Search PubMed⌕ Search

Biomedical subjects

R A Kahn

Publications and source records attributed to R A Kahn.

At least 127 records · Page 7Linked to original sources
PubMed1982

Requirements for cholera toxin-dependent ADP-ribosylation of the purified regulatory component of adenylate cyclase.

The requirements for cholera toxin-catalyzed ADP ribosylation of the purified regulatory component of adenylate cyclase are described. In addition to the toxin, this reaction is dependent on or is facilitated by NAD, GTP, phospholipid, and a factor found associated with plasma membranes from several sources. Factor activity is heat-labile and protease-sensitive but is unaffected by treatment with N-ethylmaleimide. Gel filtration indicates that the factor behaves as a monodisperse species with a Stokes radius of 3.2 nm. The factor thus appears to be a protein that is distinct from any of the known components of adenylate cyclase. Factor activity was also detected in the cytoplasm of S49 cells. The cytoplasmic factor was smaller (Stokes radius = 2.0 nm) than the membrane-derived factor, and it was inactivated in the presence of sodium cholate. The initial rate of activation of the regulatory component of adenylate cyclase by toxin was found to be linearly related to the amount of factor present in the reaction. This has allowed the quantitation and partial purification (33-fold from detergent extracts) of the factor from turkey erythrocyte membranes.

Adenosine Diphosphate Ribose↗
PubMed1982

The distribution of serum alanine aminotransferase levels in a blood donor population.

The authors studied the distribution of alanine aminotransferase (ALT) levels in 10,034 volunteer blood donors. The mean +/- SD ALT value was 21.4 +/- 19.3 IU/liter; 549 (5.5%) of the donors had a ALT value greater that 45 IU; 2.5 per cent had ALT values greater than 60 IU. In general, ALT levels were higher in males than in females, and were age related; peak values occurred in the third decade of life for males and between 50-60 years of age in females. ALT values greater than 45 IU were found significantly more often in males, in donors of both sexes 30-40 years of age, in married donors, in non-Caucasians, and in those whose education level was no higher than high school. Follow-up samples in donors with an initial ALT greater than 45 IU, revealed that 67% continued to have ALT values above 45 IU 2-8 weeks following initial sampling, and 40% had an ALT greater than 45 IU when tested again six months after entry into the study. ALT values greater than 60 IU were associated with a significantly increased prevalence of antibody of hepatitis B surface antigen (anti-HBs) and antibody to hepatitis B core antigen (anti-HBc) occurring together. No statistically significant association was found between transaminase activity and the prevalence of anti-HBs or anti-HBc alone, or with hepatitis A antibody. These findings demonstrate that there are defined sociodemographic and serologic features of donors with elevated ALT values.

Age Factors↗
PubMed1981

Serum alanine aminotransferase of donors in relation to the risk of non-A,non-B hepatitis in recipients: the transfusion-transmitted viruses study.

To evaluate the incidence of post-transfusion hepatitis and factors influencing its occurrence, the Transfusion-Transmitted Viruses Study prospectively followed 1513 transfusion recipients from 1974 through 1979. The attack rate for non-A,non-B hepatitis was 10 per cent. The incidence of hepatitis was directly related to the alanine aminotransferase (ALT) level in blood donors. In recipients of multiple transfusions of blood that had no donor-ALT level above 29 IU per liter the attack rate was 6 per cent or less; at higher donor-ALT levels the attack rate increased progressively, reaching 45 per cent in recipients of units with an ALT of 60 IU or greater. A similar relation was observed among recipients of single units of blood. Moreover, hepatitis developed in 10 of 11 recipients of two units with an ALT level of 45 IU or greater. These data indicate that screening blood for ALT levels would reduce the incidence of non-A,non-B post-transfusion hepatitis.

Adolescent↗
PubMed1981

Detection and characterization of monoclonal antibodies to platelet membrane proteins.

We have devised a solid-phase radioimmunoassay for the detection and characterization of monoclonal antibodies directed against platelet surface antigens. Platelet membrane proteins, solubilized with 0.1% Triton X-100, were covalently coupled to cyanogen bromide (CNBr)-activated filter paper disks that were than used as the support in antibody binding assays. SDS PAGE of solubilized membrane proteins taken immediately before and after incubation with activated disks indicated that representative amounts of each membrane protein were bound to the disks. Either monoclonal or heterologous anti-platelet antibody could be detected on disks that had been prepared using as little as 50 micrograms of membrane protein per 100 disks. For the detection of antibody, disks were incubated with test sera for 2 h, washed, and incubated with 125I-labeled anti-immunoglobulin G, and the amount of bound radioactivity was determined. The sensitivity of the disk assay in detecting monoclonal antibodies was far greater than that of a corresponding radioimmunoassay that used whole platelets as the solid phase. By linking other proteins such as fibrinogen or anti-mouse subclass specific antisera to CNBr-activated disks, the method was adapted for antibody characterization. The sensitivity and ease with which the assay can be performed make this technique most suitable for screening and characterizing monoclonal antibodies.

Antibodies↗
PubMed1981

Breast reconstruction following mastectomy: a comparison of submuscular and subcutaneous techniques.

An analysis of the benefits of submuscular versus subcutaneous implantation was made on mastectomy patients. Ninety-one breast were reconstructed following mastectomy. In 30 breasts, the implants were placed subcutaneously; in 19, subpectorally, and in 42, beneath both the pectoralis and the serratus. The follow-up averaged 2 to 3 years, and recent cases included postoperative tonometry measurements to quantitate the degree of capsular contraction. In addition, 12 cadaver dissections were done to delineate muscle insertion and origins. Results indicate that (1) submuscular implants are clearly superior to subcutaneous ones; (2) subpectoral implantation requires complete detachment of the muscular origin from the ribs; (3) subserratus implantation provides extra muscular coverage, but dissection is more difficult owing to its firm rib attachment; and (4) the subserratus technique provided the lowest incidence of capsular contracture, although the breast was slightly flatter initially, but improved with time.

Breast↗
PubMed1981

Recovery, life span, and function of stored plateletpheresis units.

Plateletpheresis units collected using the Haemonetics Model 30 or the IBM 2997 cell separator were stored for 24 h at 22 degrees C. Autologous recovery and life span measurements averaged 64 +/- 13% (1 SD) and 8.9 +/- 1.3 (1 SD) days. The hemostatic effectiveness of these preparations were satisfactory; the corrected increment 4-6 h and 18-24 posttransfusion was 20,400 and 13,400/microliter/m2, respectively, and the bleeding time showed improvement in each patient. There was no significant difference in these parameters between collection devices.

Blood Platelets↗
PubMed1980

Generation of monodisperse fibrous glass aerosols.

Investigations of the aerodynamic behavior of fibers, lung deposition studies which involve fibers and investigations which are concerned with the biological effects of fibers create the need for fibrous aerosols monodisperse with respect to both fiber length and diameter. The method of preparation presented in this paper is primarily based on embedding the bulk quantity of fibers in a plastic histological preparation medium and subsequently cutting the fibers to the desired lengths. The slices which are obtained by the microtoming process are purified of the plastic medium by burning and ashing and the fibrous dust obtained in this manner is then cleared of any debris by liquid elutriation. The results show that gram quantities of nearly monodisperse glass fiber dust with lengths of up to 50 micrometers can be obtained.

Aerosols↗
PubMed1980

Post-transfusion hepatitis: current perspectives.

Viral hepatitis is still the most serious post-transfusion complication. Despite the routine screening of donor blood for the hepatitis type B surface antigen in the United States, post-transfusion hepatitis develops in approximately 7% of blood recipients. Type B hepatitis accounts for only 10% to 15% of cases; non-A, non-B hepatitis constitutes the remainder. Non-A, non-B hepatitis is usually asymptomatic and anicteric but often runs a prolonged course manifested by persistent or intermittent elevations of alanine aminotransferase levels. The risk of developing non-A, non-B hepatitis is increased considerably when blood from paid rather than volunteer donors is transfused. Although there are currently no definitive preventive measures that can be used to reduce the attack rate, the possibility of developing a serologic test fot the non-A, non-B agent is under active investigation.

Blood Donors↗
PubMed1979

Use of plasma products with whole blood and packed RBCs.

During the past five years, there has been a sharp increase in the use of packed RBCs (PRBCs) and plasma products, whereas whole blood (WB) transfusions have steadily decreased. In order to determine whether plasma and its derivatives were being used to "reconstitute" whole blood from PRBCs, we performed a retrospective evaluation of all transfusion episodes in ten representative regional hospitals during a five-month period. Our results indicate that PRBCs were transfused 2.5 times more frequently than WB. Plasma products were administered with PRBCs less often than with WB: 14% of all PRBCs vs 24% of all WB units tranfused. The likelihood of a patient receiving plasma was found to correlate with the total amount of blood transfused and the frequency of transfusion. This study provides evidence that, at most, only a small percentage of PRBCs are given in conjunction with plasma as "reconstituted" WB.

Blood Transfusion↗
PubMed1978

Transmission of hepatitis B virus infection by transfusion of frozen-deglycerolized red blood cells.

Chimpanzees were used to determine the ability of prior freezing of red blood cells to prevent the transmission of Type B post-transfusion hepatitis. Four units of human whole blood were each inoculated with 10(6) infectious doses of hepatitis B virus. Although all units became HBsAg negative after freezing and deglycerolization, hepatitis B virus infection developed in all four chimpanzees when these units were transfused. Two of these chimpanzees had only serologic evidence of infection, including the development of HBsAg and antibody to both the hepatitis B surface and core antigens; in these animals, the incubation periods were prolonged (24 to 25 weeks). In contrast, the other two animals also had elevated serum glutamic pyruvic transaminase (peaks of 190 and 461 IU per liter) and had a more rapid onset. There was no hepatitis B virus infection in two nontransfused controls. Our results do not support the use of frozen red blood cells for the prevention of post-transfusion hepatitis.

Alanine Transaminase↗