Augmented water binding and low cellular water content in erythrocytes of camel and camelids

We investigated a link between hemoglobin primary structure, hemoglobin hydrophobicity-hydrophilicity, and erythrocyte water content in various mammalian species. Some hemoglobin molecules, particularly those of the camel and camelids, contain more charged amino acid residues and are more hydrophilic than the hemoglobins of human and a number of other mammalian species. To test the in vivo significance of these alterations of hemoglobin primary structure, we determined the osmotically unresponsive erythrocyte water fractions in mannit solutions of various osmolarities at 4 degreesC. Among the species investigated, the size of the osmotically unresponsive erythrocyte water fraction relates in a positive linear way to hemoglobin hydrophilicity. The extreme low total erythrocyte water content of camel erythrocytes (1.1-1.3 g water/g dry mass) may be explained by a comparatively high osmotically unresponsive erythrocyte water fraction. It is proposed that alterations of hemoglobin sequences of camel and camelids may be the part of a natural selection process aimed at protecting these animals against osmotic dehydration in arid environments.     

Effects of gravity on tracheal mucus transport rates in normal subjects and in patients with cystic fibrosis

A noninvasive, radionuclide imaging technique for measuring the rate of mucus clearance in the trachea (RT), was used to study gravitational effects on mucus clearance in 13 patients with cystic fibrosis (CF), average age 17 years; 7 normal, nonsmoking adults, average age 26 years; and a normal subject who was recovering from an acute upper respiratory tract infection (URTI). In the upright position, nine of the CF patients and the subject with URTI demonstrated abnormal tracheal mucus clearance which approached normal when they were placed in 25 degrees headdown position. The normal subjects and two of the CF patients showed no significant difference in the RT measured in the two positions. The results of the study indicate that the force of gravity can be a major influence on tracheal mucus clearance in CF and URTI subjects. This conclusion supports the use of postural drainage as an effective form of therapy in patients with cystic fibrosis.     

Antibiotic concentrations in ascitic fluid of patients with ascites and bacterial peritonitis

Thirty-six paired specimens of serum and ascitic fluid from 21 patients with peritonitis and ascites, most with sponetaneous bacterial peritonitis and alcoholic cirrhosis, were assayed for antibiotic content. Antibiotics assayed and number of determinations were gentamicin, 14; tobramycin, 7; ampicillin, 5; clindamycin, 3; penicillin G, 2; cephalothin, 2; chloramphenico, 2; and cefazolin, 1. In 31 pared specimens the ascitic fluid antibiotic concentration was about one half or more of the simultaneous serum level and in 17 assays exceeded 90% of the serum level. All antibiotics studied penetrated ascitic fluid equally well. Clinical response to antibiotic therapy was good in 12 of 16 patients with culture-proven bacterial peritonitis. Antibiotic levels in ascitic fluid exceeded the minimal inhibitory concentration of the infecting organisms in all but one patient who responded. Direct intraperitoneal instillation of antibiotics does not appear to be necessary routinely; however, there may be an initial lag of several hours before antibiotic concentrations is ascites achieve therapeutic levels.     

Role of the kidney in regulating plasma immunoreactive beta-melanocyte-stimulating hormone

An analysis of the factors that influence the increase in plasma immunoreactive beta-melanocyte-stimulating hormone (beta-MSH) concentration in chronic renal failure showed that: (a) the increase correlated with the increase in serum creatinine concentrations; (b) beta-MSH was not cleared from the plasma by haemodialysis; (c) beta-MSH concentrations increased with length of time on dialysis and increased further after bilateral nephrectomy but there was no further increase with time; (d) beta-MSH levels decreased to normal after renal transplantation; and (e) beta-MSH was excreted in urine only when plasma levels rose to well above those of chronic renal failure (in Nelson's syndrome). These findings suggest that the kidney regulated plasma beta-MSH by a non-excretory mechanism and is the major site of beta-MSH metabolism.     

The biosynthesis of human hemoglobin A1c. Slow glycosylation of hemoglobin in vivo

Hemoglobin A1c, the most abundant minor hemoglobin component in human erythrocytes, is formed by the condensation of glucose with the N-terminal amino groups of the beta-chains of Hb A. The biosynthesis of this glycosylated hemoglobin was studied in vitro by incubating suspensions of reticulocytes and bone marrow cells with [3H]leucine or 59Fe-bound transferrin. In all experiments, the specific activity of Hb A1c was significantly lower than that of Hb A, suggesting that the formation of Hb A1c is a posttranslational modification. The formation of Hb A1c in vivo was determined in two individuals who were given an infusion of 59Fe-labeled transferrin. As expected, the specific activity of Hb A rose promptly to a maximum during the 1st week and remained nearly constant thereafter. In contrast, the specific activity of Hb A1c and also of Hbs A1a and A1b rose slowly, reaching that of Hb A by about day 60. These results indicate that Hb A1c is slowly formed during the 120-day life-span of the erythrocyte, probably by a nonenzymatic process. Patients with shortened erythrocyte life-span due to hemolysis had markedly decreased levels of Hb A1c.     

Exon scanning for mutation of the NF2 gene in schwannomas

Family studies and tumor analyses have combined to indicate that neurofibromatosis 2 (NF2), a disorder characterized by multiple benign tumors of the nervous system, and sporadic non-inherited forms of the same tumor types are both caused by inactivation of a tumor suppressor gene located in 22q12. Recently, the gene encoding merlin, a novel member of a family of cytoskeleton-associated proteins, was identified as the NF2 tumor suppressor. To facilitate the search for merlin mutations, we have defined the exon-intron boundaries for all 17 NF2 exons, including one subject to alternative splicing. We have developed polymerase chain reaction assays to amplify each exon from genomic DNA, and used these assays to perform single-strand conformation polymorphism analysis of DNA from 30 sporadic and eight NF2-derived schwannomas, the hallmark tumor type in this disorder. Of a maximum of 60 alleles scanned, 32 showed mutations affecting expression of the merlin protein. Thirty of these mutations are predicted to lead to a truncated protein due to frameshift, creation of a stop codon, or interference with normal splicing, while two are missense mutations. Thus, inactivation of merlin is a common feature underlying both inherited and sporadic forms of schwannoma.     

Studies on Carbohydrate Metabolising Enzymes. Part XXVIII. Preparation and some Properties of α-Amylase Isoenzymes from Malted Rye

α-Amylase was prepared from an extract of malted rye flour by heat treatment to inactivate β-amylase and other contaminating carbohydrases, followed by continuous electrophoresis. This yielded two isoenzymes which differed considerably in physical properties, although their action patterns appeared to be similar. These findings have been compared with the results of studies on α-amylase isoenzymes from other sources.