In vivo inhibition of megakaryocyte and platelet production by platelet factor 4 in mice.

The in vivo effect of human platelet factor 4 (PF4) on murine megakaryocytopoiesis and thrombopoiesis was studied. Administration of PF4 induced a dose-dependent decrease in the numbers of megakaryocytes and their progenitor cells (CFU-MK), continuing for 1 week after the injection. However, the size of megakaryocytes and their colonies was not changed following PF4 injection. Platelet levels were significantly decreased at days 3-4. The number of CFU-GM was decreased at days 1-2. White blood cells and hemoglobin were unaffected by PF4. These data indicate that PF4 inhibits megakaryocyte and platelet production in vivo by acting on the early stage of megakaryocyte development.     

Reversed-phase chromatographic method for specific determination of glutathione in cultured malignant cells

A chromatographic method for the specific determination of glutathione in malignant cell lines is described. The method is based on the ability of glutathione-S-transferase to specifically and quantitatively conjugate glutathione to 1-chloro-2,4-dinitrobenzene and chromatographic quantitation of the resultant conjugate, dinitrophenyl-S-glutathione, by reversed-phase liquid chromatography. The assay can be performed on 20 000 g supernatants of cell homogenates without acid extraction. 2-Mercaptoethanol, a sulfhydryl compound often used as a thiol-protective agent to preserve enzymatic activities of a number of enzymes, did not interfere with glutathione determination by this method. The dinitrophenyl-S-glutathione isolated from either standard glutathione samples or from cell homogenates was shown to be identical to authentic dinitrophenyl-S-glutathione using mass spectrometry. Recovery of glutathione in standard samples by the current method was identical to that determined using 5,5′-dithiobis(2-nitrobenzoic acid). Exogenous glutathione added to supernatants of cell homogenate in the presence or absence of 2-mercaptoethanol was also completely recovered.     

Proteolytic processing in a non-lysosomal compartment is required for transcytosis of protein-polylysine conjugates in cultured Madin-Darby canine kidney cells

The transcytosis of horseradish peroxidase, as well as its poly(L-lys) and poly(D-lys) thioether conjugates, was investigated in Strain I Madin-Darby canine kidney (MDCK) cell monolayers grown on 0.4 microns pore size polycarbonate membranes in Costar Transwells. The 3 types of HRP had almost identical rates of transport during the first 2 hr of incubation. However, a significant increase of basal-to-apical transport was detected beginning at 3 hr only in Transwells containing the poly(L-lys) conjugate. This increase was inhibited by colchicine (2 microM) and by the Bowman-Birk protease inhibitor (0.1 mg/ml), but not by NH4Cl (10 mM) or chloroquine (0.1 mM). The increase was abolished either by prior trypsinization of the conjugate or by incubation at 4 degrees C. Ultrafiltration studies indicated that the transcytosed poly(L-lys) conjugate was smaller in size than the original conjugate. These results indicate that the conjugate was processed during transcytosis in a non-lysosomal proteolytic compartment, where its poly(L-lys) moiety was selectively degraded, allowing active peroxidase to be released into the apical medium.     

Synthesis of daunosamine-containing disaccharides

Treatment of 2,3,6-trideoxy-1,4-di-O-(p-nitrobenzoyl)-3-(trifluoroacetamido)-l-lyxo-hexopyranose (1) with benzyl 2,3-dideoxy-d-glycero-pentopyranoside and p-toluenesulfonic acid gave a mixture of benzyl 2,3,6-trideoxy-4-O-p-nitrobenzoyl-3- (trifluoroacetamido)-l-lyxo-hexopyranoside (49%) and benzyl 2,3-dideoxy-4-O-[2,3,6-trideoxy-4-O-(p-nitrobenzoyl)-3-(trifluoroacetamido)-α-l-lyxo-hexopyranosyl]-d-glycero-pentopyranoside (4, 20 %). The structure of the disaccharide 4 was confirmed by a detailed, mass-spectrometric analysis in three modes, namely, negative- and positive-ion, chemical ionization, and electron impact. Similar treatment of the bis(p-nitrobenzoate) 1 with ethyl 2,3-dideoxy-d-glycero-pentopyranoside gave the ethyl glycoside and the desired disaccharide, showing that the transglycosylation is not restricted to benzyl glycosides. Removal of the p-nitrobenzoyl and the benzyl groups from 4 gave the disaccharide 2,3-dideoxy-4-O-(2,3,6-trideoxy-3-trifluoroacetamido-α-l-lyxo-hexopyranosyl)-d-glycero-pentopyranose.     

Synthesis of 7-(tetrahydropyran-2-yl)- and 7-(4-acetoxytetrahydropyran-2-yl)-ε-rhodomycinone and 7-(tetrahydropyran-2-yl)-ε-pyrromycinone

The ¹³C.n.m.r spectra of water-soluble and -insoluble glucans synthesized by enzymes isolated from six strains of Streptococcus mutans are interpreted. The glucans are shown to be composed primarily of α(1→3)- and α-(1→6)-linked glucosyl residues, and the relative abundance of each linkage is estimated from peak areas. Treatment of water-insoluble glucans with dextranase is found to result in water-soluble and -insoluble products, the former enriched in α-(1→6)-linkages and the latter in α-(1→3)-linkages. The structural conclusions arrived at by ¹³C-n.m.r. spectroscopy are consistent with data from methylation analysis and ¹H-n.m.r. spectroscopy.     

Study of a possible structural relationship between thymopoietin and the facteur thymique serique

Background peptide chemistry, and the known 49-amino acid sequence of thymopoietin and the known 9-amino acid sequence of the facteur thymique serique (FTS) allowed the concept that Arg⁴⁹ of thymopoietin might be linked to Gln¹ of FTS in a new 58-amino acid peptide in tissue. Cleavage between Arg⁴⁹ and Gln⁵⁰ adjacent to the unique Lys⁴⁸-Arg⁴⁹ moiety could liberate thymopoietin and the [H-Gln¹]-FTS which could cyclize to FTS by the known reaction. In support of, rather than negating, this concept, synthetic FTS and the new dodecapeptide consisting of Val-Lys-Arg linked to the N-terminal of [H-Gln¹]-FTS showed comparable immune stimulating activity, $\text{in vivo}$; both peptides appeared more active than synthetic thymopoietin II.     

Hemoglobin J Cairo: beta 65 (E9) Lys leads to Gln, A new hemoglobin variant discovered in an Egyptian family.

The present report describes clinical, hematological and biochemical studies of a 27-year old Egyptian woman in whom a fast moving Hb variant was found. The abnormal Hb constituted 48% of the total erythrocyte Hb of the propositus and her father. Structural studies demonstrated that in the abnormal Hb lysine beta 65 is replaced by glutamine. The new Hb mutant is designated hemoglobin J Cairo beta 65 (E9) Lys leads to Gln. This substitution results in only a moderate decrease in cooperativity. No evidence of Hb instability was found. A slight anemic state has been observed in the propositus since she reached adolescence.     

The area of discovery ofApanteles glomeratus (Hymenoptera: Braconidae),Pteromalus puparum (Pteromalidae) andBrachymeria regina (Chalcididae)

The areas of discovery ofApanteles glomeratus, Pteromalus puparum andBrachymeria regina were calculated using two different models. Increasing host or parasite density generally resulted in an initial increase followed by a decrease in area of discovery.     

Modeling influenza seasonality in the tropics and subtropics

Climate drivers such as humidity and temperature may play a key role in influenza seasonal transmission dynamics. Such a relationship has been well defined for temperate regions. However, to date no models capable of capturing the diverse seasonal pattern in tropical and subtropical climates exist. In addition, multiple influenza viruses could cocirculate and shape epidemic dynamics. Here we construct seven mechanistic epidemic models to test the effect of two major climate drivers (humidity and temperature) and multi-strain co-circulation on influenza transmission in Hong Kong, an influenza epidemic center located in the subtropics. Based on model fit to long-term influenza surveillance data from 1998 to 2018, we found that a simple model incorporating the effect of both humidity and temperature best recreated the influenza epidemic patterns observed in Hong Kong. The model quantifies a bimodal effect of absolute humidity on influenza transmission where both low and very high humidity levels facilitate transmission quadratically; the model also quantifies the monotonic but nonlinear relationship with temperature. In addition, model results suggest that, at the population level, a shorter immunity period can approximate the co-circulation of influenza virus (sub)types. The basic reproductive number R₀ estimated by the best-fit model is also consistent with laboratory influenza survival and transmission studies under various combinations of humidity and temperature levels. Overall, our study has developed a simple mechanistic model capable of quantifying the impact of climate drivers on influenza transmission in (sub)tropical regions. This model can be applied to improve influenza forecasting in the (sub)tropics in the future.