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Biomedical subjects

C Bauer

Publications and source records attributed to C Bauer.

At least 379 records · Page 21Linked to original sources
PubMed1978

Net charge and oxygen affinity of human hemoglobin are independent of hemoglobin concentration.

The dependence of net charge and oxygen affinity of human hemoglobin upon hemoglobin concentration was reinvestigated. In contrast to earlier reports from various laboratories, both functional properties of hemoglobin were found to be independent of hemoglobin concentration. Two findings indicate a concentration-independent net charge of carbonmonoxy hemoglobin at pH 6.6: (A) The pH value of a given carbonmonoty hemoglobin solution remains constant at 6.6 when the hemoglobin concentration is raised from 10 to 40 g/dl, indicating that there is no change in protonation of titratable groups of hemoglobin: (b) the net charge of carbonmonoxy hemoglobin as estimated from the Donnan distribution of 22Na+ shows no dependence on hemoglobin concentration in this concentration range. The oxygen affinity of human hemoglobin was determined from measurements of oxygen concentrations in equilibrated samples using a Lex-O2-Con apparatus (Lexington Instruments, Waltham, Mass.). P50 averaged 11.4 mm Hg at 37 degrees C, pH = 7.2, and ionic strength approximately 0.15. Neither P50 nor Hill's n showed any variation with hemoglobin concentrations increasing from 10 to 40 g/dl.

Electrophysiology↗
PubMed1978

[The interaction between phosphate and protein, and the respiration of the llama, the human fetus and the horse (author's transl)].

The sequence analysis of llama (Lama glama, Camelidae) hemoglobin is described. The chains were separated, cleaved by trypsin as previously described, quantitatively characterized and sequenced in the sequenator. The llama hemoglobin differs from the human hemoglobin in that it has 25 different amino acids in the alpha chain and 24 different amino acids in the beta chain. The interaction between protein and phosphate is discussed. The earlier finding that the O2 affinity of the llama hemoglobin is dependent on its content of 2, 3-bisphosphoglycerate is interpreted here as a mutation of the 2, 3-bisphosphoglycerate contact position beta2 His in human hemoglobin to beta2 Asn in llama hemoglobin, whereby one of the four 2, 3-bisphosphoglycerate contact points is interrupted. This interruption gives rise to a diminished reduction of intrinsic oxygen affinity in the hemoglobin molecule and explains, on a molecular basis, the increased oxygen affinity of the llama hemoglobin, and consequently, the high-altitude respiration of the llama. By analogy, the increased O2 affinity of human fetal hemoglobin is interpreted according to previous physiological investigations on blood and fetal hemoglobin by the inactivation of the phosphoglycerate contact point beta143 His in the adult hemoglobin by mutation to gamma 143 Ser in the fetal hemoglobin. With respect to respiration in horses (2, 3-bisphosphoglycerate contact beta2 Gln), measurement of atomic parameters show that the amido group of the glutamine is situated close enough to the 2, 3-bisphosphoglycerate oxygen to build a hydrogen bond with the phosphate. Consequently, the explanation of the low-altitude respiration of the horse lies in the fact that glutamine and histidine fulfill sterochemically an identical function.

Animals↗
PubMed1977

Oxygen-linked CO2 binding to isolated beta subunits of human hemoglobin.

It is known that most of the oxygen-linked carbamate which is formed in normal adult human hemoglobin (Hb A) is confined to the beta subunits rather than to the alpha subunits. In order to find out if similar differences exist in the isolated protomers of Hb A we have measured the effect of various pressures of carbon dioxide (pCO2) on the oxygen affinity in the following heme pigments: isolated alpha and beta subunits with free --SH groups (alphaSH, betaSH), mercurated beta subunits (betaPMB), myoglobin (Mb), and betaSH/PLP in which the terminal alpha-amino group of betaSH was irreversibly blocked with pyridoxal phosphate (PLP). Similar measurements were done on Hb A and the fraction of oxygen-linked carbamate calculated from the effect of pCO2 (at constant pH) on the oxygen half-saturation pressure (p50). A distinct influence of CO2 on p50 was observed in betaSH which was absent in betaSH/PLP and thus indicates that the terminal alpha-amino group mediates the oxygen-linked binding of CO2 in betaSH as it does in the beta subunits of Hb A. However, the fraction of oxygen-linked carbamate was much less dependent on pH and pCO2 in betaSH than in Hb A. Neither alphaSH, betaPMB, or Mb, all of which are known to exist largely or wholly as monomers but have free terminal alpha-amino groups, showed a shift of p50 upon addition of CO2. As both betaSH and betaSH/PLP were shown to be tetrameric molecules, we conclude from this study that homotetramers composed of isolated beta subunits do exhibit a reciprocal interaction between the binding of O2 and CO2.

Adult↗
PubMed1977

Causes of high blood O2 affinity of animals living at high altitude.

We have measured the partial pressure of O2 at 50% saturation (P50) and the concentration of various phosphate compounds in the erythrocytes of the bar-headed goose and the guanaco to establish the cause of the high blood O2 affinity in animals who normally reside at high altitude. The same data were obtained in the blood of two goose species, that live at sea level, and in human blood. At standard conditions (pH 7.4, PCO2 40 Torr, 37 degrees C), P50 was 29.7 Torr in the blood of the bar-headed goose and was about 10 Torr higher in the goose species living at sea level. Since the concentration of organic phosphates was not markedly different in the erythrocytes of either goose species we conclude that the hemoglobin of the bar-headed goose reacts more weakly with organic phosphates, which can also be inferred from studies on purified hemoglobin solutions. Likewise, the low P50 of guanaco blood in comparison with human blood can be explained by a reduced interaction of 2,3-bisphosphoglycerate of guanaco hemoglobin compared to the human pigment.

Adenosine Triphosphate↗
PubMed1977

[Regulation of respiration at high altitudes and its molecular interpretation: the sequence of beta-chains of hemoglobins from pig and llama (author's transl)].

The primary structures of the beta-chains from pig (Suidae) and llama (Lama glama, Camelidae) hemoglobins are given. They differ from human beta-chains in the exchange of 22 and 23 amino acid residues, respectively. Some aspects of the sequences are discussed and the molecular interpretation of respiration at high altitudes is given. This interpretation is based on the exchange of the 2,3-diphosphoglycerate contact beta2His leads to Asn from man to llama: the interaction between the heterotropic allosteric effector 2,3-diphosphoglycerate and protein is diminished, which results in higher oxygen affinity of the hemoglobin of llama. Thus the placental respiration and the high-altitudes respiration have the same molecular mechanism.

Altitude↗
PubMed1976

Evaluation of the genetic effects induced by vinyl chloride monomer (VCM) under mammalian metabolic activation: studies in vitro and in vivo.

As part of a programme of investigations on the biological effects of the industrial compound vinyl chloride monomer (VCM), the raw material for the production of polyvinyl chloride (PVC), analyses on the genetic effects by this compound have been done by experiments (in vitro) which have taken mammalian metabolism into account. Vinyl chloride in the presence of purified microsomes (sedimented at 105,000 g) obtained from mouse liver was converted into an active metabolite(s) which produced gene mutations in the yeast Schizosaccharomyces pombe (forward mutation) and gene conversions in two loci of a diploid Saccharomyces cerevisiae. Moreover, the compound was active in the host-mediated assay, when mice were treated with an oral dose of 700 mg/kg. The role is discussed of mutagenicity tests for the prediction of both genetic and carcinogenic risks of chemical compounds in industrial use.

Animals↗
PubMed1976

The ductus debate: ligation in prematurity?

This report describes 20 premature infants who have undergone surgical ligation of a patent ductus arteriosus (PDA), diagnosed solely by physical examination in all but 2 instances. There were no operative deaths. Eleven of these 20 infants had severe associated hyaline membrane disease (HMD) necessitating mechanical ventilatory support from the first or second day of life. Only 3 of these 11 infants (27%) ultimately survived to leave the hospital. In contrast, 8 of 9 premature meonates (89%) with severe congestive heart failure but without HMD were discharged alive. Surgical ligation of the PDA in a premature infant is an appropriate and successful mode of treatment when congestive heart failure is refractory to medical management. Proof is lacking, however, to establish the efficacy of PDA ligation in the premature infant with HMD.

Cardiac Catheterization↗
PubMed1976

Neonatal jaundice--a comparison between intravenous oxytocin and oral prostaglandin E2.

The total serum bilirubin levels at two and occasionally five days after birth were studied in 162 infants whose mothers received either intravenous oxytocin or oral Prostaglandin te2 during labour, and the results were compared with those obtained in forty-two control patients. Following labour of spontaneous onset, whether the mother received intravenous oxytocin or oral Prostaglandin E2, neonatal total serum bilirubin levels were not different from those in controls. After induction by amniotomy and an active agent, higher mean total serum bilirubin levels were found in infants whose mothers received intravenous oxytocin than in those given oral prostaglandin E2; a significant rise in the total serum bilirubin level appeared to occur when mothers received a total of more than 12,000 milliunits of oxytocin or more than 4,000 milliunits per kg birthweight of the infant.

Female↗