Ultrastructure of Deoxyribonucleic Acid-Membrane Associations in Escherichia coli

Areas of contact between deoxyribonucleic acid (DNA) and intracytoplasmic membrane are frequently seen in the “extra” membrane-forming strain Escherichia coli 0111a₁. By examination of serial sections, it has been estimated that these DNA-membrane associations occur in at least 60% of the extra membrane-containing cells. Most of the DNA masses contained only one contact area. Several cells in which the DNA had been stretched revealed individual fibers connecting to the membrane, suggesting a firm attachment of DNA to membrane. The areas of membrane associated with DNA fibers were usually between 100 and 500 nm in diameter, although some smaller areas were seen. Electron microscopic autoradiography of cells in which the replication forks were labeled showed grains over 24% of the profiles containing a contact area, whereas there were grains over only 16% of the profiles without a contact area. Data from autoradiographs of cells in which the label was “chased” away from the replication fork showed the reverse labeling pattern. These data indicate that the areas of contact between DNA and intracytoplasmic membranes seen in electron micrographs contain the DNA replication forks.     

Anti-kinetochore antibodies: use as probes for inactive centromeres.

Application of a modified immunofluorescence technique using an anti-kinetochore serum enables cytogeneticists to obtain quality metaphase spreads and to localize kinetochores. In a patient with a 45, XX, -9, -11, tdic (9p;11p) constitution, we found that the dicentric marker chromosome has an intensely fluorescent kinetochore (no. 11), the functional centromere, and a less intensely fluorescent kinetochore (no. 9), the inactive centromere. The data suggest that in the process of tandem fusion (telomere-telomere between 11p and 9p), the centromere of chromosome 9 was not deleted, but, rather, inactivated.     

Isolation and partial characterization of bovine gingival AB collagen

Summary Limited proteolysis with pepsin solubilized 25% of the insoluble gingival matrix as mainly soluble collagenous material. Fractional salt precipication at neutral pH resulted in the separation of types III and I at 1.8 and 2.6 M NaCl, respectively. In addition, a collagenous fraction accounting for 2% of the solubilized collagen and precipitating at 4.5 M NaCl was shown to be identical with type V collagen. Isolation and partial characterization of the constituent-α-chains of the 4.5 M PPT by gel filtration, ion exchange and hydroxylapatite chromatography as well as disc electrophoresis showed that gingival type V collagen contains αA and αB chains in a ratio αB/αA of 1.73–1.8. Electron microscopic examination of ATP-precipitates showed that this collagen type gave only one kind of SLS aggregates with asymmetric band pattern characteristically different from that of type I collagen. The data provide evidence that gingival AB collagen is a heteropolymer in which the αA and αB chains are assembled in the same macromolecule in a 1∶2 ratio.     

Detection and discovery of crustacean parasites in blue crabs (Callinectes sapidus) by using 18S rRNA gene-targeted denaturing high-performance liquid chromatography

Recently, we described a novel denaturing high-performance liquid chromatography (DHPLC) approach useful for initial detection and identification of crustacean parasites. Because this approach utilizes general primers targeted to conserved regions of the 18S rRNA gene, a priori genetic sequence information on eukaryotic parasites is not required. This distinction provides a significant advantage over specifically targeted PCR assays that do not allow for the detection of unknown or unsuspected parasites. However, initial field evaluations of the DHPLC assay suggested that because of PCR-biased amplification of dominant host genes it was not possible to detect relatively rare parasite genes in infected crab tissue. Here, we describe the use of a peptide nucleic acid (PNA) PCR hybridization blocking probe in association with DHPLC (PNA-PCR DHPLC) to overcome inherent PCR bias associated with amplification of rare target genes by use of generic primers. This approach was utilized to detect infection of blue crabs (Callinectes sapidus) by the parasitic dinoflagellate Hematodinium sp. Evaluation of 76 crabs caught in Wassaw Sound, GA, indicated a 97% correspondence between detection of the parasite by use of a specific PCR diagnostic assay and that by use of PNA-PCR DHPLC. During these studies, we discovered one crab with an association with a previously undescribed protist symbiont. Phylogenetic analysis of the amplified symbiont 18S rRNA gene indicated that it is most closely related to the free-living kinetoplastid parasite Procryptobia sorokini. To our knowledge, this is the first report of this parasite group in a decapod crab and of this organism exhibiting a presumably parasitic life history.     

The effects of sialoadenectomy and exogenous EGF on taste bud morphology and maintenance

Taste buds on the dorsal tongue surface are continually bathedin saliva rich in epidermal growth factor (EGF). In the followingexperiment, taste bud number and morphology were monitored followingsubmandibular and sublingual salivary gland removal (sialoadenectomy),to determine if EGF plays a role in the maintenance and formationof taste buds. Adult male rats were divided into four groups:sialoadenectomized (SX, n = 4); sialoadenectomized with EGFreplacement (SX + EGF, n = 5); sham-operated (SH, n = 4); andsham-operated with exogenous EGF (SH + EGF, n = 5). After a3 week recovery, SX + EGF and SH + EGF animals were given 50µg/day EGF in their drinking water for 14 days. At day14, saliva was collected, the animals were killed and the presenceof EGF determined by radioligand-binding assay. Tongues wereremoved and histologically examined for the presence and morphologyof taste buds on fungiform and circumvallate papillae, or immunostainedfor the presence of EGF, TGF     

The isolation of Vibrio parahaemolyticus and related vibrios from moribund aquarium lobsters.

Vibrios were isolated in pure culture from the hemolymph of 7 out of 28 dead or dying aquarium lobsters which had been acclimated to 20-22 degrees C. One isolate was identified as Vibrio parahaemolyticus, one as a related marine Vibrio (probably V. marinus), and five as Vibrio alginolyticus. No isolates of halophilic Vibrio species were made from healthy lobsters using thiosulfate citrate bile salts sucrose agar (TCBS).     

Anaerobic fecal bacteria of the baboon.

The predominant bacterial genera of baboon feces were enumerated and identified by established procedures. The predominant genera isolated were Lactobacillus, Eubacterium, Streptococcus, and Bacteroides.     

Microtubules and beta cell function: effect of colchicine on microtubules and insulin secretion in vitro by mouse beta cells

A monolayer culture system was developed to study the role of microtubules in insulin secretion. Cultured cells were obtained to study the role of microtubules in insulin secretion. Cultured cells were obtained by enzymatic digestion of pancreases from C57BL-KsJ mice 6-12 wk of age. On day 4 of culture, the medium was changed, control or treatment medium added, and frequent samples were removed for insulin assay. Microtubules and beta cells were identified by indirect immunofluorescence with monospecific antibodies to tubulin and insulin. An extensive microtubule network radiates from the perinuclear region of the beta cell to the plasma membrane. Although alterations in the calcium concentration of the medium did not affect the microtubule pattern, the absence of calcium or glucose in the medium inhibited insulin secretion (P less than 0.001). Optimum insulin release occurred at a calcium concentration of 2.5 mM. Colchicine, in concentrations of 10(-10) M, did not affect the microtubule immunofluorescent pattern, whereas concentrations of 1 and 5 x 10(-7) M decreased the number of microtubules, and microtubules could not be identified in cultures treated with 10(-6) M colchicine for 2 h. After a 2-h preincubation, the prolonged release of insulin at either 2.0 or 4.5 mg/ml of glucose was decreased by 10(-6) M colchicine (P less than 0.02). The immediate release of insulin was similar to that in control plates and occurred in cultures with no identifiable microtubules. Microtubules and insulin secretion were not altered by 10(-6) M lumicolchicine and prolonged insulin secretion recovered 24 h after removal of colchicine. These studies show that the microtubules facilitate sustained secretion of insulin but are not required for the immediate release of the hormone. Alterations in the extracellular calcium concentration which play an essential role in insulin secretion do not alter the microtubule pattern in the beta cell.     

Delayed partial liquid ventilation shows no efficacy in the treatment of smoke inhalation injury in swine.

In an earlier neonatal porcine model of smoke inhalation injury (SII), immediate postinjury application of partial liquid ventilation (PLV) had dramatic beneficial effects on lung compliance, oxygenation, and survival over a 24-h period. To explore the efficacy of PLV following SII, we treated animals at 2 and 6 h after SII and followed them for 72 h. Pigs weighing 8-12 kg were sedated and pharmacologically paralyzed, given a SII, and placed on volume-cycled, pressure-limited ventilation. Animals were randomized to three groups: group I (+SII, no PLV, n = 8), group II (+SII, PLV at 2 h, n = 6), and group III (+SII, PLV at 6 h, n = 7). Ventilatory parameters and arterial blood gasses were obtained at scheduled intervals. The PLV animals (groups II and III) followed a worse course than group I (no PLV); PLV groups had higher peak and mean airway pressures, oxygenation index, and rate-pressure product (a barotrauma index) and lower lung compliance and arterial partial pressure of oxygen-to-inspired oxygen fraction ratio (all P < 0.05). PLV conferred no survival advantage. The reported beneficial effects of PLV with other models of acute lung injury do not appear to extend to the treatment of SII when PLV is instituted in a delayed manner. This study was not able to validate the previously reported beneficial effects of PLV in SII and actually found deleterious effects, perhaps reflecting the predominance of airway over alveolar disease in SII.