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Biomedical subjects

M S Knapp

Publications and source records attributed to M S Knapp.

At least 19 recordsLinked to original sources
PubMed2000

Cloning, expression, and one-step purification of the minimal essential domain of the light chain of botulinum neurotoxin type A.

A truncated but functional form of the botulinum neurotoxin A light chain (Tyr 9-Leu 415) has been cloned into the three bacterial expression vectors, pET 28, pET 30, and PGEX-2T, and produced as fusion proteins. This 406-amino-acid light chain was expressed with 1 six-histidine tag (LC-pET28), 2 six histidine tags and a S-tag (LC-pET30), or a six-histidine tag and a glutathione S-transferase tag (LC-pGEX-2T). The three fusion proteins have been overexpressed in Escherichia coli, purified in a soluble form, and tested for protease activity. All three recombinant proteins were found to have similar enzymatic activity, comparable to the light chain purified from the whole toxin. The LC-pET30 protein was the most soluble and stable of the three fusion proteins, and it could be purified using a one-step affinity chromatography protocol. The purified protein was determined to be 98% pure as assessed by SDS-polyacrylamide gel. This protein has been crystallized and initial X-ray data show that the crystals diffract to 1.8 A.

Botulinum Toxins, Type A↗
PubMed2000

Identification of novel small molecule ligands that bind to tetanus toxin.

Tetanus toxin belongs to a family of clostridial protein neurotoxins for which there are no known antidotes. Another closely related member of this family, botulinum toxin, is being used with increasing frequency by physicians to treat severe muscle disorders. Botulinum toxin has also been produced in large quantities by terrorists for use as a biological weapon. To identify small molecule ligands that might bind to the targeting domain of tetanus and botulinum toxins and to facilitate the design of inhibitors and new reagents for their detection, molecular docking calculations were used to screen a large database of compounds for their potential to bind to the C fragment of tetanus toxin. Eleven of the predicted ligands were assayed by electrospray ionization mass spectrometry (ESI-MS) for binding to the tetanus toxin C fragment, and five ligands (45%) were found to bind to the protein. One of these compounds, doxorubicin, was observed to have strong hydrophobic interactions with the C fragment. To check the ligands for their ability to compete with ganglioside binding, each was also tested using a GT1b liposome assay. Doxorubicin was the only ligand found to competitively bind the tetanus toxin C fragment with an appreciable binding constant (9.4 microM).

Binding Sites↗
PubMed1991

Innovations in managing difficult behaviors.

Caring for people with difficult behaviors is among the greatest challenges for nursing facility providers. This month, Provider looks at successful techniques in caring for people with dementias and other difficult-to-manage behaviors.

Aged↗
PubMed1984

Saline depletion, pre-renal failure and acute renal failure.

The wide range of diseases that can influence the kidney, either directly or indirectly, all influence water and electrolyte balances according to established 'rules'. There is great scope for helping patients by understanding these rules, and also a great potential to do harm by ignoring them. Careful consideration of simple routine data, and an awareness of the limitations of some indexes and ratios in common use, will usually result in an adequate provisional classification of the patient. This can be used to plan therapeutic trials designed to correct metabolic and electrolytic disturbances, and to organize diagnostic procedures that will establish the cause of any intrinsic renal diseases or the cause of obstructions. Earlier and more frequent use of dialysis and related techniques in management is recommended, as is greater attention to the control of blood glucose, nutrition and electrolyte balance. A general recommendation is that corrections of many deficits should not be excessively rapid.

Acute Kidney Injury↗
PubMed1984

Perturbations in the erythroid marrow progenitor cell pools may play a role in the augmentation of HbF by 5-azacytidine.

In vivo observations on the kinetics of F cells and of fetal hemoglobin (HbF) synthesis and in vitro studies of erythroid progenitors, their number, and the gamma-gene expression in their progeny were carried out in baboons (Papio cynocephalus) treated with 5-azacytidine. Maximum effect on the increase of HbF production in vivo was observed only when an expanded erythroid marrow population was present. In these animals, as well as in normal animals, treatment resulted in a significant reduction of the late erythroid progenitor cell pools (erythroid clusters and erythroid colony-forming units, CFU-E) in the marrow. This reduction was more pronounced among those progenitors grown in the absence of added erythropoietin, and it was followed by a rebound a few days after treatment cessation, reflecting the accumulation of regenerating progenitors. An early increase in the in vitro synthesis of HbF in erythroid clusters and CFU-E colonies was observed. This increase was further documented at the cellular level, with immunofluorescent labeling of colonies with monoclonal anti-gamma-globin chain antibodies. In contrast to the findings in late progenitors, the number of erythroid burst-forming unit (BFU-E) colonies and the synthesis of HbF in these colonies was not influenced significantly by 5-azacytidine treatment. It is proposed that the toxic effects of 5-azacytidine on late progenitors, leading to faster mobilization of earlier progenitors to the next more mature compartment, play a role in the in vivo augmentation of HbF synthesis by this drug. This perturbation in the progenitor cell population kinetics and the presumed hypomethylation of the surviving differentiating cells may act synergistically to produce a maximum HbF response after 5-azacytidine treatment.

Anemia↗
PubMed1983

Detection of renal allograft rejection by computer.

A computer program incorporating an adaptation of a statistical method, the multiprocess Kalman filter, was used to detect changes in trends of plasma creatinine and urea concentrations. In 28 recipients of renal allografts a definite deterioration in renal function was identified retrospectively on 32 occasions by an experienced renal physician independently of the statistical analysis. The computer identified 31 of these 32 episodes using creatinine and urea results, and 29 using creatinine alone. Dysfunction was identified by the computer significantly earlier (p less than 0.05) than by the clinician and a median of one day earlier (p less than 0.02) than treatment was actually initiated. The computer identified dysfunction on 11 out of 1259 days when the clinician did not suspect rejection. These 11 episodes may have had a pathological importance, though no clinical diagnosis was made. This computer method is useful for immediate analysis of incoming results and for timing events either prospectively or retrospectively.

Computers↗
PubMed1983

Computing, mathematics, and the nephrologist.

The potential of computing and mathematics to make major contributions to nephrology by making information retrieval and presentation more accurate, more complete, and more rapid and by providing immediate access to computational and graphic facilities is emphasized in this symposium issue. The realization that disordered physiology due to disease may not prevent the course of an illness being described in mathematical terms should encourage physicians, and others interested in pathophysiology, to integrate mathematics and statistics into their thinking and their practice.

Computers↗
PubMed1983

Mathematical and statistical aids to evaluate data from renal patients.

The monitoring of renal patients and the making of many decisions during their management involves consideration of sequences of numerical data. Renal function results after renal transplantation were used as an example of how graphical presentations, simple mathematical transforms, statistical evaluation and adjustments to the data, to take into account other biological and technical sources of error, can all contribute to better understanding. Experience with a statistical technique, the 4-state Kalman filter not often used in the biological sciences, was summarized and its use suggested as a method to quantitate some traditionally subjective decisions about individual patients, for example, the onset of allograft rejection. The method has identified in retrospect and in prospect events after transplantation earlier than did experienced clinicians. Other statistical techniques to set the sensitivity and specificity of monitoring methods, to detect change points and to quantitate rhythmic sequences of clinical data were discussed, with examples, and with increasing access to computers, these can be used more easily by nephrologists, transplant surgeons, and others.

Computers↗
PubMed1983

Medical research council trial of antilymphocyte globulin in renal transplantation. A multicenter randomized double-blind placebo controlled clinical investigation.

A total of 173 patients who received live donor or cadaveric primary or secondary renal transplants at five British hospitals were entered into a randomized double-blind controlled clinical trial of equine antilymphocyte globulin (ALG) administered prophylactically to prevent rejection. The ALG was prepared in the early 1970s and used cultured human lymphoblasts as antigen. Following transplantation all patients were treated with a standard immunosuppressant regimen of steroids and azathioprine and, in addition, were given either 30 mg/kg ALG or placebo daily for 10 days by intravenous infusion. In comparison with more recently produced materials, the ALG employed in this study was of moderate potency in prolonging skin graft survival in monkeys. Primary graft failure occurred in 27 patients (15/86 ALG and 12/87 placebo). At three to five years after transplantation 50 of the remaining patients had died, almost all from diseases relating to their renal condition, and 25 more had suffered complete graft failure. No significant differences were found between patients treated with ALG and placebo in the numbers with functioning grafts during the 3 years following transplantation, in the time between transplantation and the first rejection episode, or in the number of episodes during the first six months after transplantation. This applied whether live or cadaveric grafts were employed. Within the first 6 months of operation, infection was given as a major contributory cause of death in 12 patients treated with ALG and in 5 who received placebo (P greater than 0.1). Infections were also slightly more common during the two weeks following transplantation in those receiving ALG (13/86 ALG, 10/87 placebo). As expected, graft survival was significantly better in patients who received live donor grafts (P = 0.001) and in patients with the least donor-recipient histocompatibility mismatches (P = 0.008). The results of this multicenter trial show no therapeutic benefit to renal graft recipients from the administration of ALG, and suggest that the risks of fatal infection may have been aggravated. Use of such equine ALG in similar dose regimens is therefore, not, justified in renal transplantation, especially if some part of the apparent effects on fatal infections is real. It is stressed that these findings are relevant only to the equine ALG used in this study, which was raised with cultured human lymphoblasts as the antigen, and to ALG prepared in a similar way and of similar potency. It should not be inferred that these results are applicable to ALG prepared in other ways.

Adolescent↗