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Biomedical subjects

K H Stenzel

Publications and source records attributed to K H Stenzel.

At least 163 records · Page 9Linked to original sources

Deposition of platelets and fibrin on chemically modifide collagen hollow fibers.

A new technique was devised for interaction studies between human blood and chemically modified amorphous collagen surfaces. Blood is drawn directly from an antecubital vein, through saline-filled collagen hollow fibers, at either constant flow for varying time or constant time at varying flow. Platelets and fibrin were deposited more rapidly and in greater numbers on methylated surfaces and more slowly and to a lesser extent on succinylated surfaces than on native surfaces. Increasing blood flow was associated with increased fibrin formation. Adherent platelets spread over 3-8 mu of methylated surface, but retained a spherical shape (1-2 mu) on succinylated and native surfaces. Thus, charge modification of collagen significantly alters platelet adhesion, subsequent platelet morphology, and fibrin deposition. Methylated surfaces are thrombogenic and succinylated ones are relatively thrombo-resistant.

Biocompatible Materials↗

Hepatitis B "immune" globulin: effectiveness in prevention of dialysis-associated hepatitis.

A randomized, double-blind, multicenter study of hepatitis prevention by immune serum globulin with high anti-HBs titer ("hepatitis B immune globulin") was carried out among 318 new patients and 296 staff members of renal dialysis units. Three milliliters of high titer globulin, repeated at four months, was compared with equal doses of intermediate or normal titer globulin. Among staff members, the cumulative percentages developing hepatitis or HBs Ag, or both, within eight months were 6.9, 11.7, and 11.1 in the high, intermediate, and normal titer groups respectively. The lower incidence associated with high titer globulin was not significant (P greater than 0.05). However, among the patients the respective percentages were 7.9, 21.3, and 23.1 and the lower incidence in the high titer globulin group was significant.

Antibodies↗

Deposition of blood cells on collagen and cuprophane membranes.

Dogs were dialyzed with collagen and cuprophane membranes, human renal failure patients were dialyzed with cuprophane membranes, and samples of the membranes were observed by scanning electron microscopy at different time periods. Fixation was done in glutaraldehyde and cacodylate buffer, and samples were dried at the critical point. All cellular elements were well preserved and appeared viable. Cuprophane adsorbed platelets almost selectively in dog dialyses, whereas collagen adsorbed a smaller number and more heterogeneous group of cells. In contrast to these findings, when cuprophane was used in clinical dialyses, the cell population was predominantly polymorphonuclear leukocytes.

Adsorption↗

Clinical effects of bilateral nephrectomy.

The effects of removal of all renal tissue on hematopoiesis, osteodystrophy, blood pressure regulation and metabolic functions are reviewed; and, the indications for, and results of, bilateral nephrectomy are discussed. Nephrectomy results in a more severe anemia in dialysis patients which is poorly responsive to androgen therapy. No differences were detected in the severity of osteodystrophy between nephric and anephric patients. However, bilateral nephrectomy can occasionally result in the acute onset of hypocalcemia. Blood pressure regulation must be accomplished in the absence of a functioning renin-angiotensin system. This is largely on the basis of volume, but changes in vascular tone may also be significant. Little is known about the metabolic consequences of nephrectomies. The effect on substances metabolized by the kidney is an area for further investigation. Kidney tissue should be preserved, if at all possible, and nephrectomy performed only for specific indications.

Adult↗

Improved renal allograft survival using the mixed lymphocyte culture for selection of nonidentical living related donors.

Our results concur with earlier published work, by other groups, showing that LRD-recipient pairs with low MLC stimulation usually have better and more prolonged graft success than do those with higher stimulation. Specific HL-A compatibilities or incompatibilities did not seem to affect these results, nor did the presence of an increased number of common loci, short of increasing the apparent chromosome compatibility. The presence of pre-transplant cytotoxic antibodies, in patients with a high MI, however, may unfavorably affect the LRD transplant. The overall results of our LRD transplant experience is shown in Figure 1, and superimposed upon Figure 2, is the current extrapolation of data showing MLC stimulation and haplotype success. Thus, it appears that graft survival may be improved and more closely approach the levels seen in a full-house, diplotype match, by using the MLC results in considering patients for transplantation. Not all patients with a high MLC, however, (see table) reject their grafts and it is impossible to predict pre-transplant who will develop specific allograft enhancement. Before the MI becomes a specific criteria for transplant selection, additional studies of patient stimulation in MLC should be done. Suppression of stimulation by donor cells in autologous serum, as compared to the response to unrelated controls, might provide pre-transplant clues to the presence of enhancing factors. Such studies could provide an index that would be more meaningful than the MI in AB sera alone. Since overall results from both our series and from the Transplant Registry continue to indicate better long term graft survival for LRD than for cadaver transplants, and since the evidence suggests that a successful transplant offers a patient a better quality of life, as well as decreased morbidity and mortality compared to concomitant time spent on hemodialysis, continued LRD transplants with high MI is warranted in some circumstances with the patient's understanding of the overall outcome and backgrouns. Until in vitro tests can be more predictive of individual rather than statistical graft success, the patient with an LRD and a high MI should be given a complete explanation of the probabilities for success or failure, and he and the donor allowed to make an informed decision. The following are guidelines that we proposed for the selection of LRD transplants: 1. Availability and willingness. 2. Medical and psycho-social clearance. 3. ABO compatibility. 4. Negative direct crossmatch. 5. HL-A diplotype or haplotype. 6. MI less than 10 if possible, with or without HL-A antibodies. 7. MI greater than 10 with no HL-A antibodies, if possible. 8. MI greater than 10, with HL-A antibodies, if both donor and recipient clearly understand the enhanced chance for failure.

ABO Blood-Group System↗

Effects of intravenous methylprednisolone on mixed lymphocyte cultures in normal humans.

Mixed-lymphocyte-culture response and peripheral lymphocyte counts were determined after 100 mg and 1,000 mg of methylprednisolone were administered intravenously to healthy volunteers; The MLC response was significantly suppressed in both groups for at least 12 hr. The degree of suppression of the MLC response did not differ between the two groups. Lymphocytopenia persisted for at least 24 hr. The MLC response, however, returned to its full capacity within 24 hr. In the low-dose group this response showed a marked rebound phenomenon at 24 hr. These findings indicate that methylprednisolone has a profound inhibitory effect on lymphoid cells' response to allogenic stumli in the MLC system.

Adult↗

Kidney transplantation: Improvement in patient and graft survival.

Patient and graft survival were reviewed in a series of 249 kidney transplants done from 1963 to March 1973. Patient survival was calculated by the life table method for the periods 1963-1970, and 1970-1973, since in 1970 a formal Kidney Center was established and mortality rates changed. Graft survival was analyzed in terms of donor source, HL-A matching and immune responsiveness to HL-A antigens. Three-year predicted mortality for cadaver kidney recipients was 62% between 1963 and 1969 (42 patients) and 8% between 1970 anid 1973 (67 patients). Similar predicted mortality for related living donors was 30% between 1963 and 1969 (52 patients) and 14% between 1970 and 1973 (85 patients). Mortality has continued to decrease and there has been only one death in the last 87 consecutive transplants, including 57 consecutive cadaver transplants. Oneyear predicted kidney survival for the 10-year period is 44% for cadaveric, 60% for non HL-A identical related living and 90% for HL-A identical sibling donors. In the cadaver group, those sharing 2 or more HL-A antigens had the same kidney survival as the non HL-A identical related living donor grafts. Since cadaver graft recipients are on dialysis for a longer period of time, immune responsiveness can be detected by their response to blood transfusions, whereas this determination could not be made in our related living donor group. Non-responsive cadaver kidney recipients had 80% one year kidney survival. We conclude that transplant mortality can be reduced to less than 10% by the Center approach to treatment of renal disease, dialysis does not adversely affect future transplantation, and excellent (80%) kidney survival can be expected in properly selected cadaver graft recipients.

Blood Transfusion↗