Plant cells contain a novel member of the retinoblastoma family of growth regulatory proteins

The product of the retinoblastoma susceptibility gene (Rb) controls the passage of mammalian cells through G1 phase. Animal virus oncoproteins interact with the Rb protein via an LXCXE motif and disrupt Rb-E2F complexes, driving cells into S-phase. Recently, we found that the RepA protein of a plant geminivirus contains an LXCXE motif that is essential for its function, a finding that predicts the existence of Rb-related proteins in plant cells. Here we report the isolation of a maize cDNA clone encoding a protein (ZmRb1) which, based on structural and functional studies, is closely related to the mammalian Rb family of growth regulatory proteins. ZmRb1 shows a high degree of amino acid conservation when compared with animal Rb members, particularly in the A/B 'pocket' domain, but ZmRb1 has a shorter N-terminal domain. ZmRb1 forms stable complexes with plant LXCXE-containing proteins, e.g. geminivirus RepA protein. Geminivirus DNA replication is reduced in plant cells transfected with plasmids encoding either ZmRb1 or human p130, a member of the Rb family. This suggests that ZmRb1 controls the G1/S transit in plant cells and is consistent with the fact that geminiviruses need an S-phase environment for DNA replication, as animal DNA tumor viruses do. Our results allow the extension of the Rb family of tumor suppressor proteins to plants and have implications on animal and plant strategies for cell growth control.

HIV infection and AIDS in China, 1985 through 1994

OBJECTIVES

This paper analyzes data on the distribution of and risk factors for the acquired immunodeficiency syndrome (AIDS) and human immunodeficiency virus (HIV) infection in China.

METHODS

Ten years of data on persons tested for HIV infection and AIDS and the proportion who tested positive were analyzed against the background of China's population count. The Chinese- and English-language literature on HIV and AIDS from 1985 through 1995 was also reviewed.

RESULTS

Overall, more males than females had HIV infection. Intravenous drug use was the primary source of transmission, followed by heterosexual contacts. Only a small number of the persons tested were homosexual, but their proportion of HIV seropositivity ranked third to that of drug users; that of general hospital patients ranked fourth.

CONCLUSIONS

HIV infection and AIDS in China began as a highly regionalized and largely rural problem in Yunnan Province. However, HIV infection and AIDS have become an emerging urban problem. HIV seropositivity is low among several groups thought to have an elevated risk.

Height of the residual ridge and radiographic appearance of bony structure in the jaws of clinically edentulous elderly people

Alveolar atrophy and its relation to osteopenia of the mandible were studied in 124 edentulous 76-, and 81- and 86-year-old subjects (32 males and 92 females). Both variables were assessed visually from panoramic radiographs. Mandibular alveolar atrophy was found to be more severe in women (P < 0.001). No statistically significant differences were found between the three age-groups in mandibular alveolar atrophy, nor between the sexes or age-groups in maxillary alveolar atrophy. The structure of the mandibular bone was osteopenic in 38 patients (30.7%), a situation that was more frequent in women (P < 0.001). The relationship between the observed osteopenia and the severity of the mandibular alveolar atrophy in women was statistically significant (P < 0.05).

IL-12 protects mice against pulmonary and disseminated infection caused by Cryptococcus neoformans

We examined the role of IL-12 in host resistance to Cryptococcus neoformans using a murine model of pulmonary and disseminated infection. In this model, mice were infected intratracheally with viable yeast cells. Mice untreated with IL-12 allowed an uncontrolled multiplication of yeast cells in the lung with infiltrations of few inflammatory cells, and a cryptococcal dissemination to the brain and meningitis by 3 weeks, resulting in death of all animals within 4-6 weeks. IL-12, when administered from the day of tracheal infection for 7 days, induced a marked infiltration of inflammatory cells, consisting mostly of mononuclear cells, and significantly reduced the number of viable yeast cells in the lung. The treatment suppressed brain dissemination, as shown by a marked reduction of yeast cells in the brain and prevention of meningitis. These effects resulted in a significant increase in the survival rate of infected mice. In contrast, late administration of IL-12 commencing on day 7 after instillation of yeast cells failed to protect the mice against infection with C. neoformans. In further experiments, early administration of IL-12 markedly induced interferon-gamma (IFN-gamma) mRNA in the lungs of infected mice, while no IFN-gamma mRNA was detected without this treatment. Our results indicate that IL-12 is effective when administered in the early period of pulmonary cryptococcal infection.

Molecular cloning of a novel allele of SMR1 which determines sulfometuron methyl resistance in Saccharomyces cerevisiae

A different mutation (SMR1B) to SMR1-410 (ilv2), which determines resistance to sulfometuron methyl in Saccharomyces cerevisiae, was cloned by PCR. Sequence analysis indicated a C to T change at position 575 of the ILV2 coding sequence, which results in a proline transition to leucine at position 192. Similarly to SMR1-410, the SMR1B gene was confirmed as a convenient dominant selective marker for yeast transformation including industrial strains.

Effect of head positioning in panoramic radiography on vertical measurements: an in vitro study

OBJECTIVE

To assess whether it is possible to make accurate vertical measurements of the jaws from panoramic radiographs.

METHODS

Five dry skulls were shifted 5 mm forwards and backwards and tilted 5 degrees up and down in the sagittal plane. Panoramic radiographs of each skull were obtained in nine different positions. In the maxilla, three reference lines were used and vertical measurements were made at the distal surfaces of the first premolar and first molar and in the midline. In the mandible, measurements were made at the distal surfaces of the first premolar and first molar, and at the mental foramen on both sides, and in the midline. The points and lines were marked manually and the radiographs were digitized, magnified and measured.

RESULTS

Sagittal shifting and tilting had only a slight effect on measurements in the mandible. Sagittal tilting of the head had the greatest effect on all the measurements made from the line between the articular eminences to the alveolar crest, as well as measurements in the maxillary midline.

CONCLUSIONS

The line between the articular eminences is unsuitable as a reference line for measurements of the tooth-bearing areas. A slight misalignment of the head does not significantly affect the vertical measurements in the mandible or of the posterior maxilla if the reference lines are in the same vertical plane as the teeth.

Marek's disease virus (MDV) ICP4, pp38, and meq genes are involved in the maintenance of transformation of MDCC-MSB1 MDV-transformed lymphoblastoid cells

An antisense strategy has been used to identify genes important for the maintenance of transformation of MDCC-MSB1 (MSB1) Marek's disease virus-transformed lymphoblastoid cells. Oligodeoxynucleotides antisense to the predicted translation initiation regions of ICP4 and pp38 mRNAs inhibited proliferation of MSB1 cells but not MDCC-CU91 (CU91) reticuloendotheliosis virus-transformed cells. Control oligodeoxynucleotides having the same base composition but a different sequence did not inhibit MSB1 cell proliferation. In addition, ICP4 and pp38 antisense oligodeoxynucleotides resulted in 77- and 100-fold reductions in colony formation by MSB1 cells in soft agar, respectively. To extend and corroborate these results, a novel system based on efficiently regulated expression of eukaryotic genes by a chimeric mammalian transactivator, LAP267 (S. B. Baim, M. A. Labow, A. J. Levine, and T. Shenk, Proc. Natl. Acad. Sci. USA 88:5072-5076, 1991), was used. MSB1-derived stably transfected cell lines in which RNA antisense to Marek's disease virus ICP4, pp38, or meq could be induced by treatment of the cells with isopropyl-beta-D-thiogalactopyranoside (IPTG) were constructed. Control cell lines in which expression of ICP4 sense or pUC19 sequences could be induced by IPTG were also constructed. Induction of the cell lines indicated that ICP4 antisense RNA, but not ICP4 sense RNA or pUC19 RNA, inhibited proliferation of MSB1 cells. Induction of ICP4, meq, or pp38 antisense RNAs, but not ICP4 sense or pUC19 RNAs, had a dramatic effect on relative colony formation by MSB1 cells in soft agar. These results indicate that ICP4, pp38, and Meq are all involved in the maintenance of transformation of MSB1 cells.

Contribution of interferon-gamma in protecting mice during pulmonary and disseminated infection with Cryptococcus neoformans

In the present study, the role of interferon-gamma (IFN-gamma) in the host resistance against Cryptococcus neoformans was examined using a murine model of pulmonary and disseminated infection. In this model, mice were infected intratracheally with live yeast cells, and the histological changes in the lungs and the number of microorganisms in the lung and brain were compared in mice treated and untreated with anti-IFN-gamma monoclonal antibody (mAb) to define the contribution of endogenously synthesized IFN-gamma in the natural course of infection. Administration of this mAb reduced the accumulation of inflammatory cells in the alveolar septa, peribronchial and perivascular areas, and promoted the expansive growth of microorganisms in the alveoli and destruction of alveolar structure. The neutralization of endogenous IFN-gamma by mAb increased the number of microorganisms in the lung and brain, and significantly shortened the survival time of infected mice. On the other hand, administration of IFN-gamma decreased the number of microorganisms in these organs, and significantly extended their survival time. Considered together, our results suggest that endogenous IFN-gamma protects mice from infection with C. neoformans by inducing a cellular inflammatory response, potentiating the clearance of microorganism from the lungs and preventing its dissemination into the central nervous system.

[Missed diagnosis in prostate incidental carcinoma]

522 cases of benign prostate hyperplasia from 1980 to 1994 were reviewed. Prostate incidental carcinoma (PIC) was identified in 26 cases (4.98%). In order to study the pathomorphological features and to study the causes for missed diagnosis of this entity, the authors observed and analysed the numbers of carcinomatous foci their distribution, classification, staging and differentiation, morphological features and prostate specific antigen (PSA) markers. It was found that 23 cases exhibited a pathological structure of uniform pattern and 3 cases with pluriform pattern. Adenocarcinoma was most common. 17 cases were A1 stage and 9 cases were A2 stage. Isolated multiple foci of invasion and alterations of architecture are important pathological features of these cases. Missed diagnosis of prostate cancer is related to the small amount of biopsy tissue, contrast between benign and malignant prostate epithelial tissue not distinct, scarce nuclear anaplasia, careless microscopic observation, or observer lacks the ability to differentiate between pathologic types and pluriform patterns. Different PSA reactions may be related to tumor differentiation and classification.

Changes in the position of the mental foramen as a result of alveolar atrophy

The location of the mental foramen has often been claimed to be unaffected by alveolar atrophy. In the present study, the distances of the mental foramen and the mandibular canal from the lower cortex of the mandible were compared in a radiographed series of 40 edentulous elderly women with advanced alveolar atrophy and 40 elderly women who had 10 or more lower teeth left. The mental foramen was situated on average 3.8 mm lower in dentulous jaws than in dentulous jaws (P < 0.0001). The mandibular canal was also situated lower in edentulous jaws, but the difference was not statistically significant. The results confirm the finding that the mental foramen seems to descend as a result of alveolar atrophy.

Identification and analysis of a retinoblastoma binding motif in the replication protein of a plant DNA virus: requirement for efficient viral DNA replication

Geminiviruses are plant DNA viruses with small genomes whose replication, except for the viral replication protein (Rep), depends on host proteins and, in this respect, are analogous to animal DNA tumor viruses, e.g. SV40. The mechanism by which these animal viruses create a cellular environment permissive for viral DNA replication involves the binding of a virally encoded oncoprotein, through its LXCXE motif, to the retinoblastoma protein (Rb). We have identified such a LXCXE motif in the Rep protein of wheat dwarf geminivirus (WDV) and we show its functional importance during viral DNA replication. Using a yeast two-hybrid system we have demonstrated that WDV Rep forms stable complexes with p130Rbr2, a member of the Rb family of proteins, and single amino acid changes within the LXCXE motif abolish the ability of WDV Rep to bind to p130Rbr2. The LXCXE motif is conserved in other members of the same geminivirus subgroup. The presence of an intact Rb binding motif is required for efficient WDV DNA replication in cultured wheat cells, strongly suggesting that one of the functions of WDV Rep may be the linking between viral and cellular DNA replication cycles. Our results point to the existence of a Rb-like protein(s) in plant cells playing regulatory roles during the cell cycle.

Cloning and molecular analysis of two different ILV5 genes from a brewing strain of Saccharomyces cerevisiae

Two different ILV5 genes encoding acetohydroxy-acid isomeroreductases, and named ILV5G and ILV5X, were cloned and sequenced from a Saccharomyces cerevisiae brewing strain. The coding sequence of ILV5X shows a single nucleotide change with respect to that from the ILV5 gene of a S. cerevisiae laboratory strain. In addition, all promoter motifs which are, or are presumed to be, implicated in transcription regulatory functions are identical in ILV5 and ILV5X. In contrast, the coding sequence of ILV5G differs in 5.6% of its nucleotides from that of ILV5 and most of its promoter regulatory motifs show a single nucleotide change with respect to those from ILV5.

The high-output nitric oxide pathway: role and regulation

Nitric oxide synthase (NOS) catalyzes the production of nitric oxide (NO), a short-lived radical gas with physiological or pathophysiological roles in nearly every organ system. The inducible NO synthase (iNOS) is a high-output isoform compared to the two constitutive NOSs. The iNOS from murine macrophages tightly binds calmodulin as a subunit, and its activity is not dependent on exogenous calmodulin or elevated calcium. This iNOS is induced at the transcriptional level by bacterial lipopolysaccharide (LPS) and interferon-gamma. The promoter region of the murine iNOS gene contains at least 24 oligonucleotide motifs corresponding to elements involved in the binding of transcription factors in the promoters of other cytokine-inducible genes. Nuclear factor NF-kappa B/c-rel, interacting with cycloheximide-sensitive protein(s) and binding to the NF-kappa Bd site in the iNOS promoter, controls the induction of iNOS by LPS. However, iNOS is also regulated posttranscriptionally. Complex regulation of iNOS at multiple levels may reflect the dual role of iNOS in host defense and autotoxicity.

Radiographic findings in the jaws of clinically edentulous old people living at home in Helsinki, Finland

In the present survey the radiographic findings in the jaws of 124 clinically edentulous old people living at home in Helsinki, Finland, were studied, using panoramic radiography supplemented by intraoral radiographs. Only 9% of the subjects had root remains. Impacted teeth were found in 4%, radiolucent lesions in 3%, and radiopaque findings in 13%. Deviations from normal condylar structure were found in 17% and mucosal thickenings in the maxillary sinuses in 7%. The mental foramen was situated at the top of the residual ridge in 42% of the subjects. Topically situated mental foramen and condylar changes were commoner in women. The radiographic oral health status of the population studied was good.

Sensibility threshold in patients with masticatory muscle pain

Sensibility and pain thresholds were measured in 27 patients with myofascial pain and craniomandibular disorders and in 19 controls. A monopolar electric stimulator with increasing direct current values was used to record pain and sensibility thresholds in the lower incisors. Patients with myofascial pain had a tendency towards lower sensibility and lower pain thresholds than the controls, although the differences were not statistically significant.

Serum and tissue levels of estradiol during estrogen-induced renal tumorigenesis in the Syrian hamster

The estrogen-induced renal tumor in the hamster has emerged as a major animal model in hormonal carcinogenesis. However, a fundamental aspect of this experimental model has as yet not been investigated. In the present study, comparisons between the serum and tissue 17 beta-estradiol (E2) levels in cyclic female hamsters and corresponding hormone levels in E2-treated castrated male hamsters have been made. Data is provided concerning the concentration of estrogenic hormones in the serum and target tissue typically required to elicit renal tumorigenesis in this species. Serum E2 levels in the cyclic female hamster average 79 pg/ml on days 1-2 and 311 pg/ml on days 3-4, attaining a maximum of 358 pg/ml on day 4 of the cycle. Elevation in uterine, renal and hepatic E2 tissue levels during days 3-4 of the cycle reflect increases in serum E2 levels which were 3.0-, 2.0-, and 2.6-fold higher when compared to day 1 of the cycle in these tissues. As expected, serum E2 levels of untreated castrated male hamsters did not appreciably vary over a 6 month period of aging and averaged about 32 pg/ml. Under conditions which produced essentially 100% renal tumor incidence, a rapid rise in serum E2 levels, averaging 71.0-fold higher than untreated castrated levels, was seen. A steady state serum E2 level of 2400 to 2700 pg/ml was maintained from 45-180 days of continuous estrogen treatment. Compared to kidneys of untreated hamsters, renal E2 levels in E2-treated hamsters rose only on average 5.4-fold between 15-180 days of hormone exposure. Serum levels of E2-treated hamsters were 5.7- to 8.0-fold higher than those observed in cyclic female hamsters on days 3 and 4. However, at these higher E2-treated serum levels there was no apparent effect either on weight loss or mortality of the animals.

[CT morphology of hepatocellular carcinoma lesions]

The preoperative CT appearances of hepatocellular carcinoma (HCC) lesions in 232 cases were analyzed. According to the CT features in shape, outline and boundary of the tumors, the HCC was divided into 3 Types: Type I--roundish expansive growth type (REG TYPE), Type II--irregular expansive growth type (IREG TYPE), and type III--irregular infiltration growth type (IIG TYPE). Comparing different CT types with findings at laparotomy or pathological specimens, it showed that the intrahepatic tumor dissemination rates of type I, II and III were 18.6%, 37.7%, and 47.8%, respectively. The lymph node metastasis rates were 0, 7.7% and 23.1%, respectively. The portal vein tumor thrombus formation rates were 2.3%, 20.8% and 46.4%, respectively. The proportion of encapsulation (67.4%, 27.3% and 5.28%, respectively) apparently decreased from type I to type III in turn. The differences were statistically significant. From type I to III the resection rate of large sized tumor decreased, and the prognosis was from bad to worse. Survival analysis (Cox's mode) showed significant differences from type I to type III. Therefore, CT classification may be used to evaluate the gross biological behavior of HCC lesions and may be of pathological and clinical relevance.

Experimental study on the corneal endothelium of traumatic cataract

The cell morphology of corneal endothelium in 84 mice with experimental traumatic cataract was investigated with stained corneal buttons. In the experimental group, the boundaries between adjacent corneal endothelial cells were significantly distorted, some cell boundaries manifested degenerative changes that led to coalescence of the cells. The mean density and mean area of endothelial cells of the controls showed significant difference from those of the experimental group during the 12 weeks of observation. The density of endothelial cells decreased from 3,312 +/- 337/mm2 of the control group to 2,944 +/- 418/mm2 in the group of partially opaque lenses and 2,713 +/- 472/mm2 in the group of totally opaque lenses. Meanwhile, the area of endothelial cells and the coefficient of variation also significantly changed correspondingly, and the degree of damage in the corneal endothelium correlated with the degree of the lens opacity.

[Clinical value of the Chengdu classification of non-Hodgkin's lymphomas]

Two hundred forty-nine cases of non-Hodgkin's lymphomas (NHL) were reviewed by using the working classification of NHL (Chengdu, 1985). The results showed that the patients of 249 cases of NHL ranging in age from 5 to 76 years, with the mean age of 42 of the types were separated into three major prognostic groupings as follows: 1. low (41 of 249 cases, small lymphocytic 27 cases, lymphoplasmacytoid 2 cases, follicular cleaved 7 cases, follicular cleaved and noncleaved 5 cases); 2. intermediate (58 of 249 cases, diffuse cleaved 28 cases, diffuse cleaved and noncleaved 27 cases, follicular noncleaved 3 cases); and 3. high grade malignancy (150 of 249 cases, diffuse noncleaved 49 cases, lymphoblastic 41 cases, immunoblastic 13 cases, polymorphic 39 cases, clear cell 2 cases, histiocytic 6 cases). Each group was significantly different from the others (P less than 0.05). The prognosis of patients with angioimmunoblastic lymphadenopathy like T-cell lymphoma (9 of 249 cases) was not more significant (P greater than 0.05) than that of patients with other polymorphic lymphoma (30 of 249 cases). The results showed this Chengdu classification of NHL is good for practice and usage in clinical evaluation and routine surgical pathology.

[Transitional mucosa in carcinoma of large bowel. Mucin histochemical and scanning electron microscopical study]

We studied the mucosa close to the carcinoma of large bowel (CLB) in 200 cases, the carcinoma tissue of CLB in 130 and the mucosa of fetus large bowel in 24 by mucin histochemistry, in addition to the mucosa near CLB studied by scanning electron microscope (SEM) in 25. The results suggested that mucin composition of transitional mucosa (TM) was similar to CLB and large bowel mucosa of the fetus. SEM showed significant changes in TM. The HID/AB Stain suggesting abnormal range of TM was within 2 cm in 68.0% (136/200) of cases of CLB, within 3 cm in 88.5% (177/200) and In SEM abnormal range within 2 cm in 88.0% (22/25). The measurement of TM can provide reference for resectable range of CLB.

[Dynamics of endothelial cells of the peripheral area of cornea]

Clinical corneal buttons of 150 cases were stained with try-pan blue and alizalin red S, so as to compare the relative density of endothelial cells and to analyse the forms of the cell nuclei. The result showed that cell densities of fetal corneal endothelium of 25 cases with fetal period from 19 to 34 weeks, had no significant difference (P > 0.05) between the central and peripheral areas of cornea. However, the cell densities of corneal endothelium of 19 cases, aged from newborn to 53 years, showed a significant difference (p < 0.01). The cell nuclei of the fetal corneal endothelium have elliptic forms mainly, which are similar between central and peripheral area of corneal endothelium. However, the forms show an unstable nucleus morphological structure. From newborn to adult cornea, the nucleus forms of corneal endothelial cells tend to be stable and circular, but there are unstable forms of endothelial cell nuclei dispersed in corneal periphery. This emphasize that the endothelial cells in corneal periphery still keep its cell differential function of development in some degree.

Epitopes on foot-and-mouth disease virus particles. I. Topology

Monoclonal antibodies (MAb) against an O1 Suisse isolate of FMDV were used to identify epitopes on the virus particle and to determine their relative function. Six major antigenic sites containing one or more epitopes were identified using competition ELISA. An epitope relationship is proposed consisting of a trypsin-sensitive sequential site, termed B2/D9, from the codings for the MAb which reacted with it, which was associated with virus infectivity and is probably at or near to the cell-binding site of the virion; a trypsin-resistant, conformational site 1C6/4C9 MAb reaction at which also resulted in neutralization of virus infectivity; a second trypsin-resistant, conformational site 3C8, where again MAb reaction neutralised virus infectivity; a third trypsin-resistant, conformational site 6C3/2G5, at which MAb-dependent neutralisation of virus infectivity was inefficient; a site 3G4, the expression of which was impaired but not destroyed by trypsin treatment, and was not related to virus infectivity; an internal site A8, which appears to be a "12S subunit-specific" site. This work clearly demonstrates for the first time that both trypsin-sensitive and trypsin-resistant neutralisable (infectivity-associated) sites exist on the FMDV particle, and only one of these can be related to the sequential site used to formulate current FMDV peptide vaccines.