/+ XY(AKR) mice results from a biologically insufficient level of Sry expression, allowing the ovarian development pathway to proceed.

Migration of mesonephric cells into the mammalian gonad depends on Sry.

In mammals, the primary step in male sex determination is the initiation of testis development which depends on the expression of the Y-linked testis determining gene, Sry. The mechanisms by which Sry controls this process are unknown. Studies showed that cell migration from the adjacent mesonephros only occurs into XY gonads; however, it was not known whether this effect depended on Sry, another Y-linked gene, or the presence of one versus two X chromosomes. Here we provide genetic proof that Sry is the only Y-linked gene necessary for cell migration into the gonad. Cell migration from the mesonephros into the differentiating gonad is consistently associated with Sty's presence and with testis cord formation, suggesting that cell migration plays a critical role in the initiation of testis cord development. The induction of cell migration represents the earliest signaling pathway yet assigned to Sry.

Metabolic factors have a major impact on kidney allograft survival.

BACKGROUND: At the present time, late graft loss is the major cause of kidney failure after transplantation. However, the influence of metabolic factors on this process is ill-defined. METHODS: To identify the impact of lipid metabolism, glucose metabolism, and blood pressure and their prognostic value for graft survival, data for all recipients of a kidney allograft with a potential graft survival of >15 years and a minimum graft survival of 1 month were analyzed retrospectively. Recipients of kidney grafts functioning more than 15 years (n=32) were compared with those with a graft function of less than 10 years (n=152, controls) and evaluated in a multivariate analysis. RESULTS: Low levels of serum cholesterol, triglycerides, and glucose, before and after transplantation, were accompanied by a prolonged graft survival. Prognostic factors for early graft failure included serum triglycerides >300 mg/dl, cholesterol >250 mg/dl before transplantation, serum creatinine >4.0 mg/dl 1 month after transplantation, and donor age above 45 or less than 10 years. Additionally, systolic and, particularly, diastolic blood pressure was lower in the group with a prolonged graft function as compared with controls immediately before and after transplantation. In addition, the incidence of primary graft function was lower and the incidence of acute rejection episodes higher in controls. Cold and warm ischemic time, body mass index, recipient age, and gender did not differ significantly. CONCLUSIONS: Our data suggest that metabolic parameters play an important role in the process of late graft loss after kidney transplantation.

[The pulsatile flow index (PFI) in the diagnosis of dysfunctional kidney transplants]. / Der Pulsationsflussindex (PFI) in der Diagnostik dysfunktioneller Nierentransplantate.

In 61 patients (167 examinations) the pulsatile flow index (PFI) was used to diagnose the cause of renal transplant dysfunction. The results were correlated with histology and clinical course and outcome, angiography or quantitative radionuclide renography. Renal transplant rejection was diagnosed by PFI with a sensitivity of 85%. The specificity was 81% and the diagnostic accuracy 83%. The positive predictive value was found to be 76%, whereas the negative predictive value was 89%. In presence of acute tubular necrosis (ATN) the PFI was normal in 89% of examinations and therefore distinguishable from acute rejection.

[Differential diagnostic evaluation of a dysfunctional kidney transplant by magnetic resonance tomography]. / Differentialdiagnostische Abklärung des dysfunktionellen Nierentransplantats durch die Kernspintomographie.

Immediate diagnosis of rejection is essential for the prognosis of a renal transplant. To differentiate between rejection and acute tubular necrosis, 48 examinations (31 patients) were evaluated by Magnetic Resonance Imagining and Duplex Doppler ultrasound, and compared to the clinical outcome and histology. Sensitivity of MRI and Duplex Doppler was 82% (14/17), specificity was 77% (24/31) and 84% (26/31), respectively. Even when the results of both methods matched well, due to the extensive financial and technical efforts MRI may only be used as an additional tool for diagnosis.

[The effect of obesity on outcome of kidney transplantation]. / Der Einfluss der Adipositas auf die Ergebnisse der Nierentransplantation.

BACKGROUND AND AIM: Obesity is a risk factor for postoperative complications in surgery. In a retrospective study we investigated the course of body weight during the waiting period and the first postoperative year and the influence of obesity on graft function. PATIENTS AND METHOD: The medical records of 334 adult patients undergoing cadaveric kidney transplantation between 1986 and 1992 were reviewed. Immunosuppression was performed with cyclosporine and prednisone. For all patients the Broca index was calculated with the relative body weight by the formula: body weight/Broca index x 100 (% BI). Obesity was defined as relative body weight > or = 120% BI. RESULTS: At the time of the indication for kidney transplantation 15.3% of the patients were obese. Only 12 of these 51 obese patients reduced their body weight below 120% BI until transplantation, whereas 25 patients increased weight in excess of 120% BI. Thus the number of obese patients raised to 19.2% by the time of transplantation. The graft survival in the obese group was significantly lower than in the nonobese group. This difference appeared already in the first half year after transplantation being constant in the following time. The resulting 1-year graft survival was 82.8% and 91.4% respectively (p < 0.05). During the first year 59 patients more became obese, the percentage of obese raised up to 36.0%. One year after transplantation there was no longer significant difference of graft survival rate in the further follow-up between obese and nonobese patients. CONCLUSION: Our findings show, that obesity is an important risk factor for early graft loss. Therefore all participating physicians assume a great responsibility for the pre-operative treatment during the waiting time.

Evidence that Sry is expressed in pre-Sertoli cells and Sertoli and granulosa cells have a common precursor.

The expression of Sry in the undifferentiated, bipotential genital ridges of mammalian XY fetuses initiates testis development and is hypothesized to do so by directing supporting cell precursors to develop as Sertoli cells and not as granulosa cells. To directly test this hypothesis, transgenic mice expressing EGFP under the control of the Sry promoter were produced. After establishing that the transgene was expressed in fetal gonads similarly to endogenous Sry, the spatial and temporal expression of the Sry-EGFP transgene was investigated in developing gonads by using confocal microscopy and immunofluorescent histochemistry. This analysis indicated: (1) Sry is first expressed in cells located centrally in the genital ridge and then later in cells located at the cranial and caudal poles, (2) Sry is expressed exclusively in pre-Sertoli cells in the urogenital ridge, and (3) Sertoli and granulosa cells develop from a common precursor. These results support the hypothesis that Sry initiates testis differentiation by directing the development of supporting cell precursors as Sertoli rather than granulosa cells. Furthermore, the Sry expression pattern explains the nonrandom distribution of testicular and ovarian tissue in mammalian ovotestes.

Model experiments on the effect of bifurcations on capillary blood flow and oxygen transport.

O2-delivery by a single capillary is a function of the flow rate and the fraction of flow made up of red blood cells. Capillary flow rate in turn depends upon flow resistance which is determined by the fraction of capillary volume occupied by red blood cells. Experiments were carried out to study the relationship between these parameters in an in vitro model consisting of glass capillaries (I.D. 3.3--11.0 micrometer) branching from a large bore feeding channel which was perfused at variable flow rates with suspensions of human red cells with different hematocrits. Capillary flow rates ranged from 0--10(-4) mm3s-1. The results indicate that the red cell flow fraction increases with increasing capillary flow rate and with decreasing feeding vessel flow rate. Capillary volume fraction occupied by red cells similarly depends on these two parameters, but is consistently lower than the red cell flow fraction. Capillary flow resistance increases with flow rate due to increasing volume fraction of cells. If the results obtained with the model system are applicable to in vivo capillaries it must be concluded that O2-delivery by a single capillary is not linearly related to flow rate but increases more than proportionately with flow rate. Due to alteration of resistance with flow rate another type of "autoregulation" of capillary flow is proposed which tends to keep flow rate constant despite changes of driving pressure.

Motion, deformation, and interaction of blood cells and plasma during flow through narrow capillary tubes.

The microrheological characteristics of human blood cell suspensions flowing through very narrow glass capillaries (I.D. 5-12 microns) have been investigated using a traveling capillary method. In addition, red cell shape during flow was studied after cell fixation during capillary passage. The observations and measurements indicate the following: 1. The deformed shape of human red cells is not axisymmetrical and develops from an edge-on-oriented biconcave disc shape. 2. Red cells tend to travel in groups rather than equally spaced, presumably due to interindividual differences in size, shape, and deformability. 3. Red cell rotation in 8-12 microns capillaries occurs only if the flow forces are too small to induce cell deformation; during rotation of biconcave discs a substantial fraction of orbiting times is spent in an edge-on orientation; rotation is more frequently observed if the deformability of the erythrocytes is reduced. 4. Hematocrit-dependent transition from single-file to multi-file ('zipper') flow is observed in tubes whose inner diameter exceeds approximately 6 microns. 5. The flow pattern in the larger capillaries (8-12 microns) is characterized by significant variation of both radial and axial velocity of individual cells, as well as by concomitant changes of cell shape. However, cell-to-cell interactions and changes of cell orientation become progressively less significant in even smaller capillary tubes. 6. The bolus motion of intercellular plasma can be demonstrated by using microspheres or single platelets flowing between red cells as indicators. 7. Single platelets flowing between erythrocytes exhibit considerable variation in axial velocity in addition to rapid rotation.