[Trans-corneal trabeculectomy]

One of the main causes in failure of fistulizing operations for glaucoma is related to conjunctival and subconjunctival cicatrization. Trans-corneal trabeculectomy is different from conventional fistulizing operations and the conjunctival incision is avoided. Passing through the cornea, partial thickness sclera and trabecula are removed. The conjunctiva is least violated during the procedures. Trans-corneal trabeculectomy was completed in 15 eyes with glaucoma. Most of filtering blebs revealed diffuse. The conjunctival inflammatory reaction was minimal with only mild hyperemia even at the first postoperative day. Intraocular pressure of 14 eyes was normal without any medication postoperatively.

[An evaluation of fibronectin and IgG in bronchoalveolar lavage fluid of patients with interstitial lung diseases]

FN and IgG levels in both bronchoalveolar lavage fluid and peripheral blood were evaluated in 25 patients with ILD and in 11 normal controls. The results showed: (1) In normal group, the level of lavage fluid FN was similar to that of plasma (P > 0.05). FN levels in BALF of patients with ILD were not only significantly higher than those of controls, but also than those of their own plasma (P < 0.01). However, plasma FN levels showed no remarkable changes in all study groups. (2) IgG levels were significantly increased in BALF of patients with ILD and were somewhat elevated in serum. (3) There were significant correlations between lavage FN or IgG levels and total cell counts in ILD, lavage FN and percentage of neutrophils in IPF, and lavage FN or IgG and percentage of lymphocytes in non-IPF. (4) A highly significant correlation existed between FN and IgG levels in BALF of patients with ILD. These data suggested that FN is significantly increased in patients with ILD. Elevation of lavage FN in ILD may be served as a marker of activity in assessment of alveolitis and elevation of lavage IgG appears to reflect an aspect of activity of humoral immunologic reaction in patients with ILD.

c-k-ras and p53 mutations occur very early in adenocarcinoma of the lung

The topographical distribution of a mutation provides insight into past patterns of tumor evolution. This approach was applied to two loci commonly mutated in adenocarcinoma of the lung--p53 and c-K-ras. In 41 primary adenocarcinomas, c-K-ras codon 12 point mutations were detected in 8 (19.5%) tumors and p53 point mutations were detected in 10 (24.4%) tumors, with one tumor harboring both mutations. These mutations were only detected in malignant cells and with a homogeneous topographical distribution throughout 16 tumors, including metastasis. Intratumor heterogeneity was detected in only one tumor in which a small portion lacked the specific p53 mutation. Based on this topographical analysis, it is likely that when these mutations occur in adenocarcinoma of the lung, they are usually acquired during the very earliest phases of tumor formation before the bulk of clonal expansion, and in very small precursor lesions.

High efficiency retroviral mediated gene transduction into single isolated immature and replatable CD34(3+) hematopoietic stem/progenitor cells from human umbilical cord blood

Umbilical cord blood is rich in hematopoietic stem and progenitor cells and has recently been used successfully in the clinic as an alternative source of engrafting and marrow repopulating cells. With the likelihood that cord blood stem/progenitor cells will be used for gene therapy to correct genetic disorders, we evaluated if a TK-neo gene could be directly transduced in a stable manner into single isolated subsets of purified immature hematopoietic cells that demonstrate self-renewed ability as estimated by colony replating capacity. Sorted CD34(3+) cells from cord blood were prestimulated with erythropoietin (Epo), steel factor (SLF), interleukin (IL)-3, and granulocyte-macrophage colony stimulating factor (GM-CSF) and transduced with the gene in two ways. CD34(3+) cells were incubated with retroviral-containing supernatant from TK-neo vector-producing cells, washed, and plated directly or resorted as CD34(3+) cells into single wells containing a single cell or 10 cells. Alternatively, CD34(3+) cells were sorted as a single cell/well and then incubated with viral supernatant. These cells were cultured with Epo, SLF, IL-3, and GM-CSF +/- G418. The TK-neo gene was introduced at very high efficiency into low numbers of or isolated single purified CD34(3+) immature hematopoietic cells without stromal cells as a source of virus or accessory cells. Proviral integration was detected in primary G418-resistant(R) colonies derived from single immature hematopoietic cells, and in cells from replated colonies derived from G418R-colony forming unit-granulocyte erythroid macrophage megakaryocyte (CFU-GEMM) and -high proliferative potential colony forming cells (HPP-CFC). This demonstrates stable expression of the transduced gene into single purified stem/progenitor cells with replating capacity, results that should be applicable for future clinical studies that may utilize selected subsets of stem/progenitor cells for gene therapy.

Genetic heterogeneity of the c-K-ras locus in colorectal adenomas but not in adenocarcinomas

BACKGROUND

Previous molecular genetics studies of colorectal cancer have identified multiple mutations in the c-K-ras gene (also known as KRAS2) in all phases of its development. Because of technical difficulty, prior studies rarely focused attention on the detailed distribution of c-K-ras mutations in multiple regions of the same primary tumor specimen. However, with recent development of the selective UV radiation fractionation method, characterization of c-K-ras mutations in multiple regions of the same primary tumor specimen can be performed.

PURPOSE

Our purpose was to describe how c-K-ras mutations were distributed among cells obtained from multiple regions of the same primary tumor in an attempt to describe differences between early and late colorectal carcinogenesis.

METHODS

Formalin-fixed, paraffin-embedded tissue blocks were obtained. Seven adenocarcinomas and seven adenomas were selected for the presence of mutant c-K-ras genes and histologic transitions between normal and neoplastic tissue. Tissue sections were prepared for analysis by the selective UV radiation fractionation method by placing thin, fixed tissue sections on a plastic slide with no coverslip. Under the microscope, small ink dots from a felt-tip pen were manually placed directly on relatively pure cell subpopulations. The slides were placed with the tissue side exposed to a UV transilluminator for 2-4 hours to inactivate the DNA present in the unprotected ("undotted") cells. Individual dots were cut out of the plastic slide into 2 x 2-mm squares and placed into microfuge tubes. The DNA was extracted and supernatant used for polymerase chain reaction (PCR) analysis. Mutations at c-K-ras codons 12 and 13 were detected.

RESULTS

The selective UV radiation fractionation method and PCR analysis revealed that c-K-ras mutations never extended into normal mucosa and were present in all neoplastic cells regardless of phenotypes in all seven adenocarcinomas and three of the seven adenomas. Further examination of two carcinomas for p53 (also known as TP53) mutations or loss of heterozygosity demonstrated that these additional mutations were also present in all tumor cells, suggesting that a single transformed clone was responsible for the majority of growth. However, in four other adenomas, tumor heterogeneity was demonstrated, since c-K-ras mutations were detected only in discrete portions.

CONCLUSIONS

Adenoma formation may include a stage in which multiple and genetically distinct neoplastic clones are present, while most carcinomas appear to have a homogeneous composition that may result from the successful progression of one of these clones.

Bicyclic compounds as ring-constrained inhibitors of protein-tyrosine kinase p56lck

A study was undertaken to prepare inhibitors of the lymphocyte protein-tyrosine kinase p56lck. Using the known p56lck inhibitor 3,4-dihydroxy-alpha-cyanocinnamamide (4) as a lead compound, bicyclic analogues were designed as conformationally constrained mimetics in which the phenyl ring and vinyl side chain of the cinnamamide are locked into a coplanar orientation. Such planarity was rationalized to be an important determinant for binding within a putative flat, cleftlike catalytic cavity. Bicyclic analogues were prepared using the naphthalene, quinoline, isoquinoline, and 2-iminochromene ring systems and examined for their ability to inhibit autophosphorylation of immunopurified p56lck. The most potent analogues were methyl 7,8-dihydroxyisoquinoline-3-carboxylate (12) (IC50 = 0.2 microM) and 7,8-dihydroxyisoquinoline-3-carboxamide (13) (IC50 = 0.5 microM). Inhibition by 12 was not competitive with respect to ATP. These compounds may represent important new structural motifs for the development of p56lck inhibitors.

[Changes in interleukin-1 released by pulmonary alveolar macrophage in patients with interstitial lung disease]

To evaluate the activity of PAM, levels of IL-1 released by PAM in patients with ILD (non smokers) were measured using lipopolysaccharide (LPS) stimulation and thymocyte proliferation method, healthy non-smokers as control group. The results showed that IL-1 released by PAM in patient groups both with and without LPS stimulation were significantly higher than that in control group, and also IL-1 released by PAM in healthy smokers was significantly higher than that in health non-smokers. It was indicated that IL-1 might play an important role in the process of ILD and chronic pulmonary inflammation.

Adipocytes of old rats produce a decreased amount of differentiation factor for preadipocytes derived from adipose tissue islets

Adipose tissue of young rats (3.5 mo) contains cell formations ("islets") that, in culture, give rise to a variety of preadipocytes, or islet-derived cells (IDCs), that undergo rapid morphologic differentiation into adipocytes. Such adipose conversion depends on a differentiation-promoting factor produced by the mature adipocytes also present in the cultures. Here we report that cultured IDCs from epididymal fat of senescent rats (20 +/- 3 mo) show decreased adipose conversion compared to IDCs from 3.5 mo rats at 3 days of culture (14.2% vs 29.9%; p < .001). Both the number of co-cultured adipocytes and increased fragility with age were excluded as having a substantial role in explaining the decreased conversion. In order to determine whether the decrease differentiation of the IDCs of the old rats was intrinsic or due to reduced production of the differentiation factor by the old adipocytes, cross-over cultures of IDCs from young and old rats were grown in the presence of young or old adipocytes. When IDCs of old rats were cultured in the presence of young adipocytes, a significant twofold increase in differentiation was seen compared to old IDCs grown with old adipocytes (22.7% vs 10.3%; p < .001). This response was comparable to that of young IDCs grown with young adipocytes. Thus, old IDCs retain their ability to undergo extensive morphologic differentiation when appropriately stimulated. Reduced production of the differentiation-promoting factor by old adipocytes rather than the ability of IDCs to differentiate appears to be responsible for the decreased adipose conversion of IDCs seen in cultures of adipose tissue from senescent rats.

Cross-linking of surface immunoglobulin activates src-related tyrosine kinases in WEHI 231 cells

Crosslinking of sIgM on the B cell line WEHI 231 with anti-sIgM antibody induces protein tyrosine phosphorylation, implicating protein tyrosine kinases (PTKs) in sIg-mediated signal transduction. We have analyzed this cell line for members of the src family of PTKs and have evaluated whether these PTKs might be involved in the process of sIgM-mediated signaling. Our results show that Blk, Lyn, Lck, and Hck are detectable in WEHI 231 cells. Addition of antibodies to sIgM were found to variably stimulate the activities of Blk, Lyn, Lck, and Hck as measured by immune-complex protein kinase assays. Autophosphorylation of these src PTKs, as assessed by reaction with anti-phosphotyrosine antibodies, increased over the time course of sIgM-mediated activation. Co-immunoprecipitation studies to investigate the potential physical interaction of src PTKs with the sIgM receptor complex revealed that, under digitonin and Brij 96 lysis conditions Lyn, Lck, Hck, but not Blk associated with sIgM.

Specific genetic analysis of microscopic tissue after selective ultraviolet radiation fractionation and the polymerase chain reaction

A method using selective ultraviolet radiation fractionation followed by polymerase chain reaction (PCR) can analyze specific cell subsets present on a microscope section. Direct ultraviolet radiation of fixed and stained tissue sections prevents subsequent amplification by PCR. An "umbrella" or dot placed physically over small numbers of pure cell populations selected by microscopic examination protects these cells from the ultraviolet inactivation. The DNA in these protected cells can be specifically amplified while no signal is derived from the unprotected surrounding cells. Specific amplification was demonstrated by detecting human papillomavirus sequences only if infected cells were protected. Similarly, loss of heterozygosity at the p53 locus was documented by selective dotting of normal or tumor cells. The method allows the specific and sensitive molecular genetic analysis of small numbers of cells histologically identified and selected under the microscope.

Ecology and prevention of a shellfish-associated hepatitis A epidemic in Shanghai, China

During a shellfish-borne hepatitis A outbreak in Shanghai during the first quarter of 1988, 300,000 cases were reported in two months. Using cell culture and experimental infection of marmosets, hepatitis A virus (HAV) was isolated from clams collected from the market and the sea bed during the epidemic. A dose-response curve correlating the quantity of clams consumed to the attack rate of hepatitis A was well documented. The occurrence of the epidemic was associated with a good harvest of clams in a new area, serious pollution of this area with sewage and importation of the clams in large quantities into Shanghai where most young adults were susceptible. Clams can apparently be decontaminated by using a continuous water flow. In this way, HAV titres can be reduced by 90% in one day and by 99.9% in two weeks. An attenuated live HAV vaccine which has been developed in China has been shown to be safe and immunogenic and may be used for prevention of such epidemics in the future.

[Determination of elastase and alpha 2-macroglobulin in bronchoalveolar lavage fluid in patients with interstitial diseases and its clinical significance]

Determination of elastase and its inhibitor alpha 2-Macroglobulin was done in BALF in 40 patients with ILD (study group) and 10 healthy volunteers (control group). The results showed that BALF levels of elastase and alpha 2-macroglobulin in study group were significantly higher than those in control group (P less than 0.01; P less than 0.05). Correlation was found between BALF elastase levels and cell count (r = 0.3214, P less than 0.05). It was suggested that elastase may play a role in the development of pulmonary fibrosis in interstitial lung diseases.

[Distribution of lectin-receptors in normal, dysplastic and neoplastic cervical epithelium]

112 cases of normal, dysplastic and neoplastic cervical epithelium were studied with a panel of twelve various lectins and ABC technique. The results showed that: (1) ConA and WGA receptors were relative to Squamous epithelial origin of the Cervix. (2) PNA, UEA-1, BSL and PHA receptors correlated with the tumorigenicity of cervical squamous epithelium. (3) WGA receptor correlated with the cell differentiation of squamous carcinomas. (4) DBA receptor was related with tumor invasion. (5) ConA and SJA receptors were related to the tumorigenicity of columnar epithelium of the endocervical glands. (6) Applications of neuraminidase caused compositional changes of glycoconjugates in the receptors of normal, dysplastic and malignant cervical epithelium and this may be of some value in clinical practice.

Analysis of styryl-based inhibitors of the lymphocyte tyrosine protein kinase p56lck

Several styryl-based compounds were evaluated for their capacity to act as inhibitors of the non-receptor tyrosine protein kinase p56lck. Our results demonstrate that alpha-cyanocinnamamide compounds can inhibit both the in vitro tyrosine autophosphorylation of p56lck as well as p56lck phosphorylation of exogenous substrates. Compound 67B-83-A was found to inhibit p56lck protein kinase activity with a calculated IC50 of 7 to 10 microM. This compound did not significantly inhibit the tyrosine protein kinase activity of the epidermal growth factor receptor and was found to be a less effective tyrosine protein kinase inhibitor for other members of the src family of protein kinases.

Dietary alterations of plasma lipoproteins influence their interactions with proteoglycan enriched extracts from neointima of normal and injured aorta of rabbit

The interactions between serum lipoproteins isolated from rabbits fed a cholesterol-supplemented diet for six weeks, and soluble extracts of arterial neointima enriched in proteoglycans extracted from normocholesterolaemic rabbit aortas, were studied in an in vitro system. Neointimal tissues of rabbit aorta, which developed during three months following a selective endothelial injury, were excised and the areas covered or uncovered by regenerated endothelium were separated. To isolate the proteoglycan enriched fraction, both normal and injured tissue was homogenized in a sucrose solution containing protease inhibitors, centrifuged, and further fractionated by gel exclusion chromatography. The composition of the soluble extracts and each of their corresponding proteoglycan enriched fractions were analyzed in terms of protein and glycosaminoglycan content. Lipoproteins of donor animals fed an atherogenic diet were prepared by sequential ultracentrifugal flotation after density adjustment with KBr. Aliquots of electrophoretically pure lipoprotein fractions were incubated with proteoglycan enriched fraction from uninjured, denuded, or endothelium-covered neointima in the presence of Ca++ and Mg++ at 4 degrees C. The complexes formed during incubation were separated by centrifugation. The cholesterol content of the complexes was considered as an index of binding capacity. Results were expressed as micrograms of cholesterol bound per mg of glycosaminoglycan. The data reveal the higher affinity of hypercholesterolaemic lipoprotein fractions for aortic proteoglycans, as compared to normocholesterolaemic lipoproteins. In addition, when evaluating the relevance of the proteoglycan enriched fraction source, the affinity of fractions extracted from aortic neointima was found to be much higher for hypercholesterolaemic lipoproteins. These results suggest the role that proteoglycan-lipoprotein interactions could play in the event of the combined actions of endothelial injury and hypercholesterolaemia in the pathogenesis of atherosclerosis.

On the choice of times for data analysis in group sequential clinical trials

Planned interim analysis of randomized clinical trials has been implemented for over a decade. While the initial proposal advocated analyzing after equal numbers of patients were evaluated, a later modification by Lan and DeMets (1983, Biometrika 70, 659-663) allowed for more flexible boundaries. Rather than fixing the times of analysis at equal numbers of patients, they fixed the rate at which overall alpha was used up according to a use function alpha * (t) on t in with alpha * (0) = 0 and alpha * (1) = alpha. Here we consider how flexible Lan and DeMets' procedure is. We show that the choice of alpha * (t) for a particular trial affects the permissible analysis times if other desirable properties of the sequence of nominal significance levels are to hold. To overcome the difficulties posed by patterns of late analysis, piecewise linear convex use functions are proposed.

Islets of preadipocytes highly committed to differentiation in cultures of adherent rat adipocytes. Light- and electron-microscopic observations

Cultures of adherent mature adipocytes, obtained from collagenase-digests of adipose tissue of the rat, invariably contain rapidly proliferating, fibroblast-like cells despite the washing and centrifugation procedures employed during isolation of the fat cells. Such spindle-like cells originate from low-density structures, which we term "islets", that are present, together with the mature adipocytes, in the floating layer of the digest of adipose tissue. Islets are found in preparations from adult (3-4 months old) as well as aging (17-24 months old) rats. By light- and electron microscopy, the islets appear as clusters of closely associated cells containing a variable amount of lipid-like material. Cells of endothelial or pericytic origin are also present in the islets. Within a few hours of culture, the islets give rise to those spindle-like cells that have been seen to proliferate in the cultures. By 36-48 hours, such cells begin to accumulate lipid droplets and, by 150 hours, assume the morphology of small mature adipocytes (diameter 20-35 microns) with a large central lipid droplet. The pattern of differentiation of these cells recalls that of preadipocytes derived from the stromal-vascular fraction of adipose tissue digests. Nonetheless, the extent and rapidity of their adipose conversion, as well as the culture conditions necessary for differentiation, are different and suggest that these cells are a substantially uniform subpopulation of adipocyte-precursor cells highly committed to differentiation.

Phosphonate-containing inhibitors of tyrosine-specific protein kinases

Tyrosine-specific protein kinases (TPK) are important signal transducing enzymes involved in normal cellular growth and differentiation and have been implicated in the etiology of a number of human neoplastic processes. Efforts to develop agents which inhibit the function of these enzymes by interfering with the binding of substrate have been limited by the lack of detailed three-dimensional structural data. Many inhibitors of substrate binding share a common styrene nucleus 1 which has been postulated to function as a conformationally constrained analogue of tyrosine. In an effort to develop high-affinity compounds based on this hypothesis, a number of derivatives were synthesized in which either methylphosphonate (4a-c) or (hydroxymethyl)phosphonate (3a-c) were appended to the aromatic 4-position of styrene-containing moieties. The intent of this approach was to prepare hydrolytically stable analogues which expressed additional enzyme recognition features present during the phosphorylation of tyrosine itself. None of the analogues showed inhibitory activity up to the maximum concentration tested (1000 microM) when assayed against autophosphorylation of A-431-derived epidermal growth factor receptor (EGFR) or p56lck (autophosphorylation and transphosphorylation of rabbit muscle enolase). Additionally, a series of naphthalene-based inhibitors including (1-naphthalenylhydroxymethyl)phosphonic acid (14), its known 2-positional isomer 16, and sulfonate (19, 20) and phosphate derivatives (17, 18) were also tested under similar conditions. Only (2-naphthalenyl-hydroxymethyl)phosphonic acid (16) showed activity (IC50 = 250 microM in EGFR, in agreement with the reported literature value). These results suggest that the interaction of styrene-based inhibitors with the substrate binding domain of TPKS may not occur in a manner analogous to the interaction of tyrosine with this domain.

[Studies on the influence of air cavities during irradiation with high energy electrons]

Radiation therapy of tumors is often performed with high energy electrons. In certain situations air cavities in the irradiation volume can change the dose distribution. The effects of air cavities on the dose distribution are investigated. The results calculated with a therapy planning system and measured in a phantom are described and compared with one another and with the literature.

X-ray diffraction studies on the absolute configuration of alpha- and beta-anordrins

The molecular structures and absolute configurations of alpha- and beta-anordrins are reported. Pure alpha- and beta-epimers were obtained with recrystallization and column chromatography combined with high-pressure liquid chromatography methods; they were identified by high-resolution infrared and mass spectra and 1H and 13C nuclear magnetic resonance. By single crystal x-ray diffraction analysis, the crystals of alpha- and beta-epimers were found to belong to the orthorhombic space groups P2(1)2(1)2(1) and P2(1)2(1)2, respectively. The molecular structures of these two epimers were determined. The absolute configurations were deduced by conformation analysis, 1H nuclear magnetic resonance, and comparison with the absolute configuration of the starting material. The absolute configurations of asymmetric centers of alpha- and beta-epimers were observed to be 2R, 5S, 8R, 9S, 10S, 13S, 14S, 17R, and 2S, 5S, 8R, 9S, 10S, 13S, 14S, 17R, respectively. These results were confirmed by the x-ray diffraction determination of the absolute configuration of 2 alpha,17 alpha-diethynyl-A-nor-5 alpha- androstane-2 beta, 17 beta-diol dichloroacetate.

Adipose tissue islets: tissue culture of a potential source of fat cells in the adult rat

Collagenase digests of adipose tissue of the 3 to 4-month-old rat contain groups of 20-100 tightly arranged cells (islets) that copurify with the free-floating fat cells. When cultured along with mature adipocytes the islets give rise to cells, initially fibroblast-like, which rapidly proliferate, acquire lipid droplets, and differentiate into small adipocytes within 4-6 days without the addition to the medium of the agents usually required to produce differentiation in stromal-vascular preadipocytes. Differentiation of these cells is independent of confluence and begins as early as day 2 of culture. The proportion of islet-derived cells that differentiate is directly correlated with the number of mature adipocytes simultaneously present in the culture (r = .709; P less than 0.001). Culture medium exposed to mature adipocytes demonstrated differentiation-promoting activity, suggesting a paracrine effect of these cells. Islets may in vivo constitute a source for newly formed adipocytes in the adult rat. The differentiation of these potential adipocytes may be regulated, at least in part, by the mature fat cells via a paracrine effect.

[Cytological examination of bronchoalveolar lavage fluid and its clinical significance in patients with diffuse interstitial lung diseases]

Cytological examination of bronchoalveolar lavage fluid (BALF) was carried out in 48 patients with diffuse interstitial lung diseases based on chest roentgenography. 7 cases manifested with respiratory symptoms but without any abnormality on both chest roentgenogram and fibroptic bronchoscopy served as controls. The total cell counts of BALF in the study group were all higher than those of the control group (3.1 x 10(5)/ml) and the differential count of the cells showed that neutrophilic granulocytes was found in patients with fibrosing alveolitis, Neutrophilic granulocytes accounted for 21.3 +/- 2.4% of all the cells and the percentage was significantly higher than that of the control group (1.8 +/- 0.5% P less than 0.01). On the contrary, lymphocytosis was found in patients with allergic alveolitis and sarcoidosis; lymphocytes accounted for 30.8 +/- 5.3% and 29.0 +/- 1.1% of all the cells in these two diseases respectively and the percentage was also higher than that of the control group (3.0 +/- 0.6% P less than 0.01). However, the differential cell count of BALF in alveolar carcinoma showed no significant difference with that of the control group (P greater than 0.05). The factors influencing the quality control of both BAL and cytological examination were evaluated and the clinical significance of these results was discussed.

Preadipocyte stimulating factor in rat serum: evidence for a discrete 63 kDa protein that promotes cell differentiation of rat preadipocytes in primary cultures

In primary cultures of rat preadipocytes (PA) isolated from epididymal or perirenal depots, rat serum is more effective than other animal sera (fetal calf, newborn calf, human, horse, rabbit, cat, sheep, goat, dog, pig) in promoting adipogenic conversion, biochemical differentiation, and mitogenesis. Only mouse serum is comparable to rat serum. This activity is attributable to a specific growth factor (preadipocyte stimulating factor, PSF). An assay for PSF in rat serum was devised using PA from perirenal fat of 3-month-old Fischer 344 rats grown first to confluence in FCS for 8 days and then for the next 3 days in test serum, followed by measurement of triglyceride (TG) and glycerol-3-phosphate dehydrogenase (GPDH). Rat serum induces dose-dependent rapid cell division, which coincides with accumulation of TG and increase of GPDH; for routine quantitation, TG is assayed. The biochemical characteristics of PSF in serum are as follows: stable at 4 degrees C for up to 1 year; inactivated at 100 degrees C (80% loss, 30 min) but stable at 56 degrees C for 1 hr; stable at pH 2-12; non-dialyzable; completely resistant to pepsin, trypsin, and chymotrypsin but destroyed by pronase and subtilisn; stable to DTT and periodate; and m.w. between 68 kDa (Sephacryl-300) and 58 kDa (Sephacryl-300 in 5 M urea). PSF activity is greater in serum from Wistar than from Fischer 344 rats, while activity of serum from Zucker obese (fa/fa) rats is at least as great as that from Wistar rats and, like serum of rats made obese by feeding a high-fat, high-carbohydrate diet, is not suppressed. PSF activity is not due to insulin, insulin-like growth factor-1 (IGF-1), growth hormone, glucocorticoids, or combinations of these hormones. PSF activity was not seen with a number of growth factors including colony-stimulating factor (CSF-1), GM-CSF, interleukins 1, 2, and 3, neuroleukin, tumor necrosis factor, and others. PSF is distinct from the low molecular weight (4-8 kDa) differentiation factor present in rat serum, FCS, and human serum that promotes the adipogenic conversion and cellular differentiation of 3T3-L1, 3T3-F442A, and Ob17 cells. PSF appears to be a new differentiation factor for rat preadipocytes, has properties suggestive of a highly glycosylated protein, and may be highly species specific.