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Biomedical subjects

C Waller

Publications and source records attributed to C Waller.

At least 19 recordsLinked to original sources
PubMed2000

Myocardial perfusion and intracapillary blood volume in rats at rest and with coronary dilatation: MR imaging in vivo with use of a spin-labeling technique.

PURPOSE: To validate a magnetic resonance (MR) imaging technique that is not first pass and that reveals perfusion and regional blood volume (RBV) in the intact rat. MATERIALS AND METHODS: Measurement of perfusion was based on the perfusion-sensitive T1 relaxation after magnetic spin labeling of water protons. RBV was determined from steady-state measurements of T1 before and after administration of an intravascular contrast agent. The colored microsphere technique was used as a reference method for perfusion measurement. RBV and perfusion maps were obtained with the rats at rest and during administration of 3 mg of adenosine phosphate per kilogram of body weight per minute. RESULTS: At MR imaging, perfusion during resting conditions was 3.5 mL/g/min +/- 0.1 (SEM), and RBV was 11.6% +/- 0.6 (SEM). Adenosine phosphate significantly increased perfusion to 4.5 mL/g/min +/- 0.3 (SEM) and decreased mean arterial pressure from 120 mm Hg to 65 mm Hg, which implies a reduction of coronary resistance to 40% of baseline. RBV increased consistently to 23.8% +/- 0.6 (SEM). CONCLUSION: The study results show that quantitative mapping of perfusion and RBV may be performed noninvasively by means of MR imaging in the intact animal. The presented method allows determination of vasodilative and perfusion reserve, which reflects the in vivo regulation of coronary microcirculation for a given stimulus.

Adenosine↗
PubMed1999

Perfusion-corrected mapping of cardiac regional blood volume in rats in vivo.

Measurement of regional blood volume (RBV) in the myocardium in vivo is important for the assessment of tissue viability and function. The method in this work is based on the acquisition of a T(1) map before and after intravascular contrast agent application. It is known that this method is influenced by perfusion that causes an overestimation of RBV values. In order to solve this problem, the new method is proposed which acquires T(1) maps with slice selective inversion pulses. Due to blood flow nonexcited spins enter the detection slice, which leads to an acceleration of the relaxation time. A model that divides tissue into two compartments is adapted to slice selective inversion in order to derive a simple expression for perfusion-corrected RBV. The aim of the study is to demonstrate the feasibility and accuracy of this technique for quantification of RBV in rat myocardium in vivo. RBV maps were obtained for five rats, and the reproducibility was determined by repeating the experiment several times. A mean RBV value of 12.8 +/- 0.7% (v/v) over all animals was obtained in the myocardium. The results were compared with RBV maps obtained with perfusion-sensitive RBV imaging in the same five rats and with first-pass RBV studies. In order to demonstrate the strength of the new method the vasodilator adenosine was administered and alterations in microcirculation were imaged. Magn Reson Med 42:500-506, 1999.

Adenosine↗
PubMed1998

Proline-induced disruption of a transmembrane alpha-helix in its natural environment.

alpha-Helix formation in globular proteins has been studied both theoretically and experimentally for decades, while a lack of both high-resolution structures and suitable experimental techniques has hampered the study of helices in membrane proteins. We have developed a new experimental approach, glycosylation mapping, where the active site of the lumenally exposed endoplasmic reticulum enzyme oligosaccharyl transferase is used as a point of reference against which the position of a transmembrane segment in the membrane can be measured. Here, we report an initial analysis of the helix-breaking properties of proline residues inserted in a transmembrane helix. We find that proline residues can break a transmembrane helix, but only when inserted near the end, and only when the helix is sufficiently long. The glycosylation mapping technique may be generally useful for determining the position of transmembrane helices in the membrane.

Amino Acid Sequence↗
PubMed1998

Quantitative regional blood volume studies in rat myocardium in vivo.

Many pathophysiological processes in the myocardium are in close relation to changes of the regional blood volume and regional myocardial blood flow or perfusion. Only few methods exist to obtain quantitative values for these parameters. Quantitative regional blood volume (RBV) studies in rat myocardium are presented using snapshot fast low angle shot (FLASH) inversion recovery T1 measurements with two different blood pool contrast agents, gadolinium diethylenetriaminopentaacetic acid (Gd-DTPA) albumin and Gd-DTPA polylysine. In contrast to previous attempts, each snapshot FLASH image acquisition was ECG-triggered under breathhold conditions. To measure relaxation times shorter than a heart cycle, each T1 sequence was repeated two times with different delays between inversion pulse and first image acquisition. The experiments were performed on a Bruker Biospec 70/21 using a homogeneous transmitter coil and a circularly polarized surface receiver coil, a special ECG trigger unit, and a respirator that is controlled by the pulse program. Based on a fast exchange model RBVm maps were calculated from the relaxation time maps for different concentrations of the two blood pool contrast agents. A significant dependence of the RBVm values on blood T1 was found. This is in accordance with a model that has been developed recently relating the dependence of RBVm on T1 of blood to perfusion. For Gd-DTPA albumin, the application of the model to the experimental data yields realistic values for RBV and perfusion. The values, which are in accordance with literature data, were obtained at highest contrast agent concentrations i.e., lowest relaxation times of blood (ca. 200 ms).

Albumins↗
PubMed1998

[Quality control of homologous blood collection activities: 5 years' experience].

Quality control (QC) of blood collection activities for transfusion is a regulatory requirement. The authors report on their experience in this field over the past 5 years. In their institution, this QC is based on both the recording and analyzing of predefined data, as well as the search for an active collaboration from each person involved in these activities. QC of medical selection relies on the assessment of several associated criteria: effectiveness of the information given to blood donors for recruitment, preparation of the medical interview and encouragement to perform regular donations; frequency of donors deferred after the medical interview; frequency of biological abnormalities detected at donation; results of the inquiries into the corresponding medical interviews following adverse transfusion reactions. The quantitative and qualitative evaluation of blood collection permits assessment of the quality of the blood collection program, collection procedures and directly derived blood products. Quality assessment of facilities and equipment is also included in this QC. Results have been improving in recent years, especially regarding medical selection. In particular, an increase in the mean donation rate of donors, a decrease in biological abnormalities detected at donation and an absence of adverse transfusion reactions attributed after inquiry to an inadequate medical interview have been noticed. A decrease in both shortage and outdating of labile blood products likewise indicates an improvement of blood collection planning. However, this QC reveals deficiencies in the information given to donors and a lack of analysis of the data specific to first time donors. In order to further improve the efficiency of QC, these results now require comparison with similar data collected on a nation-wide scale.

Anemia↗
PubMed1998

[Feasibility of following up transfused patients].

The aim of this study was to assess the natural history of patients after transfusion and the acceptability of a standardized biological follow-up. In 1995, during 1 month, in 13 French hospitals, a follow-up at 3 and 6 months after blood transfusion was proposed to all blood recipients who had not received any blood transfusion within the past 6 months (eligible patients): screening for red cell antibodies, alanine aminotransferase (ALT) activity and specific viral markers of hepatitis B (hepatitis B surface antigen and antibody to hepatitis virus core antigen), of hepatitis C (antibodies) and of Human Immunodeficiency Virus (antibodies). At the beginning of the study, 296 patients were followed for 6 months. A complete follow-up was available at 3 months for 183 patients (62%), at 6 months for 168 (57%) and after 6 months, 198 patients (67%) have been once followed. Of eligible patients, 76% were alive at six months. After transfusion, the incidence of red cell alloantibodies and elevated ALT concentration were respectively 4% and 17%. At 6 months, one patient had Hepatitis B surface antigen; the responsibility of blood transfusion was excluded. Within the first 24 hours, 68 patients (23%) required another blood transfusion and 42% of units were transfused to patients with malignant disease. Our study quantifies in real conditions the difficulty of a biological follow-up in a transfused population, mostly composed of patients that could not be followed in the hospital where they were transfused.

Adult↗
PubMed1997

[Evaluation of transfusion practice. Surveys for evaluating the practice of nursing care in transfusion medicine in four hospital sites].

In four medical centers, transfusion medicine care practices were evaluated by testing the nursing staff with a list of questions. The anonymous test evaluated the knowledge and transfusion practices, and in one of them the bed-side compatibility control procedure in particular. These tests showed failures in the labeling of tubes during phlebotomy for immuno-hematologic testing, in blood product conservation in the ward, and in bed-side compatibility testing which is not always carried out fully at the bed-side. These results, showed on which topics the teaching program should emphasize so as to improve the quality of blood transfusion in the medical centers according to legal obligations.

Blood Transfusion↗
PubMed1997

[Pilot study of the characteristics of transfused patients and utilized labile blood products].

The aim of this study was to describe blood recipients and blood components transfused during the first 24 hours in 13 French hospitals. We included all blood recipients who had not had any blood transfusion within the past six months. Recipients were screened for red cell alloantibodies, the alanine aminotransferase activity and specific viral markers (hepatitis B and C, Human Immunodeficiency Virus). Eligible patients represented 47% of the all transfused. Among the 371 patients included, 57% were males and 71% were transfused in a surgical unit. Alloantibodies, non specific and specific viral markers were detected in 3%, 19% and 2% respectively. Among the patients included, 42 received 172 autologous units. In total, 1056 allogeneic units (an average of 3 units per patient) were transfused; blood products were leucocyte-depleted (49%) or leucocyte-poor (20%); 54% of red cell units were matched for antigens Rh and Kell. Neoplasms were the most frequently reported disease for which patients were transfused. This study provides baseline blood transfusion information on recipients and blood utilization for a specific period in French hospitals. Following this study, a national study will allow the clarification of the characteristics, for instance the surgical procedures requiring transfusion.

Adolescent↗
PubMed1997

[Analysis of transfusion incident reports filed at 15 blood transfusion centers and health facilities during 17 months. Groupe Receveurs de laSFTS].

The principal result of the development of hemovigilance since 1994 has been the declaration of undesirable effects likely to be due to transfusions of labile blood products. Using the 1,694 cases of undesirable effects registered, it seemed worthwhile to us to analyze the distribution of the signs noticed, their frequency and the types of blood products responsible. This analysis allowed us to observe that the majority of reactions were shivery-feverish (47%) or allergic (24%). Most of them are linked to platelet concentrate transfusions especially simple donor platelets (with a frequency of ten reactions for thousand apheresis platelet concentrates transfused). In this study the frequency of undesirable effects reported is 2 per 1,000 apheresis platelet concentrate transfusions. Further investigations are necessary to determine the physiological mechanisms of these reactions and to estimate the degree to which transfusions are responsible for their occurrence.

Adult↗
PubMed1997

Blood progenitor cell (BPC) mobilization studied in multiple myeloma, solid tumor and non-Hodgkin's lymphoma patients after combination chemotherapy and G-CSF.

For blood progenitor cell (BPC) mobilization, standard-dose VIP chemotherapy consisting of etoposide, ifosfamide and cisplatin has previously shown effective tumor reduction in solid tumor patients and sufficient progenitor cell mobilization for autologous blood cell transplantation. Mobilization chemotherapy regimens in multiple myeloma (MM) predominantly consist of melphalan or cyclophosphamide that induce marked cytopenia and considerable variability of progenitor cell collection. We studied whether in MM (n = 13), BPCs were efficiently and reproducibly mobilized with etoposide (500 mg/m2) and ifosfamide (1500 mg/m2), followed by daily s.c. G-CSF (5 micrograms/kg). In parallel, patients with solid tumors or non-Hodgkin's lymphomas (n = 28) treated with etoposide (500 mg/m2), ifosfamide (1500 mg/m2) and cisplatin (150 mg/m2) and identical dosing of G-CSF were analyzed. Before chemotherapy (day 0), on day 7 after chemotherapy and on days of leukapheresis (day 9-14), leukocyte numbers, mononuclear cells (MNCs), CD34+ cells and coexpression of lineage markers were analyzed. Median blood leukocyte numbers were 28,100/microliters (range, 19,600-40,400) on day 10 in myeloma patients and progressively declined over the next 4 days. In contrast, in solid tumor and lymphoma patients leukocyte numbers constantly increased from a median of 12,400/microliters (range, 6000-22,000) to 30,000/microliters (range, 16,300-63,300) between day 10 and day 13 after chemotherapy. Similar to leukocyte counts, median MNC numbers decreased in myeloma patients with successive leukaphereses, but steadily increased in solid tumor and lymphoma patients over the same period. CD34+ cell numbers in the blood peaked between day 9 and 11 (median: 40/microliters) in myeloma patients and then declined. In the solid tumor and lymphoma group, median CD34+ counts in the blood peaked on day 12 after mobilization chemotherapy (median: 100/microliters). The median CD34+ yield per leukapheresis in the myeloma group was 2.2 x 10(6)/kg (range, 1.5-4.7) on day 10, and fell steadily to 0.95 x 10(6)/kg on day 12, whereas in solid tumor/NHL patients median CD34+ cell yields remained between 3.5 and 3.7 x 10(6)/kg from day 10 to day 12 after mobilization chemotherapy (P < 0.001). To obtain sufficient cell numbers for engraftment a median of 2 (range, 1-3) mobilization chemotherapy cycles were needed in MM compared to 1 (range, 1-10) in solid tumor or lymphoma patients, with a median of 5 (range, 2-8) leukaphereses in MM compared to 1 (range, 1-10) (P < 0.05). Taken together, we found that for patients with MM, VP16 and ifosfamide efficiently and predictably mobilizes progenitor cells into the PB with > or = 3 x 10(6)/kg CD34+ cells collected after one to two mobilization chemotherapy cycles.

Adult↗
PubMed1997

Epoetin alfa facilitates presurgical autologous blood donation in non-anaemic patients scheduled for orthopaedic or cardiovascular surgery.

Patients expected to need at least three units of blood for their elective cardiovascular or orthopaedic surgery, were allocated randomly to receive intravenous (i.v.) Epoetin alfa 600 IU kg-1 (n = 27), 300 IU kg-1 (n = 30) or placebo (n = 23), on days 1, 4 and 7. Provided haemoglobin > or = 11 g dL-1, one unit of blood was collected on days 1, 4, 7, 11 and 14. Iron supplementation was given throughout the study. Surgery was scheduled between days 18 and 21. Significantly more patients treated with Epoetin alfa (100% for 600 IU kg-1; 97% for 300 IU kg-1) were able to donate > or = 4 units of blood compared with placebo (78%) (P = 0.011 and P = 0.032). No significant differences were seen in total patient exposure to homologous blood (7.4%, 3.3% and 17.4%, respectively). Mean red cell volume donated (P = 0.005 for 600 IU kg-1; P = 0.158 for 300 IU kg-1 both vs. placebo) and production (P < 0.001 and P = 0.012, respectively) were dose related. Twenty-four patients became iron deficient. No differences in the incidence of adverse events were seen between the groups.

Blood Donors↗
PubMed1996

[Management of E. coli dependent factorial diseases in weaning piglets].

The most important postweaning factorial diseases are at least partly caused by E. coli. The term postweaning coli complex can be subcategorized into the following manifestations: postweaning diarrhoea, edema disease, postweaning wasting and hemorrhagic gastroenteritis. In the presented study the effect of prophylactic zootechnique alone and zoo- and biotechnique in combination was evaluated during the first weeks postweaning. The results showed that combined zoo- and biotechnique is superior to simple zootechnique regarding food conversion (1.41 kg versus 1.73 kg), average daily weight gain (390 g versus 325 g) and postweaning piglet mortality (3.1% versus 4.9%). It is the opinion of the authors that combined postweaning zoo- and biotechnique should be performed in such pig production units where ETEC and/or SLTEC are present.

Animal Feed↗
PubMed1996

[Practical experiences in the therapy of postweaning edema disease in piglets].

In a field trial 23 weeks old weaned piglets were orally inoculated with E. coli O139 K12 H1. The piglets received the same food and were kept under the same management regime. They were selected randomly into four groups and treated after the first clinical signs of CNS involvement of edema disease as follows during three days: Group 1: received a single daily i.m. application of 4 mg/kg body weight Melperone. Group 2: received a single daily i.m. application of 2 mg/kg body weight Amperozide. Group 3: was treated orally (intranasally) with 2 mg/kg body weight Amphetamin in a single daily application. Group 4: untreated control. The following parameters were evaluated before the begin of the therapy (day 0-4). A: Occurrence of diarrhea in a group B: Food consumption per piglet per day C: Death of piglets per group After the begin of the therapy (day 5-32) D: Death of piglets per group E: Average daily feed intake per piglet The results showed that the Melperone and Amphetamin treatment was superior regarding all examined parameters when compared to Amperozide treatment and to the control group.

Amphetamine↗
PubMed1994

[Platelet concentrates: types, costs and indications].

Platelet transfusion is a widely used form of therapy and a sound knowledge of its basic principles is essential to obtain the required efficacity while assuring optimal security for the patients. Platelet concentrates (PC) may originate from two types of blood donation: whole blood donation or apheresis. In the first case, the platelets are separated in sterile closed systems following withdrawal of blood from group A or O donors. These so-called "standard" PC (SPC) are most often delivered in the form of mixtures constituting the PC from several donations. In the second case, the platelets are separated from the red blood cells in the course of plasmapheresis or cytapheresis. Generally, these apheresis PC originate from a single donor, except in some cases where the PC from two plasmapheresis donations may be combined. The French Blood Authorities have recently recommended an increase in the proportion of apheresis PC (monodonor) with respect to PC mixtures from several donors, essentially in order to further increase the security against viral contamination. At present, PC are not subjected to viral destruction treatment. In recent times, a number of transfusion centres have introduced systematic determination of the platelet count and volume in all PC delivered, thus enabling inscription on the bag label of the total quantity of platelets (active ingredient) contained in the bag (1 unit = 0.5 x 10(11) platelets). This is useful to calculate the index of platelet recovery after transfusion and to detect refractory states.

Blood Platelet Disorders↗
PubMed1993

[Preoperative normovolemic hemodilution using erythropheresis].

Normovolaemic haemodilution was carried out by erythropheresis by the Blood Bank, 24 to 72 yours before surgery, using a plasmapheresis device. A special disposable haemodilution kit was used, with one plasma and three red cell collection bags and CPD as anticoagulant. Plasma was replaced by 4% albumin. One to 4 red cell packs with 75% haematocrit was obtained and stored for 10 days. This technique is indicated for surgery with an expected blood loss between 1,000 and 1,500 ml, or when the patient cannot be included in a preoperative blood donation programme. The contra-indications are the same as those of intentional normovolaemic haemodilution. This technique has been used in 101 patients due to undergo orthopaedic surgery. Compared with standard haemodilution bags, the advantages of this technique are the excellent asepsis of this product, its 10 days storage and high haematocrit, and the absence of anaesthetic drugs within the bags as well. This technique does not interfere with haemodynamic conditions during anaesthesia; it saves time for both anaesthetists and surgeons. In the authors' experience, this technique has in part replaced the more usual technique.

Adolescent↗