Peptic erosion of gastric mucus in the rat

1. The effect of pepsin on the loss of mucus glycoprotein from the gastric epithelial mucus layer was studied in the rat. 2. Pepsin was instilled into the gastric lumen, and luminal contents were subsequently assayed. 3. Glycoprotein loss increased with luminal pepsin, up to a concentration of 1 mg pepsin/ml. 4. Luminal glycoprotein had a molecular size distribution intermediate between subunit, and native mucus glycoprotein of the epithelial mucus layer. 5. Incubation of gastric epithelial scrapings with pepsin demonstrated that insoluble, native mucus glycoprotein was rapidly degraded to soluble glycoprotein of similar molecular size distribution to that found in vivo in the lumen.     

Isolation of a conserved sequence deleted in Duchenne muscular dystrophy patients.

We have isolated a DNA sequence (HIP25) by subtraction- hybridisation which is deleted in a number of Duchenne muscular dystrophy (DMD) patients. HIP25 is conserved in evolution and hybridises to human fetal and adult muscle mRNA. HIP25 is absent in human fetal fibroblast mRNA. Physical mapping data localise this sequence within Xp21 between the breakpoints of X;autosome translocations found in two females suffering from the disease. HIP25 is a candidate exon sequence for the basic defect in DMD boys deleted at this locus.     

The effect of the zone of polarizing activity (ZPA) on the anterior half of the chick wing bud

Removal of the posterior half of the chick wing bud between stages 17-22 results in failure of the anterior distal tissue to survive and differentiate. This observation has been interpreted in terms of a requirement by the anterior half of a factor supplied by the posterior half of the limb containing the zone of polarizing activity (ZPA). This relationship has been tested by grafting ZPA tissue to the posterior surface of the anterior half after posterior half removal. Grafts made proximally on the cut surface did not significantly improve survival and development, nor did the ZPA prevent the expansion of the cell death in the ANZ beyond its normal boundaries into the distal mesenchyme. However, when grafted distally the ZPA inhibited cell death in the apical mesenchyme and caused the anterior mesenchyme to change its normal prospective fate (radius and digit 2). In all these cases, in addition to digit 2, digit 3 and frequently also digit 4 differentiated. The anterior half went on to develop a full set of digits and zeugopod parts in almost 50% of cases, although no skeleton resulting from this regulation of the anterior half had totally size regulated. These results demonstrate a developmental 'rescue' effect by the ZPA, and further support the view that the ZPA has a central and unique function in normal limb bud development, controlling survival and differentiation of the mesenchyme along the anteroposterior axis.     

Zinc nutrition and leaf carbonic anhydrase activity ofEucalyptus maculata seedlings andTrifolium subterraneum

The competitive ability of eight strains ofBradyrhizobium on Vigna was examined. It was found that strains S24, M10, and M11 occupied a greater percent of nodules when introduced as mixed inoculum of two strains. Growth rate of strains did not affect competitive ability of the strains. Two hydrogen-uptake positive (Hup⁺) strains, S24 and M10, were found to be good competitors while another Hup⁺ strain GR4 was not so. Influence of the host in competition was observed in the case of strain GR4.     

Mutations, duplication, and deletion of recombined switch regions suggest a role for DNA replication in the immunoglobulin heavy-chain switch.

The heavy-chain switch from immunoglobulin M (IgM) expression to IgA expression is mediated by a recombination event between segments of DNA called switch regions. The switch regions lie two to six kilobases upstream of the mu and alpha constant region coding segments. Switch recombination to IgA expression results in a recombinant mu-alpha switch region upstream of the expressed alpha constant region gene. We have characterized the products of switch recombination by a lymphoma cell line, I.29. Two sets of molecular clones represent the expected products of simple mu to alpha switches. Five members of a third set of molecular clones share the same recombination site in both the mu and the alpha switch regions, implying that the five molecular clones were derived from a single switch recombination event. Surprisingly, the five clones fall into two sets of sequences, which differ from each other by several point mutations and small deletions. Duplication of switch region sequences are also found in these five molecular clones. An explanation for these data is that switch recombination involves DNA synthesis, which results in nucleotide substitutions, small deletions, and duplications.     

Characterization of a cytoskeletal matrix associated with myelin from rat brain.

Extraction of rat brain myelin in a buffer containing Triton X-100 yielded a soluble fraction and an insoluble residue that was enriched in cytoskeletal elements. Immunoblot analysis of the detergent-soluble fraction and the insoluble cytoskeletal residue showed that all of the tubulin and more than half of the actin were found within the cytoskeletal fraction. The distribution of myelin-specific proteins was also examined, and revealed that 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) I and most of the myelin basic proteins (MBPs) were equally distributed between both fractions. By contrast, the large MBP (21.5 kDa) and CNPase II (50 kDa) were observed to partition almost entirely with the cytoskeletal fraction. Proteolipid protein was found predominantly in the detergent-soluble fraction, as was DM-20 protein. Analysis of the cytoskeletal fraction by sucrose-density-gradient centrifugation demonstrated that a distinct subset of lipids was tightly bound to the cytoskeletal protein residue. The cytoskeleton-associated lipid was considerably enriched in cerebroside and sphingomyelin by comparison with total myelin lipids. These results indicate that a cytoskeletal matrix is associated with multilamellar myelin, and suggest that this structure may play a fundamental role in myelinogenesis.     

ITP in pregnancy: use of the bleeding time as an indicator for treatment

ITP is a relatively common disorder seen in pregnancy. Current recommendations for management of patient with ITP recommend maintaining the platelet count above 50 x 10(9)/L and the bleeding time less than 20 min. It has been well documented that the bleeding time in ITP is disproportionately shortened in many patients relative to the platelet count. We present a prospective study of 24 ITP patients in whom the bleeding time was used as an indicator for therapeutic intervention in pregnancy. Indications for therapy with prednisone and/or intravenous gammaglobulin were the following: significant clinical hemorrhage due to thrombocytopenia; bleeding time of greater than 20 min at the baseline platelet count; for normalization of hemostasis prior to delivery or surgical procedure. Caesarean section was performed only in cases in which there were obstetrical indications for this mode of delivery or when the fetal platelet count (obtained by fetal scalp vein sample) was less than 50 x 10(9)/L. Of 24 patients with ITP, eight had significant thrombocytopenia (platelet count less than 50 x 10(9)/L) throughout pregnancy. Only two patients required prolonged prednisone therapy. Both suffered side effects of chronic prednisone administration. Four patients were treated with prednisone for a short course (10-14 days) at term to improve hemostasis for delivery. One patient was treated with intravenous gammaglobulin at term in an effort to prevent severe neonatal thrombocytopenia. Seven patients required caesarean section; the remaining 17 patients underwent vaginal delivery. Only one minor bleeding complication was seen - a small wound hematoma post caesarean section. In summary, using the bleeding time as an indicator for therapeutic intervention, treatment of ITP in pregnancy can be minimized. Thus, therapy related toxicity can be avoided.