Effect of spleen cell conditioned medium on megakaryocytopoiesis in a short-term bone marrow culture system

The effect of pokeweed mitogen-stimulated spleen cell conditioned medium (PWCM) on the proliferation of megakaryocytes and megakaryocyte progenitor cells (CFU-M) was studied with a short-term liquid culture (STLC) system. Adherent and nonadherent cells were sampled daily for acetylcholinesterase-positive cells and CFU-M. The proliferative capacity of CFU-M was determined by culturing cells from STLC in secondary methylcellulose cultures and counting the number of megakaryocytes per colony. Positive dose-related effects were observed between the number of megakaryocytes and CFU-M in liquid culture and the concentration of PWCM in the culture. In contrast, the proliferative capacity of CFU-M was lower in cultures containing high concentrations of PWCM compared with cultures containing low concentrations of PWCM. Furthermore, mean megakaryocyte diameter was significantly smaller in cultures containing high levels of PWCM compared with cultures with low concentrations. These data suggest that at low levels of conditioned medium, megakaryocytopoiesis is characterized by production of fewer CFU-M with a higher proliferative capacity and fewer large megakaryocytes. In turn, high concentrations of PWCM promote the production of a greater number of CFU-M with reduced proliferative capacity and an increased number of small megakaryocytes.     

The use of liquid nitrogen cryospray for treatment of trichiasis.

Cryosurgical destruction of eyelashes has been successful using a double freez-thaw liquid nitrogen spray technique. While other cryogens are successful in treating trichiasis, they are contraindicated in the treatment of malignant eyelid lesions. If the clinician intends to treat both these entities, it would be simpler to use a liquid nitrogen unit; otherwise, two separate cryosurgical instruments would be required. The liquid nitrogen treatment requires two cycles of a rapid freeze to -15 degrees C coupled with a slow thaw and has given us a 90%+ success rate. Contraindications in treating trichiasis with cryotherapy include paralytic lids and heavily pigmented patients. In general, we do not treat trichiasis involving less than one-third of the lid, especially with young, healthy-appearing lid margins.     

Pathogenesis of visna. IV. Spinal fluid studies.

Visna is a persistent retrovirus infection of sheep which produces a chronic progressive paralytic disease after an incubation period lasting from months to years. The cerebrospinal fluid (CSF) was repeatedly sampled in a group of Icelandic sheep which were infected intracerebrally and followed up to 42 months. Minimal levels of infectious virus were isolated from the cerebrospinal fluid (CSF) up to 4 months after infection after which CSF neutralizing antibodies appeared in many sheep. These antibodies varied in titer and in some animals exceeded serum antibody levels which were moderate to high. CSF antibody is apparently produced within the CNS by local proliferation of B cell clones, and is accompanied by the appearance of considerable numbers of plasma cells in the neural parenchyma. Some sheep raised serum antibody to a second serotype of visna virus and in a number of these animals heterotypic antibody was also found in the CSF. An increase in CSF leukocytes often occurs within 1 to 3 months following infection and may then persist or wane. A persistent high level of CSF cells is an indicator of progressive CNS disease and such animals are more likely to yield virus, have higher CSF antibody levels, more severe CNS lesions, and an enhanced risk of clinical illness (progressive paralysis). CSF cells are predominantly macrophages and lymphocytes, with a consistent minority of plasma cells.     

Metastatic medullary thyroid carcinoma. Complete response to combination chemotherapy with dacarbazine and 5-fluorouracil

A 20-year-old woman had a sporadic case of medullary thyroid carcinoma (MTC) metastatic to the lungs. After a transient response to streptozotocin and doxorubicin, new subcutaneous lesions appeared on the left chest wall and there was progression of pulmonary disease. Because MTC is one of the amine precursor uptake and decarboxylation (APUD) tumors, treatment was undertaken with agents active in these diseases. Dacarbazine and 5-fluorouracil, given daily for 5 days every 4 weeks, resulted in complete resolution of pulmonary and subcutaneous lesions and a sharp decrease in tumor marker levels that lasted 10 months. Recurrence of the pulmonary disease lead to her death 21 months after presentation. Thus, the chemo-responsiveness of MTC may be akin to that of other APUD carcinomas (APUDomas) and treatment of metastatic MTC and other APUDomas with the combination of dacarbazine and 5-fluorouracil appears to merit further study.