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Biomedical subjects

D Kahn

Publications and source records attributed to D Kahn.

At least 181 records · Page 10Linked to original sources
PubMed1994

Placement of a double lumen silastic catheter for hemodialysis access through the cephalic vein.

The cephalic vein within the deltopectoral groove provides adequate access to the central venous system for the PermCath hemodialysis catheter. Unlike EJV techniques, which are successful in few instances, the cephalic vein approach was successful in approximately 75 percent of instances. In addition, the rate of complications secondary to bleeding or catheter kinking are decreased with the cephalic vein technique as compared with insertion through the EJV or IJV. We conclude that the cephalic vein is a dependable and functional approach to the central venous system for the PermCath hemodialysis catheter.

Adult↗
PubMed1993

Disordered hemostasis in extrahepatic portal hypertension.

To assess the contribution of naturally occurring portal-systemic shunts to the coagulopathy of patients with liver disease, we studied laboratory parameters of hemostasis in 20 adult patients with extrahepatic portal hypertension, secondary to portal vein thrombosis, that had resulted in variceal bleeding. All extrahepatic portal hypertension patients had normal liver function and histological appearance. None had any evidence of preexisting coagulation disorders, and none had bled or undergone sclerotherapy in the 6 mo before study. Age- and gender-matched groups of 20 healthy individuals and 20 stable patients with cirrhosis and portal hypertension who had a history of variceal bleeding served as controls. Both patient groups had thrombocytopenia consistent with hypersplenism and portal hypertension. Prothrombin international normalized ratio (extrahepatic portal hypertension, 1.3 +/- 0.12; cirrhosis, 1.7 +/- 0.2; control, 1.02 +/- 0.06; p < 0.05) and partial thromboplastin time ratios (extrahepatic portal hypertension, 1.12 +/- 0.1; cirrhosis, 1.26 +/- 0.2; controls, 1.01 +/- 0.03; p < 0.05) were significantly prolonged in both patient groups. Extrahepatic portal hypertension and cirrhotic patient groups had significantly increased levels of serum total fibrin(ogen)-related antigen (extrahepatic portal hypertension, 818 +/- 150 ng/ml; cirrhosis, 454 +/- 52 ng/ml; controls, 124 +/- 7.3 ng/ml; p < 0.05), fibrin monomer (extrahepatic portal hypertension, 168.8 +/- 16.9 ng/ml; cirrhosis, 115.6 +/- 11.1 ng/ml; controls, 19.7 +/- 0.4 ng/ml; p < 0.05) and D-dimer (extrahepatic portal hypertension, 118 +/- 9.6 ng/ml; cirrhosis, 129 +/- 10 ng/ml; controls, 53.2 +/- 1.6 ng/ml; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Renal transplantation in patients with bilateral renal carcinoma--how long should we wait?

Patients with bilateral renal carcinoma or malignancy in a solitary kidney are best managed by radical nephrectomy with subsequent dialysis and transplantation. Because of the risk of recurrence of the tumour, the timing of the transplant procedure is important. We report on two patients with bilateral renal carcinoma who were subjected to radical nephrectomy and then managed with dialysis and transplantation within 6 months.

Adenocarcinoma↗
PubMed1993

Control involving metabolism and gene expression: the square-matrix method for modular decomposition.

Control of DNA supercoiling by the free-energy of hydrolysis of ATP that involves gene expression is analyzed in terms of three levels of unconnected metabolic pathways. These are synthesis and breakdown of topoisomerase mRNAs, synthesis and breakdown of topoisomerase proteins and supercoiling and relaxation of DNA. The so-called square-matrix method previously developed for the control of metabolic pathways, is extended to deal with this hierarchical control system. It turns out that also in this case, the matrix of control coefficients is equal to the inverse of the so-called elasticity matrix, which contains all relevant elasticity coefficients as well as information about the structure and connectedness of the pathways involved. For a simpler case of a hierarchy of two systems, we demonstrate that the explicit matrix inversion method may be replaced by an implicit in which the regulatory effects that run through the other level are described by an additional elasticity coefficient which may then be treated as if local.

Adenosine Triphosphate↗
PubMed1993

Gender of donor influences outcome after orthotopic liver transplantation in adults.

Because male and female livers not only differ with respect to estrogen and androgen receptor content, but also demonstrate sexual dimorphism of certain functions, we examined the effect of donor gender on graft survival following liver transplantation (OLTx) in adults. Between February 1981 and February 1988, 982 OLTx procedures were performed in 789 adult patients at the University of Pittsburgh. In this study, OLTx was categorized as a failure if the patient died or required retransplantation within 60 days of the surgery. When the donor-recipient gender combinations were male-male, male-female, and female-female, the failure rates were 28%, 28%, and 36%, respectively. In contrast, 60% of female donor livers failed in male recipients. Compared to the pooled donor-recipient gender combinations, the odds of failure for female-male liver grafts were increased 3.7-fold (95% confidence interval: 6.5, 2.1; P < 0.001). These findings may result, at least in part, from alterations in the sex hormone milieu or changes in the graft estrogen or androgen receptor content.

Adult↗
PubMed1993

Modular analysis of the control of complex metabolic pathways.

The understanding of the functioning of the intact cell would be simplified appreciably if it were possible first to analyze particular modules of cell physiology separately, and then to integrate the information so as to yield understanding of the control structure in terms of the mutual regulation of the modules. Here we develop a quantitative method based on Metabolic Control Analysis that makes this possible: The relevant properties of the modules are contained in "overall" elasticity coefficients, which reflect the changes in fluxes in the module upon a small variation of the environment of the module, allowing the latter to attain steady state. We show how overall control coefficients, which reflect the control exerted by the processes catalyzed by each module, can be expressed into the overall elasticity coefficients. We derive corresponding summation and connectivity theorems. A number of possible divisions of physiological systems into modules is discussed. This work is a generalization of previous analyses of overall control properties in that it allows for multiple fluxes to connect the modules, and reaction stoichiometries of any complexity.

Cell Physiological Phenomena↗
PubMed1993

An emission-based technique for obtaining attenuation correction data for myocardial SPECT studies.

In this paper, a technique is described for obtaining the information needed to perform attenuation correction in the thorax entirely from an emission study. This technique is based on the observation that the variation in soft tissue and lung attenuation coefficients is small among individuals. Thus only the outer contours of the body and lungs need be determined for obtaining the attenuation map. The contours are determined by using 99Tcm-macroaggregated albumin (MAA) to locate the lungs and an external source wrapped about the chest to locate the body boundary. Simulation studies were performed to investigate how errors in the presumed tissue attenuation coefficients affect the accuracy of the correction. Body and lung attenuation coefficients were varied from 20% less to 20% more than the coefficients used in the corrections. Over this range, there was less than a 15% alteration in the relative distribution of counts in the left ventricle. To test clinical feasibility, seven patients referred for clinical myocardial perfusion studies were scanned before and after the placement of the body source and the administration of 99Tcm-MAA. Reconstructed images from these studies showed clear demarcation of all body and lung boundaries. The presence of 99Tcm-MAA in the lungs had no significant effect on the clinical interpretation of the single photon emission computed tomographic (SPECT) studies. It is concluded that this technique is feasible for clinical application and that it offers important advantages over other current methods.

Adult↗
PubMed1993

The genes of the glutamine synthetase adenylylation cascade are not regulated by nitrogen in Escherichia coli.

Regulation of glutamine-synthetase (GS) activity in enteric bacteria involves a complex cascade of events. In response to nitrogen limitation, a transferase catalyses the uridylylation of the PII protein, which in turn stimulates deadenylylation of GS. Deadenylylated GS is the more active form of the enzyme. Here we characterize in detail the genes from Escherichia coli encoding uridylyl-transferase (glnD), the PII protein (glnB), and adenylyl-transferase (glnE). glnD is transcribed from its own promoter, glnE is contranscribed with another gene, orfXE, whereas glnB is partly contranscribed with a gene encoding a homologue of the transcription activator NtrC. All three gln regulatory genes were constitutively expressed at a low level, i.e. their expression was independent of the nitrogen status and the RNA polymerase sigma factor sigma 54. We conclude that the functioning of the GS adenylylation cascade is regulated by modulation of the activities of uridylyl-transferase and adenylyl-transferase, rather than by changes in the expression of their genes.

Amino Acid Sequence↗
PubMed1993

Transplantation for diabetic nephropathy at Groote Schuur Hospital.

Over a period of 6 years, 9 patients with diabetic nephropathy received renal allografts at Groote Schuur Hospital. This low figure represents 2.8% of the total number of renal transplants done at our institution, and is evidence of concern about the apparent poor results of transplantation in these patients. After 2 years, patients and graft survival rates in diabetics were 87% and 62% respectively. Vascular disease was a major problem. Six patients developed limb gangrene, and symptomatic coronary and cerebrovascular disease developed in 2 patients. Infections were common and included wound sepsis, cellulitis, candidiasis and urinary tract infections. Diabetes was poorly controlled after transplantation in 5 patients. Proliferative retinopathy was present in 6 patients but remained stable after transplantation. Despite very strict selection criteria, the results of renal transplantation in diabetic patients remain poor. Better treatment strategies are needed to justify acceptance of these patients for transplantation.

Adult↗
PubMed1993

Public attitudes to organ donation in South Africa.

Public attitudes to organ donation may be influenced by cultural beliefs as well as racial prejudices and superstitions. In South Africa we are able to examine these issues from both a First- and a Third-World perspective. In this study the attitudes of 1 299 urban white, 625 rural black and 826 urban black South Africans were examined. Eighty-nine per cent of white, 84% of rural black and 76% of urban black South Africans are prepared to donate their own organs. All groups are less willing to donate the organs of close relatives (76% white, 76% rural black and 67% urban black). Most people felt that this decision should be made by the person before death. Most black people (88%) felt that the race of both donor and recipient were irrelevant. Only 23% of black people were prepared to donate their corneas, compared with the 69% and 70% willing to donate their kidneys and heart respectively.

Adolescent↗
PubMed1992

New rapid technique for renal transplantation in the rat.

Present techniques for renal transplantation in the rat include a period of 20-25 minutes warm ischemia. Our method combines a recently described sleeve anastomotic technique for the renal artery, conventional end-to-end anastomosis of the renal vein, and implantation of the ureter into the bladder. This has resulted in a reproducible ischemic interval of 12-14 minutes. Plasma creatinine and histological features in animals sacrificed from 10 to 30 days after transplantation were within normal limits with no evidence of ischemic damage. A further advantage of the technique is that kidneys can be exchanged between the donor and recipient. It is recommended that this procedure, which reduces the ischemic interval by up to 50%, should be learned and employed in studies of renal transplantation in the rat, especially if such studies include the prior administration of cyclosporine, which may aggravate the effects of ischemia.

Anastomosis, Surgical↗
PubMed1992

DTPA renal scan assessment of renal allograft dysfunction in rats.

The precise cause of allograft dysfunction after renal transplantation often cannot be established by non-invasive means. In clinical practice, radionuclide scans form an integral part of the clinician's armamentarium in the assessment of these patients. Unfortunately, in the clinical setting more than one pathological process may be responsible for the impaired function, making it difficult to correlate the scan appearances with the pathology. In this study in rats we compared the renal DTPA scan appearances of the various pathological processes which may cause renal allograft dysfunction in the immediate post-transplant period.

Animals↗