Endocytosis of aggregated immunoglobulin G by rat basophilic leukemia cells; rate, extent, and effects on the endocytosis of immunoglobulin E

Rat basophilic leukemia (RBL) cells have distinct receptors for IgE and IgG. We assessed the endocytosis of chemically and immunochemically cross-linked mouse-IgG and its influence on the simultaneous endocytosis of IgE. We found that at 37 degrees C, aggregates of IgG and IgE were endocytosed at about the same rate with one-half of the maximal endocytosis occurring in 5 to 13 min, and the efficiency of endocytosis for both ligands ranging from 40 to 70%. We also found that endocytosis of cross-linked IgE and IgG occurred simultaneously and neither ligand significantly affected the rate or extent of endocytosis of the other. The cells accumulated the cross-linked IgG, and then released it to the extracellular environment, at a rate (less than 3%/hr) slower than the released endocytosed IgE (greater than 10%/hr). Using an assay that discriminates between unbound and receptor-bound oligomeric IgG, we found that oligomeric IgG is endocytosed with its receptor, and that the bulk of the ligand remains bound to its receptor for greater than 120 min after endocytosis. The differences in the rate of release of endocytosed IgG vs IgE suggests that the intracellular fate or pathway of these two oligomeric ligands may differ.     

Calmodulin Acts as an intermediary for the effects of calcium on gap junctions from crayfish lateral axons

Summary Lateral axons from the abdominal nerve cord of cray-fish were internally perfused with the calcium receptor calmodulin (CaM) in solutions with low (pCa>7.0) or high (pCa 5.5) calcium concentrations and studied electrophysiologically and morphologically. Results from these experiments show that when the internal solution contains calcium-activated calmodulin (Ca²⁺-CaM) the junctional resistance between the axons increases from control values of about 60 to 500–600 k in 60 min. In contrast, axons perfused with calmodulin in low calcium solutions maintain their junctional resistance at control levels during the 60-min perfusion. Similar results are obtained when only one or both coupled axons are perfused.The morphological study shows that in the perfused axons the axoplasmic organelles are replaced or grossly perturbed by the perfusion solution up to the region of the synapses. Additionally, in axons perfused with Ca²⁺-CaM there are regions where the synaptic gap between the membranes decreases from a control 4–6 to 2–3 nm. Both electrophysiological and morphological results can be interpreted as indicating that calcium-activated calmodulin acts directly on the junctional channels to induce their closure.     

A further 46,XYp- female

A 24-year-old female with a Swyer syndrome phenotype was found to have a 46,X,del (Y) (p11) karyotype. This observation is consistent with the recently confirmed assignment of the testis-determining master gene to the deletion interval 1A of the Y (Page et al., 1987). Otherwise, it illustrates the etiological heterogeneity of the Swyer phenotype and allows to emphasize the de novo origin of XYp-females.     

Familial inv(2) (p2300q11.2)

A hitherto undescribed inv(2) (p2300q11.2) was found in 2 generations of a family ascertained through a holoprosencephalic liveborn boy with normal karyotype. This inversion, quite probably not related to the child malformations, does not seem neither impair reproductive fitness nor to yield viable recombination aneusomies.     

C-anaphases: a mitotic variant.

In order to assess the frequency of C-anaphases in colchicine-arrested lymphocyte cultures, the authors studied 100 patients classified in four groups: spontaneous abortion (n = 17), subfertility (n = 12), aneuploidy (n = 18) and miscellaneous (n = 53). At least 300 mitotic G-banded cells were scored by individual. In 12 individuals no C-anaphases were observed; in 87 individuals the range was 1-7 with a mode of 2 and a mean of 2.14; the remaining individual had 19 C-anaphases in 330 cells (5.7%). The statistical analysis did not show significant differences between the groups (p > 0.05). These data along with previous studies indicate that normally most individuals have < or = 3% of C-anaphases in habitual lymphocyte cultures. Moreover, there exists an autosomal dominant form in which individuals with the trait have > 5% of the cells with such mitotic configurations. We conclude that both the low frequency common and the high frequency familiar forms are mitotic variants without pathological significance.     

Detection of virulence factors in culturable Escherichia coli isolates from water samples by DNA probes and recovery of toxin-bearing strains in minimal o-nitrophenol-beta-D-galactopyranoside-4-methylumbelliferyl-beta-D-g luc uronide media.

A total of 449 Escherichia coli isolates in treated and raw water sources were submitted to DNA-DNA hybridization using seven different DNA probes to detect homology to sequences that code for Shiga-like toxins I and II; heat-stabile and heat-labile toxins, adherence factors EAF and eae, and the fimbrial antigen of entero-hemorrhagic E. coli. Fifty-nine (13%) of the isolates demonstrated homology with one or more specific DNA probes. More than 50% of the isolates in treated water were not recovered in MMO-4-methylumbelliferyl-beta-D-glucuronide media designed for detection of this indicator.     

Field tests of an acephate baiting system designed for eradicating undesirable honey bees (Hymenoptera: Apidae).

Field evaluations were made of a baiting system designed for use by regulatory agencies in suppressing populations of undesirable feral honey bees, Apis mellifera L. (e.g., bees posing hazards [especially Africanized bees] and colonies infested with parasitic mites). Bees from feral or simulated feral (hived) colonies were lured with honey and Nasonov pheromone components to feeders dispensing sucrose-honey syrup. After 1-3 wk of passive training to feeders, colonies were treated during active foraging by replacing untreated syrup with syrup containing 500 ppm (mg/liter) acephate (Orthene 75 S). In four trials using hived colonies on Grant Terre Island, LA., 21 of 29 colonies foraged actively enough at baits to be treated, and 20 of the 22 treated were destroyed. In the lower Rio Grande Valley of Texas (two trials at each of two trials), treatments killed 11 of 16 colonies (6 of 10 hived; 50 of 6 feral). Overall results showed that all 11 colonies that collected greater than 25 mg acephate died, whereas 3 of 10 colonies receiving less than 25 mg survived. Delivering adequate doses required a minimum of approximately 100 bees per target colony simultaneously collecting treated syrup. The system destroyed target colonies located up to nearly 700 m away from baits. Major factors limiting efficacy were conditions inhibiting foraging at baits (e.g., competing natural nectar sources and temperatures and winds that restricted bee flight).     

Nigericin forms highly stable complexes with lithium and cesium

Nigericin is a monocarboxylic polyether molecule described as a mobile K⁺ ionophore unable to transport Li⁺ and Cs⁺ across natural or artificial membranes. This paper shows that the ion carrier molecule forms complexes of equivalent energy demands with Li⁺, Cs⁺, Na⁺, Rb⁺, and K⁺. This is in accordance with the similar values of the complex stability constants obtained from nigericin with the five alkali metal cations assayed. On the other hand, nigericinalkali metal cation binding isotherms show faster rates for Li⁺ and Cs⁺ than for Na⁺, K⁺, and Rb⁺, in conditions where the carboxylic proton does not dissociate. Furthermore, proton NMR spectra of nigericin-Li⁺ and nigericin-Cs⁺ complexes show wide broadenings, suggesting strong cation interaction with the ionophore; in contrast, the complexes with Na⁺, K⁺, and Rb⁺ show only clear-cut chemical shifts. These latter results support the view that nigericin forms highly stable complexes with Li⁺ and Cs⁺ and contribute to the explanation for the inability of this ionophore to transport the former cations in conditions where it catalyzes a fast transport of K⁺>Rb⁺>Na⁺.Part of the results of this paper were presented at the 14th International Congress of Biochemistry in Prague, Czechoslovakia.