Effector mechanisms in allograft rejection. IV. In contrast to late cytotoxic cells, and early killer cells infiltrating mouse sponge matrix allografts are predominantly T lymphocytes.

We have earlier demonstrated that a mixed population of immunologically specific killer cells, including cytotoxic T lymphocytes, non-T (“B”) lymphocytes and monocytes, infiltrate “sponge matrix” allografts at the peak of rejection on Day 8 after transplantation. We have now performed a sequential study covering both early and late stages of the rejection response. We demonstrate that the early infiltrating killer cells are sensitive to anti-Ø and anti-T cell serum plus complement treatment but the late killer cells are not. This finding indicates that the first cytotoxic host cells infiltrating the allograft are predominantly T lymphocytes, whereas as the rejection process proceeds also cytotoxic non-T (“B”) lymphocytes and monocytes are recruited to the site of inflammation.     

Immune complex effects on murine macrophages. I. Immune complexes suppress interferon-gamma induction of Ia expression

We have studied the effects of immune complexes on the expression of macrophage surface proteins in vitro. Increased expression of the H-2 molecules I-A, I-E, and K on the macrophage membrane was induced by in vitro culture with crude lymphokine or interferon-gamma. Expression of all three of the molecules was additionally increased by stimulating the cultures with heat-killed Listeria monocytogenes. Addition of soluble immune complexes to the cultures did not have any effect on macrophage expression of these proteins. However, significant inhibition of lymphokine or interferon-gamma induction of I-A, I-E, and H-2K was observed when macrophages were cultured on plates to which immune complexes had been bound. This inhibition was dose dependent, required an immunoglobulin (Ig) molecule with an intact Fc portion, did not require the presence of T cells, and occurred in the presence of indomethacin. Complexes containing IgG1, IgG2a, IgG2b, and IgE, but not IgM or IgA, antibodies mediated the inhibitory effect.     

The protective effects of MSC‐EXO against pulmonary hypertension through regulating Wnt5a/BMP signalling pathway

The aim of the study was to explore the mechanism of mesenchymal stem cell‐derived exosomes (MSC‐EXO) to protect against experimentally induced pulmonary hypertension (PH). Monocrotaline (MCT)‐induced rat model of PH was successfully established by a single intraperitoneal injection of 50 mg/kg MCT, 3 weeks later the animals were treated with MSC‐EXO via tail vein injection. Post‐operation, our results showed that MSC‐EXO could significantly reduce right ventricular systolic pressure (RVSP) and the right ventricular hypertrophy index, attenuate pulmonary vascular remodelling and lung fibrosis in vivo. In vitro experiment, the hypoxia models of pulmonary artery endothelial cell (PAEC) and pulmonary vascular smooth muscle cell (PASMC) were used. We found that the expression levels of Wnt5a, Wnt11, BMPR2, BMP4 and BMP9 were increased, but β‐catenin, cyclin D1 and TGF‐β1 were decreased in MSC‐EXO group as compared with MCT or hypoxia group in vivo or vitro. However, these increased could be blocked when cells were transfected with Wnt5a siRNA in vitro. Taken together, these results suggested that the mechanism of MSC‐EXO to prevent PH vascular remodelling may be via regulation of Wnt5a/BMP signalling pathway.     

Measurement of positional isotope exchange rates in enzyme-catalyzed reactions by fast atom bombardment mass spectrometry: application to argininosuccinate synthetase

Fast atom bombardment mass spectrometry (FAB-MS) has been used to measure positional isotope exchange rates in enzyme-catalyzed reactions. The technique has been applied to the reactions catalyzed by acetyl-CoA synthetase and argininosuccinate synthetase. The FAB technique is also able to quantitatively determine the oxygen-18 or oxygen-17 content of nucleotides on as little as 10 nmol of material with no prior derivatization. Acetyl-CoA synthetase has been shown by FAB-MS to catalyze the positional exchange of an oxygen-18 of ATP from the beta-nonbridge position to the alpha beta-bridge position in the presence of acetate. These results are consistent with acetyl adenylate as a reactive intermediate in this reaction. Argininosuccinate synthetase was shown not to catalyze a positional isotope exchange reaction designed to test for the formation of citrulline adenylate as a reactive intermediate. Argininosuccinate synthetase was also found not to catalyze the transfer of oxygen-18 from [ureido-18O]citrulline to the alpha-phosphorus of ATP in the absence of added aspartate. This experiment was designed to test for the transient formation of carbodiimide as a reactive intermediate. These results suggest that either argininosuccinate synthetase does not catalyze the formation of citrulline adenylate or the enzyme is able to completely suppress the rotation of the phosphoryl groups of PPi.     

Cyclic AMP suppresses expression of v-rasH oncogene linked to the mouse mammary tumor virus promoter

Clone 433.3 of NIH 3T3 cells is a stable carrier of the MMTV LTR:v-rasH chimeric DNA. Only in the presence of dexamethasone (a synthetic glucocorticoid), 433.3 cells exhibit an induced level of p21 transforming protein and phenotypic transformation. N6,O2'-dibutyryl cAMP (DBcAMP) antagonized the effect of dexamethasone in a time - and concentration - dependent manner. DBcAMP (5 X 10(-4)M) added 18 hr prior to the addition of dexamethasone (10(-7)M) almost completely blocked the hormone effect: cells contained levels of p21 20% of that in the cells treated with dexamethasone alone, and formed flat, contact inhibited monolayers. On the basis of these results together with our previous data on mammary carcinomas in vivo, we postulate that cAMP may be an intracellular suppressor acting at a regulatory locus of both cellular and viral ras genes.     

Cyclic AMP-like effects of polyamines on phosphatidylcholine synthesis and protein phosphorylation in human promyelocytic leukemia HL60 cells. Comparison with the effects of phorbol ester

Spermine or putrescine increased cAMP levels through a catalase-sensitive mechanism, resulting in, most notably, a dephosphorylation of protein A (Mr 45,000, pI 5.15) and protein B (Mr 45,000, pI 4.9) and slightly increased phosphatidylcholine (PC) synthesis in HL60 cells. Exogenous dibutyryl cAMP mimicked the polyamine effects. 12-O-Tetradecanoyl phorbol-13-acetate (TPA) also promoted the protein dephosphorylation and PC synthesis, the effects augmented by R59022 and mimicked by exogenous 1-oleoyl-2-acetylglycerol. The effects of spermine (or dibutyryl cAMP) and TPA on PC synthesis were synergistic. It was suggested that cAMP-dependent protein kinase and protein kinase C might mediate, in an independent but inter-related manner, the effects of polyamines and TPA.     

Rectus abdominis myocutaneous free-flap reconstruction following a cranio-orbital-maxillary resection for neurofibrosarcoma

An unusual case of neurofibrosarcoma of the cranio-orbital-maxillary region was resected by a combined neurosurgical and plastic surgical team. The resulting defect was reconstructed in one stage with a free rectus abdominis myocutaneous flap, obviating the need for subsequent prosthetic obturation of the maxillary defect. This reconstructive technique expedited the patient's convalescent period, allowing him to return to work 3 weeks following surgery. Wound healing was uneventful, and the cosmetic result was acceptable to the patient.