Influence of humoral control peptides on medullary vasomotor control neurons: microstimulation and double-labeling studies using SHR and WKY rats

To study the influence of humoral control peptides on medullary vasomotor control neurons, angiotensin II (AII), arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) were microinjected into three vasomotor control areas, i.e., the area postrema (AP), the nucleus tractus solitarii (NTS) and the rostral ventrolateral medulla (RVLM), of spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY), and the evoked cardiovascular response was observed. Unlike the injection areas, the threshold dose of one peptide for the cardiovascular response was similar, but the threshold dose differed from peptide to peptide. The threshold dose was lower for AII (0.15-0.29 pmol), in-between for ANP (0.9-1.5 pmol) and higher for AVP (14-30 pmol). No significant difference in the threshold dose was observed between SHR and WKY, suggesting that hypertension in SHR may not be due to the abnormal sensitivity to the three peptides of the vasomotor control neurons in the AP, NTS, and RVLM. The structural basis of the results of the microstimulation experiment was supported by the double-labeling study. The NTS neurons were innervated by (1) the AII-immunoreactive (ir) neurons in both sides of the lateral hypothalamic area (LH), the RVLM and the caudal ventrolateral medulla, and (2) the ANP-ir neurons in both sides of the paraventricular nucleus (Pa) and the LH. The RVLM neurons were innervated by (1) the AII-ir neurons in both sides of the LH and ipsilateral side of the lateral parabrachial nucleus (Pbl) and (2) the ANP-ir neurons in the ipsilateral Pbl. There was no evidence that the AVP-ir neurons in the Pa and the supraoptic nucleus innervate the NTS and the RVLM neurons, or that the AII, ANP or AVP-ir neurons innervate the AP neurons. This study suggests that in common with SHR and WKY rats AII and ANP may influence both the NTS and RVLM not by the humoral pathway but by the neural pathway, and AVP may not influence the three vasomotor control areas by the neural pathway.

Recognition of rotavirus antigens by mouse L3T4-positive T helper cells

A lymphocyte proliferation assay was used to examine the helper T cell response to rotavirus in mice following parenteral immunization with the UK strain of bovine rotavirus. Mixed populations of lymphocytes prepared from spleen or peripheral lymph nodes were tested for proliferation in the presence of UK strain rotaviruses, prepared as cell culture lysates, ultracentrifuged (pelleted) lysates, sucrose-purified virus and caesium chloride-purified virus. Live rotavirus induced non-specific stimulation of lymphocytes, which was not observed in response to inactivated virus. Putative helper T cells of the L3T4+ phenotype were prepared as an enriched population from UK strain-immunized mice or grown in vitro as a polyclonal T cell line. The response of L3T4(+)-enriched cells from mice immunized with inactivated virus was dependent on antigen-presenting cells (APCs). Cells obtained following immunization with live virus did not require further addition of APCs. The response of the L3T4+ T cell line was wholly dependent on APCs. UK strain-specific L3T4+ cells responded to whole UK rotavirus and to isolated VP6 of both UK and C486 rotavirus strains. The results indicate that virus-specific L3T4+ T cells are induced following rotavirus immunization and can respond to epitopes on VP6. UK strain-primed L3T4+ cells also responded to an avian rotavirus strain, Ch2, which shares only minimal serological cross-reactivity with the UK strain. T cell recognition of rotavirus may thus be broadly cross-reactive.

Cell cycle expression and p53 regulation of the cyclin-dependent kinase inhibitor p21

In normal human fibroblast cells, the primary cell cycle regulators, the cyclin-dependent kinases (CDKs), exist predominantly in multiple quaternary complexes, each consisting of a CDK, a cyclin, proliferating cell nuclear antigen (PCNA) and p21. p21 encodes a universal inhibitor of cyclin-dependent kinases. Here we show that the level of p21 mRNA and the interaction of p21 protein with cyclin-CDK enzymes are regulated during the cell cycle. When normal human fibroblast IMR90 cells were released from serum starvation, p21 mRNA reached its highest level immediately following serum stimulation, began to decrease at the G1/S boundary, fell to its lowest level during S phase, and accumulated again as cells exited from S phase. p21 protein associates with each cyclin-CDK complex in a cell cycle dependent manner. Cyclin A-CDK2-p21-PCNA and Cyclin B1-CDC2-p21-PCNA complexes are assembled in early S and G2 phase, respectively, indicating that p21 and/or PCNA regulates the enzymatic activity of each kinase at the time of their functioning. Cyclin D1-CDK4-p21-PCNA complexes, on the other hand, persist throughout the cell cycle, suggesting that cyclin D1-CDK4 quaternary complexes may play a role in monitoring an event(s) that may occur at any time, rather than at a specific stage of the cell cycle. The level of p21 mRNA in early passage Li-Fraumeni cells that are heterozygous for p53 mutation remained similar to that in normal fibroblasts, but was undetectable in immortalized Li-Fraumeni cells homozygous for mutant p53. This finding provides a plausible molecular explanation for the loss of genetic stability associated with cells homozygous, but not heterozygous, for p53 mutation.

Repression of cyclin D1: a novel function of MYC

Constitutive expression of human MYC represses mRNA levels of cyclin D1 in proliferating BALB/c-3T3 fibroblasts. We expressed a series of mutant alleles of MYC and found that downregulation of cyclin D1 is distinct from previously described properties of MYC. In particular, we found that association with Max is not required for repression of cyclin D1 by MYC in vivo. Conversely, the integrity of a small amino-terminal region (amino acids 92 to 106) of MYC is critical for repression of cyclin D1 but dispensable for transformation of established RAT1A cells. Runoff transcription assays showed that repression occurs at the level of transcription initiation. We cloned the promoter of the gene for human cyclin D1 and found that it lacks a canonical TATA element. Transcription starts at an initiator element similar to that of the adenovirus major late promoter; this element can be directly bound by USF in vitro. Expression of MYC represses the cyclin D1 promoter via core promoter elements and antagonizes USF-mediated transactivation. Taken together, our data define a new pathway for gene regulation by MYC and show that the cyclin D1 gene is a target gene for repression by MYC.

Neuronal expression of Fos protein in the paraventricular nucleus of the hypothalamus after i.p. injection of ulcergenic cinchophen

The purpose of this study was to identify the CNS neurons that express Fos protein after i.p. injection of ulcergenic drug cinchophen (300 mg/kg). This was done in unanesthetized Wistar rats with careful physiological controls. The population of Fos-immunoreactive (Fos-ir) neurons was the largest in the medial parvicellular part of the paraventricular nucleus of the hypothalamus (PVH). Distribution of Fos-ir neurons in the PVH corresponds with that of the parvicellular neurons in the PVH which secrete corticotropin-releasing hormone (CRH). This study strongly suggests that the cinchophen-induced peptic ulcer may originate in excitation of the CRH-secreting neurons in the parvicellular part of the PVH.

Regulation of fos-lacZ fusion gene expression in primary mouse epidermal keratinocytes isolated from transgenic mice

The expression of a fos-lacZ fusion gene was studied in primary mouse epidermal keratinocytes obtained from transgenic mice. This gene construct contains the entire upstream regulatory sequence of c-fos, and expression of the endogenous and fusion gene was shown by Northern analysis to correlate upon induction with the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA). Using a chromogenic substrate of beta-galactosidase, we also demonstrated that expression of the fusion gene product, like that of Fos, was localized to the cell nucleus. In addition, we showed that epidermal keratinocytes responded to dialysed fetal bovine serum (FBS), TPA and high-calcium medium with enhanced Fos-lacZ expression and an inhibition of proliferation. The time course of induction of Fos-lacZ expression was similar for dialysed FBS and TPA, with a peak approximately 2 h after exposure. Exposure for approximately 24 h to an elevated extracellular calcium concentration was required to elicit an increase in Fos-lacZ expression. The lack of an immediate effect of raising medium calcium levels on Fos-lacZ expression contrasted with the rapidity of its effect on DNA synthesis, which was significantly inhibited within 6-8 h. In addition, we found that the protein kinase C inhibitor Ro 31-7549 blocked Fos-lacZ expression induced by TPA but had little or no effect on that elicited by high calcium levels. Thus, although our results indicate that the fos gene product may be involved in mediating epidermal keratinocyte growth arrest in response to differentiative agents such as FBS, TPA and high medium calcium levels, the exact role of this gene product remains unclear.

[Memory-enhancing effects of argipressin and its relationship with periaqueductal gray]

Wistar rats were trained to perform shuttle-box active avoidance response. In experiment A, 43 rats were implanted cannulae in bilateral periaqueductal gray (PAG) and argipressin (Arg) was injected. Arg 0.15 or 0.3 ng but not 0.05 ng retarded the extinction of avoidance response. In experiment B, 37 rats were set up bilateral electrolytic lesions of PAG or sham lesioned. Arg (6 micrograms.kg-1, ip) was injected after training. PAG lesions blocked the influence of ip Arg on memory enhancement. The results indicated that Arg may act directly on CNS to modulated memory and PAG may play an important role in this process. This observation provided further support to the previous suggestion that certain limbic midbrain structures were involved in memory-enhancement by Arg.

Protection of l-arginine against oxygen free radicals-injured rabbit aortic endothelium

This study was to investigate the protective effect of l-arginine, a precursor of endothelium-derived relaxing factor (EDRF), against damages due to endogenous or exogenous oxygen free radicals (OFR) on the aortic endothelium. The superfusion cascade bioassay of rabbit thoracic aorta was used. Endogenous OFR were generated by diethyldithiocarbamate (DETC) to deplete the cytosolic Zn-Cu form of superoxide dismutase (SOD). Exogenous OFR were generated by electrolysis of Krebs' solution. Acetylcholine (ACh) was infused through the donor aortic segment and relaxation of detector aortic ring was used as an indicator of the release of EDRF. The content of malondialdehyde (MDA) in the donor aorta was assayed biochemically. Both DETC and electrolysis inhibited vasodilator responses to ACh and increased MDA content in the aortic segment. Inhibition of DETC was abolished by exogenous SOD. l-Arginine improved impairment of endothelium-dependent relaxation and reduced elevation of MDA content by DETC or electrolysis. These results suggest that l-arginine presents a protective effect of endothelium against damage due to endogenous or exogenous OFR, and that the protective effect of l-arginine may be correlated with reduction in lipid peroxidation.

Increase of an endogenous inhibitor of nitric oxide synthesis in serum of high cholesterol fed rabbits

In the present study, the concentration of NG,NG-dimethylarginine (DMA), an endogenous inhibitor of nitric oxide synthesis, was measured with high-performance liquid chromatography, and the effect of hypercholesterolemia on DMA level was investigated in the high fat, high cholesterol fed rabbit. After 6 weeks on a high fat, high cholesterol diet, serum total cholesterol, triglycerides, and lipid peroxides were increased, and atherosclerosis was shown by means of morphological examination. In these rabbits with atherosclerosis, serum level of DMA was significantly raised, while serum creatine level remained normal. This study suggests that chronic hypercholesteremia may stimulate DMA production through elevation of lipid peroxides. The present results implicate endogenous DMA as a contributor to the development of atherosclerosis.

p21 is a universal inhibitor of cyclin kinases

Deregulation of cell proliferation is a hallmark of neoplastic transformation. Alteration in growth control pathways must translate into changes in the cell-cycle regulatory machinery, but the mechanism by which this occurs is largely unknown. Compared with normal human fibroblasts, cells transformed with a variety of viral oncoproteins show striking changes in the subunit composition of the cyclin-dependent kinases (CDKs). In normal cells, CDKs exist predominantly in multiple quaternary complexes, each containing a CDK, cyclin, proliferating cell nuclear antigen and the p21 protein. However, in many transformed cells, proliferating cell nuclear antigen and p21 are lost from these multiprotein enzymes. Here we have investigated the significance of this phenomenon by molecular cloning of p21 and in vitro reconstitution of the quaternary cell-cycle kinase complexes. We find that p21 inhibits the activity of each member of the cyclin/CDK family. Furthermore, overexpression of p21 inhibits the proliferation of mammalian cells. Our results indicate that p21 may be a universal inhibitor of cyclin kinases.

Expression, regulation, and production of tumor necrosis factor-alpha in mouse testicular interstitial macrophages in vitro

Tumor necrosis factor-alpha (TNF alpha) is a cytokine principally secreted from macrophages and monocytes activated by agents such as lipopolysaccharide (LPS). We have recently shown that TNF alpha inhibited mouse Leydig cell steroidogenesis in vitro. LPS injection has also been shown to repress Leydig cell function and induce TNF alpha messenger RNA (mRNA) expression in testicular interstitial macrophages in vivo. A paracrine regulation of Leydig cell testosterone synthesis by testicular interstitial macrophages via TNF alpha has been proposed. To further support this possibility, we examined whether LPS can induce TNF alpha mRNA expression and protein production in testicular interstitial macrophages in vitro. The regulation of LPS-stimulated TNF alpha mRNA expression in vitro was also investigated by employing the protein synthesis inhibitor cycloheximide (CHX). TNF alpha secretion into culture supernatants was examined by both bioassay and enzyme-linked immunosorbent assay. Isolated testicular interstitial macrophages were cultured for 24 h before the initiation of treatments. Cells were treated with or without LPS (1.0 micrograms/ml) and in the presence or absence of CHX (5.0 micrograms/ml) at different time points. Northern blot analysis showed that TNF alpha mRNA was rapidly and significantly induced by LPS in testicular interstitial macrophages. The peak expression was at 2 h after the treatment, which was 8.3 +/- 2.6-fold over the control (P < 0.05). TNF alpha mRNA then declined quickly and completely disappeared by 8 h after LPS treatment. In contrast to this rapid and transient induction of TNF alpha message by LPS alone, CHX extended the induction and caused a marked increase in LPS-induced TNF alpha mRNA at 2 and 6 h. CHX induced more LPS-stimulated TNF alpha mRNA at 6 h than that at 2 h. At 3 h after LPS treatment, TNF alpha secretion was significantly stimulated (5.6 +/- 1.2 U/micrograms macrophage DNA) measured by L929 tumor fibroblast cytotoxicity. TNF alpha was also detected by enzyme-linked immunosorbent assay in culture media of testicular interstitial macrophages treated with control medium or LPS for 1, 2, and 6 h. TNF alpha secretion was increased in a time-dependent way. There are significantly higher LPS-induced TNF alpha levels in culture media at 2 h (35.4 +/- 2.2 pg/micrograms macrophage DNA) and 6 h (85.5 +/- 11.1 pg/micrograms macrophage DNA) than those in control groups. The current study demonstrates that LPS activates testicular interstitial macrophages to express TNF alpha mRNA and secrete TNF alpha protein in vitro.

Proliferating cell nuclear antigen and p21 are components of multiple cell cycle kinase complexes

We have recently shown that two proteins, proliferating cell nuclear antigen (PCNA) and p21, are associated with cyclin D. Here we show that PCNA and p21 are common components of a wide variety of cyclin/cyclin-dependent kinase complexes in nontransformed cells. These include kinase complexes containing cyclin A, cyclin B, and cyclin D, associated either with CDC2, CDK2, CDK4, or CDK5. We show that PCNA and p21 form separate quaternary complex with each cyclin/CDK and that these quaternary complexes contain a substantial, if not major, fraction of the cell cycle kinases in asynchronously growing cells. These results suggest that PCNA and p21 may perform a common function for all these kinases.

[Delayed gastric liquid emptying in the patients with gastroesophageal reflux disease]

Although there were many reports on gastric emptying in patients with gastroesophageal reflux disease (GERD) in western country, there was no scientific paper about it in Chinese. In 22 cases of GERD, diagnosed by clinical manifestations, endoscopy, histology and 24-hour pH monitoring in the distal portion of esophagus, gastric liquid emptying was measured by using absorption test. The results suggested that the mean time to reach the peak of the serum paracetamol level after taking 500ml water was 34.02 +/- 9.09 min. in 13 healthy adults and 51.14 +/- 23.35 min. in 22 cases of GERD. The difference between the two groups was significant (P < 0.02). Among these 22 patients, 12(54.54%) had delayed gastric emptying, 1 rapid and 9 normal. Our data confirmed that gastric liquid emptying was delayed in some patients with GERD.

Subunit rearrangement of the cyclin-dependent kinases is associated with cellular transformation

In normal human diploid fibroblasts, cyclins of the A, B, and D classes each associate with cyclin-dependent kinases (CDKs), proliferating cell nuclear antigen (PCNA), and p21, thereby forming multiple independent quaternary complexes. Upon transformation of diploid fibroblasts with the DNA tumor virus SV40, or its transforming tumor antigen (T), the cyclin D/p21/CDK/PCNA complexes are disrupted. In transformed cells, CDK4 totally dissociates from cyclin D, PCNA, and p21 and, instead, associates exclusively with a polypeptide of 16 kD (p16). Quaternary complexes containing cyclins A or B1 and p21/CDK/PCNA also undergo subunit rearrangement in transformed cells. Both PCNA and p21 are no longer associated with CDC2-cyclin B1 binary complexes. Cyclin A complexes no longer contain p21, and a new 19-kD polypeptide (p19) is found in association with cyclin A. The pattern of subunit rearrangement of cyclin-CDK complexes in SV40-transformed cells is also shared in those containing adeno- or papilloma viral oncoproteins. Rearrangement also occurs in p53-deficient cells derived from Li-Fraumeni patients that carry no known DNA tumor virus. These findings suggest a mechanism by which oncogenic proteins alter the cell cycle of transformed cells.

The role of tumor necrosis factor-alpha in the regulation of mouse Leydig cell steroidogenesis

Tumor necrosis factor-alpha (TNF alpha), a cytokine secreted by activated macrophages, has been shown to modulate Leydig cell steroidogenesis. The present study examined the regulation of mouse Leydig cell function by TNF alpha at the molecular level. The effects of TNF alpha on both basal and 8-Br-cAMP-stimulated testosterone production, as well as cholesterol side-chain cleavage enzyme (P450scc) and 17 alpha-hydroxylase/C17,20 lyase (P450c17), were investigated. Treatment of Leydig cells with 0.1, 1.0, and 10.0 ng/ml TNF alpha inhibited basal testosterone secretion by 20 +/- 5.0%, 61.1 +/- 6.6%, and 60.7 +/- 5.8% of control, respectively, but had no effects on basal P450scc messenger RNA (mRNA) or protein levels. Treatment of Leydig cells with 8-Br-cAMP caused a 150.7 +/- 32.9-fold increase in testosterone production and marked stimulation of P450scc and P450c17 mRNA and protein accumulation. TNF alpha caused a significant and dose-dependent inhibition of 8-Br-cAMP-stimulated testosterone secretion by 35.9 +/- 9.9%, 90.9 +/- 1.7%, and 96.9 +/- 1.4% with 0.1, 1.0, and 10.0 ng/ml TNF alpha, respectively. TNF alpha also caused a decrease in P450scc and P450c17 mRNA and protein. Treatment with 0.1, 1.0, and 10.0 ng/ml TNF alpha decreased 8-Br-cAMP-stimulated P450scc mRNA by 11.5 +/- 6.9%, 29.3 +/- 2.7%, and 59.2 +/- 8.7%, and decreased 8-Br-cAMP-induced P450c17 mRNA 41.9 +/- 13.5%, 95.7 +/- 2.3%, and 98.5 +/- 1.2%, respectively. The inhibitory effects of TNF alpha on 8-Br-cAMP-stimulated P450 enzyme protein accumulation were also dose dependent, 35.6 +/- 11.4%, 52.9 +/- 14.1%, and 56.0 +/- 7.9% inhibition of P450scc protein levels, and 65.8 +/- 9.4%, 95.5 +/- 1.9%, and 96.9 +/- 2.1% suppression on P450c17 protein levels were observed with 0.1, 1.0, and 10.0 ng/ml TNF alpha, respectively. The inhibitory effect of TNF alpha on 8-Br-cAMP-induced P450c17 mRNA expression was reversible. Within 48 h after the removal of TNF alpha from culture, P450c17 mRNA was restored to 80.6 +/- 3.1% of the level in cultures treated with 8-Br-cAMP alone for 4 days. TNF alpha-mediated inhibition of 8-Br-cAMP-stimulated testosterone secretion from Leydig cells was also reversible. In addition, no significant cell mortality was noted in TNF alpha-treated cells. These data demonstrate that TNF alpha inhibits both basal and 8-Br-cAMP-stimulated testosterone secretion from Leydig cells in a dose-dependent manner.(ABSTRACT TRUNCATED AT 400 WORDS)

Pao, a highly divergent retrotransposable element from Bombyx mori containing long terminal repeats with tandem copies of the putative R region

Analysis of aberrant ribosomal DNA (rDNA) repeats of Bombyx mori resulted in the discovery of a 4.8 kilobase retrotransposable element, Pao. Approximately 40 copies of Pao are present in the genome with most located outside the rDNA units. The complete sequence of one Pao element and partial sequence of four other copies indicated that Pao encodes an 1158 amino acid open-reading frame (ORF). Located within this ORF are domains with sequence similarity to retroviral gag genes, aspartic protease and reverse transcriptase. RNase H and integrase domains were not identified suggesting that the cloned copies were not full-length elements. Pao elements contain long terminal repeats (LTRs) with a central region composed of variable numbers of 46 bp tandem repeats. The variable region appears to correspond to the R region of retroviral LTRs, the region responsible for strand transfer during reverse transcription. Based on a sequence analysis of its reverse transcriptase domain, Pao is most similar to TAS of Ascaris lumbricoides. Pao and TAS represent a subgroup of LTR retrotransposons distinct from the Copia-Ty1 and Gypsy-Ty3 subgroups.

Sequence relationship of retrotransposable elements R1 and R2 within and between divergent insect species

R1 and R2 are retrotransposable elements that integrate at specific sites in the 28S ribosomal RNA (rRNA) genes of Bombyx mori and Drosophila melanogaster. We have previously shown that most insect species contain insertions in their 28S genes at the R1 and/or R2 site. We have sequenced the 3' half of R1 and R2 elements from three additional insect species: the fungus gnat, Sciara coprophila (Diptera); the Japanese beetle, Popillia japonica (Colleoptera); and the parasitic wasp, Nasonia vitripennis (Hymenoptera). The elements were obtained by screening lambda phage genomic clones containing rDNA units and by a polymerase chain reaction approach using degenerate primers to conserved sequences in the reverse-transcriptase domain, in combination with a second primer to the 28S gene 3' of the insertion site. Comparisons of the sequences of R1 and R2 from four insect orders suggest that the organization of their open-reading frames has been conserved and is therefore likely to be similar throughout insects. This sequence analysis also indicates that, except for 5' truncations generated during the retrotransposition process itself, most elements have not accumulated mutations that would make them inactive. Popillia japonica and N. vitripennis differed from previously described species, in that (a) P. japonica contained multiple families of R2 and (b) N. vitripennis contained multiple families of R1. Nucleotide sequence identity between these different families is low. Amino acid sequence identity of their open-reading frames averaged only 41% for the R2 families of P. japonica and 35% for the R1 families of N. vitripennis. The presence of multiple highly divergent families of elements within a species suggests either that each insertion family is able to maintain its copy number without eliminating the other families in its competition for a limited number of 28S genes or that there has been extensive horizontal transfer of R1 and R2 elements between insect species.

D type cyclins associate with multiple protein kinases and the DNA replication and repair factor PCNA

Human cyclin D1 has been associated with a wide variety of proliferative diseases but its biochemical role is unknown. In diploid fibroblasts we find that cyclin D1 is complexed with many other cellular proteins. Among them are protein kinase catalytic subunits CDK2, CDK4 (previously called PSK-J3), and CDK5 (also called PSSALRE). In addition, polypeptides of 21 kd and 36 kd are identified in association with cyclin D1. We show that the 36 kd protein is the proliferating cell nuclear antigen, PCNA. Cyclin D3 also associates with multiple protein kinases, p21 and PCNA. It is proposed that there exists a quaternary complex of D cyclin, CDK, PCNA, and p21 and that many combinatorial variations (cyclin D1, D3, CDK2, 4, and 5) may assemble in vivo. These findings link a human putative G1 cyclin that is associated with oncogenesis with a well-characterized DNA replication and repair factor.

The role of cytokines in the regulation of Leydig cell P450c17 gene expression

Cytokines produced by immune-activated testicular interstitial macrophages (TIMs) may play a fundamental role in the local control mechanisms of testosterone biosynthesis in Leydig cells. We investigated whether in vivo immune-activation of TIMs can modulate Leydig cell steroidogenesis. To immune activate TIMs in vivo, mice were injected intraperitoneally (i.p.) with lipopolysaccharide (LPS, 6 mg/kg). TIMs and Leydig cells were purified for RNA analysis. LPS treatment resulted in a 47-fold increase in interleukin-1β (IL-1β) mRNA in TIMs. P450c17 mRNA levels in the Leydig cells from the same animals, decreased to less than 10% compared to control. The effect of LPS on IL-1β and P450c17 mRNA levels was reversible on both TIMs and Leydig cells, respectively. To determine if the effect of LPS on P450c17 was mediated by a possible decrease in pituitary LH secretion, mice were co-injected with LPS and hCG. Treatment with hCG did not change the effect observed with LPS alone, in TIMs or in Leydig cells. In vitro, LPS treatment of TIMs resulted in marked induction of IL-1β mRNA expression. In parallel, in vitro treatment of Leydig cells with recombinant IL-1 resulted in a dose-dependent inhibition of P450c17 mRNA expression and testosterone production. These data demonstrate that LPS treatment, in vivo and in vitro, induced IL-1 gene expression in TIMs, and that IL-1 inhibits P450c17 mRNA in vitro. Therefore, we suggest that immune-activation of TIMs might have caused the observed inhibition of P450c17 gene expression in Leydig cells in vivo.

Growth-regulated expression of D-type cyclin genes in human diploid fibroblasts

The human CCND1 cyclin D1/PRAD1 gene was previously identified by a genetic screen for G1 cyclin function in Saccharomyces cerevisiae and also was identified as the putative BCL1 oncogene. However, its role in human cell proliferation is not known. To determine if expression of human D-type cyclin genes correlates with the state of cell growth, we examined the level of mRNAs for CCND1 and a related gene, CCND3, in normal human diploid fibroblasts (HDF). The levels of both mRNAs decrease upon serum depletion or at high cell densities. Following stimulation of quiescent fibroblasts with serum, the mRNA levels increase gradually to a peak at about 12 hr, prior to the onset of S phase. Induction of cyclin gene expression by serum is reduced concomitantly with the decline in FOS induction in aging HDFs, suggesting a possible relationship to the decrease in the proliferative response to mitogens during cellular senescence. Cycloheximide partially blocks the induction of CCND1 and CCND3 gene expression by serum, suggesting that both de novo protein synthesis-dependent and -independent pathways contribute to induction. Treatment of HDFs with defined growth factors suggests a correlation between CCND mRNA induction and DNA synthesis. However, induction of these genes is not sufficient for the transition from quiescence through G1 into S phase.

Molecular cloning and chromosomal mapping of CCND genes encoding human D-type cyclins

A human D-type cyclin gene (CCND1/cyclin D1/PRAD1) was previously isolated by virtue of its ability to complement a triple G1 cyclin (Cln) deficiency of Saccharomyces cerevisiae and was also identified as a candidate BCL1 oncogene. We now report the molecular cloning of two additional human D-type cyclin genes, CCND2 (cyclin D2) and CCND3 (cyclin D3). All three human D-type cyclin genes encode small (33-34 kDa) proteins that share an average of 57% identity over the entire coding region and 78% in the cyclin box. The D-type cyclins are most closely related to cyclin A (39% identity) and cyclin E (36%), followed by cyclin B (29%) and cyclin C (21%). Isolation and characterization of genomic clones revealed two pseudogenes corresponding to CCND2 and CCND3, respectively. All three cyclin D genes are interrupted by an intron at the same position. CCND2 has been mapped to chromosome 12p13, and CCND3 has been mapped to chromosome 6p21.

Inhibition of mitochondrial respiratory function by an organic solvent extractable component from an extract of burn eschar

Saline extracts of burn eschar (CEBE) and normal skin (CENS) caused inhibition to mitochondrial respiration and inner membrane function. Ethyl acetate extracts from CEBE (D1) and CENS (D'1) caused depression of the Respiratory Control Ratio, (RCR), an inhibition of respiration rate in state 3 and stimulation to state 4 respiration. Excellent linear correlations exist between the degree of inhibition to state 3, rate of stimulation to state 4 respiration and the logarithm of doses of D1 and D'1. The effective dose ranges (0.75-0.25 mg/ml for D1 and 4-1 mg/ml for D'1) differ by one order of magnitude. The activity of NADH dehydrogenase and succinate dehydrogenase of mitochondria after incubation with the highest toxic dose of D1 or D'1 remained normal. Dinitrophenol (DNP)-stimulated respiration was moderately inhibited by D1 and D'1. No change of oligomycin-sensitive ATPase activity was demonstrated. Exogenous malondialdehyde (MDA) did not show any inhibitory effect. Preliminary studies show that D1 contains a family of free fatty acids (FFA). Incubation of normal mitochondria with D1 increased the content of saturated FFA and a decrease of unsaturated FFA. The role of other peroxidative products is under investigation.