Ultrastructural Analysis of Spermiogenesis in Segregation Distorter Males of DROSOPHILA MELANOGASTER: The Homozygotes

We have studied spermiogenesis at the ultrastructural level in males of genotype SD(NH)-2/SD-72, which are nearly sterile owing to the dysfunction of virtually all of their sperm. Ultrastructural aspects of spermiogenesis in these homozygous SD males are qualitatively similar to those found among dysfunctional sperm produced by heterozygous SD males. In particular, chromatin condensation and/or compaction has been found to be abnormal. However, major quantitative differences have been noted. Most of the dysfunctional sperm in SD(NH)-2/SD-72 males are individualized and coiled. Then, the sperm evidently undergo degeneration, as few mature sperm can be found in the seminal vesicle. The relevance of these findings to the mechanism leading to near sterility in homozygous SD males is discussed.     

A streptomycin-resistant Escherichia coli mutant with ribosomes temperature-sensitive in the suppression of a nonsense codon.

Summary Cell free extracts from a streptomycin-resistant E. coli mutant which is also temperature-sensitive for Q phage were studied for suppression of a nonsense mutation at various temperatures. The streptomycin-resistant ribosomes of the mutant were found to be temperature-sensitive in suppression of an amber mutation in f2 phage coat protein while retaining the ability to synthesize proteins at an elevated temperature (42° C). The restriction of amber suppression at 42° C is assumed to be related to an alteration in the ribosomal protein S12 of the streptomycin-resistant mutant which also causes a change in its electrophoretic mobility.     

Sexual development of patients with isochromosomes for the long arm of the X chromosome

Summary The sexual development of 14 girls with non-mosaic monocentric 46,X,iXq karyotype was studied. Seven out of eight girls were found to have immature secondary sexual characteristics and amenorrhoea, a finding greatly contrasting with that in Triplo-X girls. The relative ineffectiveness of the isochromosome Xq in maintaining fertility may be due to the absence of one short arm, which probably also carries a gonadal determinant. Alternatively, the presence of two inactivation sites on one isochromosome may render the gonadal determinants inactive at an important stage in gonadal development.     

SUCCESSFUL AORTOCORONARY BYPASS SURGERY IN A PATIENT WITH CLASSICAL HEMOPHILIA A

A patient with documented Factor VIII deficiency (classical Hemophilia A) and a history of previous severe intra- and postoperative hemorrhage and transfusion reaction underwent myocardial revascularization for advanced triple vessel coronary artery occlusive disease. The coagulation status was investigated, and a replacement regimen was instituted. The surgical procedure and postoperative course were uneventful.     

Inactivation kinetics and pharmacology distinguish two calcium currents in mouse pancreatic B-cells

Summary Voltage-dependent calcium currents were studied in cultured adult mouse pancreatic B-cells using the whole-cell voltage-clamp technique. When calcium currents were elicited with 10-sec depolarizing command pulses, the time course of inactivation was well fit by the sum of two exponentials. The more rapidlyinactivating component had a time constant of 75±5 msec at 0 mV and displayed both calcium influx- and voltage-dependent inactivation, while the more slowly-inanctivating component had a time constant of 2750±280 msec at 0 mV and inactivated primarily via voltage. The fast component was subject to greater steady-state inactivation at holding potentials between –100 and –40 mV and activated at a lower voltage threshold. This component was also significantly reduced by nimodipine (0.5 m) when a holding potential of –100 mV was used, whereas the slow component was unaffected. In contrast, the slow component was greatly increased by replacing external calcium with barium, while the fast component was unchanged. Cadmium (1–10 m) displayed a voltage-dependent block of calcium currents consistent with a greater effect on the high-threshold, more-slowly inactivating component. Taken together, the data suggest that cultured mouse B-cells, as with other insulin-secreting cells we have studied, possess at least two distinct calcium currents. The physiological significance of two calcium currents having distinct kinetic and steady-state inactivation characteristics for B-cell burst firing and insulin secretion is discussed.     

Purification and characterization of recombinant Pneumocystis carinii thymidylate synthase

Gatalytically active Pneumocystis carinii thymidylate synthase is expressed to the extent of about 4% of the soluble protein in Escherichia coli χ2913 harboring plasmid pUETS-1.8 (U. Edman, J. C. Edman, B. Lundgren, and D. V. Santi, Proc. Natl. Acad. Sci. USA 86, 6503–6507, 1989). Ion-exchange, affinity, hydrophobic, and reactive dye agarose chromatography steps were explored to devise a large-scale purification protocol for P. carinii thymidylate synthase. Sequential DE52, Q-Sepharose, phenyl-Sepharose, and Cibacron Blue F3GA chromatography yielded enzyme that was homogeneous by SDS-PAGE in a yield of over 50%. The sequence of the first 10 amino acid residues of the purified protein was in accord with that predicted from the DNA sequence. Isoelectric focusing gave a pI of 6.2. Kinetic analysis of the purified enzyme revealed that the the K_m values were 4.7 ± 1.3 μM for dUMP and 15.7 ± 4.3 μM for 5,10-methylenetetrahydrofolate, similar to those of many other thymidylate synthases; the κ_cat of the most active preparation was 0.8 s⁻¹. The enzyme is stable for at least 2 months when stored at −80°C in the presence of 40% glycerol, Tris-HCl, and thiol.     

Fusion of Mycoplasma fermentans strain incognitus with T-lymphocytes.

The ability of Mycoplasma fermentans (strain incognitus) to fuse with cultured lymphocytes was investigated and the fusion process was characterized. Fusion was measured using an assay to determine lipid mixing based on the dequenching of the fluorescent probe, octadecylrhodamine (R18), that was incorporated into the mycoplasma cells. Fusion of M. fermentans was detected with both CD4+ (Molt 3) and CD4- (12-E1) cells. The amount of fusion induced was relatively low and ranged from 5-10% with either cell culture. When primary peripheral blood lymphocytes were used the fusion yield was somewhat higher, reaching 12% of the cell population. Similar findings were obtained with fluorescent microscopy analysis suggesting that a predetermined, but unidentified subpopulation of cultured lymphocytes, were being fused. The rate of fusion was temperature dependent. Following a short lag period fusion at 37 degrees C was virtually completed in 60 min. The lymphocytes remained intact throughout the fusion process, as determined by the Trypan blue staining procedure. Fusion was almost completely inhibited by anti-M. fermentans antisera and by pretreatment of M. fermentans cells with proteolytic enzymes, suggesting that a surface-exposed proteinaceous component is involved in the fusion process.     

The synovial lining of the rabbit knee: A scanning electron microscopy study of specimens reinforced structurally with tannic acid

Summary Medial and lateral synovial linings of the rabbit knee, structurally reinforced with tannic acid during fixation, were studied in the scanning electron microscope. Low-resolution micrographs revealed, in both linings, gross architecture of four types: accordion-like, lobe-like, fatty areolar, and flattened areas. In high resolution, both cellular and acellular surfaces were recorded. A novel, bubble-like appearance, of unknown nature and origin, accounted for 70% of both linings. No definite correlation between anatomical location, gross type, or microarchitectural pattern was noted.