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Biomedical subjects

R Lindemann

Publications and source records attributed to R Lindemann.

At least 91 records · Page 5Linked to original sources
PubMed1976

Erythropoiesis-inhibiting factor(s) (EIF): methodologic studies.

Erythropoiesis-inhibiting factors (EIF) have been demonstrated in plasma from hypertransfused animals and from polycythemic individuals during periods of hyperoxia, but there is a decided discrepancy in the data published. In the present paper methodologic variations of a bioassay for demonstrating the erythropoiesis-inhibiting factor are discussed. In these studies no inhibitor of erythropoiesis could be demonstrated in plasma from hypoxia-induced polycythemic mice (HPM) on posthypoxic day 5. Injections of RBC or an equal amount of hemolyzed RBC were capable of suppressing the stimulatory effects of ESF, indicating that a red cell constituent may be responsible for the inhibitory effect observed. Transfusion-induced polycythemic mice (TPM) were therefore considered to be less suitable for demonstrating erythropoiesis inhibitors. Our results from testing several doses of a urinary EIF in normal mice, TPM and HPM, indicated that the HPM provided the most sensitive assay system. A similar effect was obtained with hypoxia-induced polycythemic rats. The most marked effect was seen in HPM when the EIF was injected shortly before administering the ESF, while the effect was less pronounced when the EIF was injected 24 hr before or after the ESF.

Animals↗
PubMed1976

Erythropoiesis inhibiting factor(s) (EIF). The specificity and toxicity of urinary EIF studied in vivo and in vitro.

The specificity and toxicity of the urinary erythropoiesis inhibiting factor (EIF) has been tested both in vivo and in vitro. When EIF was given to ESF stimulated erythropoietically suppressed polycythaemic mice and to mice at maximal endogenous erythropoietic stimulation, a reduction of the erythroid bone marrow cells, the erythropoietic 3H-TdR L.I. and the total number of bone marrow cells were observed. No effect was seen on the myelopoietic bone marrow cells. An unspecific toxic effect was unlikely, since addition of EIF did not alter the proliferation of lymphoblastic cells nor change the glucose utilization of bone marrow cells in vitro. Neither did the amount of dead bone marrow cells increase after being incubated with EIF for 72 h. The results indicate that the urinary EIF is a non-toxic, cell specific inhibitor on erythropoiesis.

Animals↗
PubMed1975

Erythropoiesis inhibiting factor(s) in intact and haemolyzed red blood cells.

A previous report have shown that both intact red blood cells (RBC) and an equal number of haemolyzed cells were able to inhibit erythropoiesis on ESF-induced erythropoiesis, suggesting a cell compound to be responsible for the inhibitiory effect. Haeme and haeme compounds have been found to stimulate or inhibit both erythropoiesis and haeme synthesis. The present work presents data on the inhibitory effect of haemolyzed RBC and compounds from intact RBC on erythropoiesis. The inhibiting factor was found to be of a small molecular size and of the same range as a urinary erythorpoiesis inhibiting factor (EIF). The inhibitor did not contain haeme. Both Fe+2 and Fe+3 were tested, showing no reduction of the 59-Fe incorporation into RBC in the test animals. The inhibition could not be due to dilution of the 59-Fe with unlabelled iron from the haemolyzed cells. On the contrary, Fe+3-ions rather stimulated erythropoiesis, probably due to increased amounts of available iron. Haemolysates were prepared from RBC with different amounts of immature cells. With increasing amounts of reticulocytes, a reduction of the inhibitory effect occurred. Also foetal cells showed less inhibition than an equal amount of adult cells. After high speed centrifugation, the inhibitory effect of haemolysates was found in the supernatant, while ghost cells exerted no inhibition. No species differences were found using both exhypoxic polycythaemic mice and rats. An inhibiting factor was liberated into the incubation medium when RBC were incubated for 20 h. No haemolysis occurred during the incubation period. Mature, adult RBC therefore contain a substance which is different from haeme, with a negative feedback on erythropoiesis.

Animals↗
PubMed1975

Amino acid concentrations in plasma and erythrocytes in aregeneratory and haemolytic anaemias.

The concentrations of unbound amino acids in erythrocytes and in plasma from 7 normal individuals, 11 patients with various types of aregeneratory anaemia, and 4 patients with hereditary haemolytic anaemias were determined on a Technicon Amino Acid Analyzer (Perry et al 1970). Most amino acids were normally found in higher concentrations in plasma than intracellularly. Cystine, methionine and trypotophan were almost exclusively present in plasma. Aspartic acid, however, was mainly found in erythrocytes, and glutathione only in erythrocytes. Glutamic acid and ornithine were more concentrated in the cells, while glycine and asparagine showed approximately the same concentrations in erythrocytes as in plasma. In the patients, plasma amino acids showed little deviations from normal, but in the erythrocytes there were striking changes. Erythrocyte glutamic acid concentrations were moderately to markedly elevated in all patients studied, and glycine concentrations in 13 out of 15 patients. In addition, the following amino acids were increased intracellularly in more than one patient: glutamine (8 patients), serine (7), asparagine (5), threonine (4), taurine (3), alanine (2), valine (2), ornithine (2), lysine (2), citrulline (2). Aspartic acid was decreased in erythrocytes from 4 patients with aregeneratory and 1 with haemolytic anaemia.

Adolescent↗
PubMedDate not supplied

Congenital renal tubular dysfunction associated with maternal sniffing of organic solvents.

Two cases of neonatal renal tubular dysfunction and metabolic acidosis due to maternal sniffing of a product containing toluene are reported. Both mothers had been sniffing regularly throughout their pregnancies. The infants were dysmature and had some dysmorphic features. They had hyperchloraemic acidosis and exhibited amino-aciduria. The metabolic changes were however transient. It is suggested that the sniffing of toluene containing solvents during pregnancy may change membrane permeability in both the proximal as well as distal renal tubules and may also enhance liver enzyme activity in the foetus.

Abnormalities, Drug-Induced↗
PubMedDate not supplied

Dental school Special Patient Care Program during 1977-1979 and 1987-1989: comparisons of regional and state disabled populations.

New patients referred to the Special Patient Care Program at UCLA School of Dentistry during the period of 1977-1979 were compared with new patients referred during the period of 1987-1989. Parameters measured were age, gender, geographic distance from the treatment facility, and primary disability. The UCLA profile of disabilities was then compared with local, regional, and state data on disabilities. The mean patient age decreased from 47 years of age in 1977-1979 to 34 years in 1987-1989 while gender distribution remained approximately the same. The distance from patient's residence to the dental treatment facility increased from the 1977-1979 period to the 1987-1989 period with more new patients traveling over 5 miles for treatment. The 1987-1989 special patient care new patient population was highly representative when disability type was compared with a juvenile population (less than 21 years of age) from the five Regional Centers in LA County and the LA County and State of California Department of Developmental Disabilities populations. The patient training base of an undergraduate dental school program for persons with disabilities is representative of the disabled population of LA county and the state of California.

Adult↗