Protective effect of garlic extract against maternal and foetal cerebellar damage induced by lead administration during pregnancy in rats.

BACKGROUND: In spite of its industrial usefulness and varied daily uses, lead (Pb) pollution is a widespread ecological problem that faces the humans in the 21th century. Pb was found to produces a wide range of toxic effects including neurotoxicity especially to the developing and young offspring. Recently, the utilisation of herbal plants has received a significant attention where there has been rising awareness in their therapeutic use; among these is the garlic. In light of the above, the current study is designed experimentally in female pregnant rats in order to investigate the beneficial role of garlic extract in the protection from the maternal and foetal cerebellar damage produced by administration of different doses of Pb during pregnancy. MATERIALS AND METHODS: Positively pregnant female rats were divided into five groups; one control group, two Pb-treated groups (exposed to 160 and 320 mg/kg b.w. of Pb, respectively) and two groups treated with both Pb and garlic (exposed to Pb as previous groups together with 250 mg/kg b.w./day of garlic extract). Treatments started from day 1 to day 20 of pregnancy, where the mother rats of different experimental groups were sacrificed to obtain the foetuses. Pb level in the maternal and foetal blood and cerebellum was estimated by spectrophotometry. Specimens of the cerebellum of different mother and foetal groups were processed to histological and immunohistochemical staining for microscopic examination. RESULTS: The results showed that administration of Pb to pregnant rats resulted in a dose-dependent toxicity for both mothers and foetuses in the form of decrease in maternal weight gain, placental and foetal weights, brain weight and diminished foetal growth parameters, which were prominent in rat's group treated with larger dose of Pb. In Pb-treated rats, Pb level in blood and cerebellum was high when compared with the control group. The histopathological examination of the cerebellum of treated dams and foetuses showed marked alterations mainly in the form of Purkinje cell degeneration and lack of development of foetal cerebellum. Co-treatment of garlic extract along with Pb resulted in a significant decrease in Pb levels as compared with those treated with Pb alone with improvement of the histopathological changes. CONCLUSIONS: This study was useful in evaluating the hazardous effects of uncontrolled use of Pb in general and in assessing the developmental and neurotoxicity of foetuses due to exposure during pregnancy in particular. Co-administration of garlic has beneficial effects in amelioration of Pb-induced neurotoxicity and reversing the histopathological changes of the cerebellum of mother rats and foetuses. (Folia Morphol 2018; 77, 1: 1-15).

p21 and retinoblastoma protein control the absence of DNA replication in terminally differentiated muscle cells.

During differentiation, skeletal muscle cells withdraw from the cell cycle and fuse into multinucleated myotubes. Unlike quiescent cells, however, these cells cannot be induced to reenter S phase by means of growth factor stimulation. The studies reported here document that both the retinoblastoma protein (Rb) and the cyclin-dependent kinase (cdk) inhibitor p21 contribute to this unresponsiveness. We show that the inactivation of Rb and p21 through the binding of the adenovirus E1A protein leads to the induction of DNA replication in differentiated muscle cells. Moreover, inactivation of p21 by E1A results in the restoration of cyclin E-cdk2 activity, a kinase made nonfunctional by the binding of p21 and whose protein levels in differentiated muscle cells is relatively low in amount. We also show that restoration of kinase activity leads to the phosphorylation of Rb but that this in itself is not sufficient for allowing differentiated muscle cells to reenter the cell cycle. All the results obtained are consistent with the fact that Rb is functioning downstream of p21 and that the activities of these two proteins may be linked in sustaining the postmitotic state.

Activated Raf-1 causes growth arrest in human small cell lung cancer cells.

Small cell lung cancer (SCLC) accounts for 25% of all lung cancers, and is almost uniformly fatal. Unlike other lung cancers, ras mutations have not been reported in SCLC, suggesting that activation of ras-associated signal transduction pathways such as the raf-MEK mitogen-activated protein kinases (MAPK) are associated with biological consequences that are unique from other cancers. The biological effects of raf activation in small cell lung cancer cells was determined by transfecting NCI-H209 or NCI-H510 SCLC cells with a gene encoding a fusion protein consisting of an oncogenic form of human Raf-1 and the hormone binding domain of the estrogen receptor (DeltaRaf-1:ER), which can be activated with estradiol. DeltaRaf-1:ER activation resulted in phosphorylation of MAPK. Activation of this pathway caused a dramatic loss of soft agar cloning ability, suppression of growth capacity, associated with cell accumulation in G1 and G2, and S phase depletion. Raf activation in these SCLC cells was accompanied by a marked induction of the cyclin-dependent kinase (cdk) inhibitor p27(kip1), and a decrease in cdk2 protein kinase activities. Each of these events can be inhibited by pretreatment with the MEK inhibitor PD098059. These data demonstrate that MAPK activation by DeltaRaf-1:ER can activate growth inhibitory pathways leading to cell cycle arrest. These data suggest that raf/MEK/ MAPK pathway activation, rather than inhibition, may be a therapeutic target in SCLC and other neuroendocrine tumors.

The adenovirus E1A 289R and 243R proteins inhibit the phosphorylation of p300.

A protein of 300 kDa (p300) associates with the adenovirus E1A proteins and has been implicated in the control of cell cycle progression. In mammalian cells, p300 is actively phosphorylated in both quiescent and proliferating cells and its level of phosphorylation increases as it travels from late G1 into M phase. E1A requires p300 for the induction of cellular DNA synthesis and the repression of enhancer mediated transcription, suggesting that p300 may be involved in pathways that are important to cell proliferation and gene expression. Since the activities of most cell cycle regulatory proteins depend on their phosphorylation state, the possibility exists that certain activities of p300 might also be controlled by phosphorylation and that E1A might in fact be affecting these events. We show here by in vitro analysis that E1A inhibits the phosphorylation of p300 by decreasing the rate of incorporation of phosphate into p300. We also show that p300 can be used as a substrate for the cyclin-dependent p33cdk2 and p34cdc2 kinases, and propose that E1A might be antagonistic to these enzymes in phosphorylating p300. Thus, these results indicate a possible novel function by which E1A can interfere with cellular pathways.

Catheter associated urinary tract infections in neurology and neurosurgical units.

OBJECTIVE: Catheter associated bacteriuria is the most common infection acquired in hospitals. The objective of the study was (1) to study the incidence of bacteriuria following indwelling urethral catheterization in patients with short-term vs long-term catheterization (2) to define the antibiotic resistance pattern among these isolates so that the study can provide guidelines for choosing an effective antibiotic against infections in catheterized patients. METHODS: This is a prospective study carried out over a period of 18 months in Neurology/Neurosurgical patients who had indwelling catheters for > or =48 h. RESULTS: In this study, 68 out of 800 (8.5%) adult inpatients acquired urinary tract infection following indwelling bladder catheterizations. The risk was significantly higher for female, elderly patients, critically ill and patients on prolonged catheterization. Among the bacterial pathogens, Escherichia coli was the commonest organism isolated (32.9%) followed by Pseudomonas sp. (15.1%) and Staphylococcus aureus (12.3%). Candida sp. comprised 13.7% of all isolates. Among Gram negative bacterial pathogens maximum number of isolates were sensitive to Amikacin (sensitivity of 42%). All Gram positive organisms were however sensitive to Vancomycin. CONCLUSIONS: Our results provide guidelines for choosing salvage therapy against hospital resistant strains causing infection in catheterized patients. However, antibiotics seem to prevent urinary tract infections but primarily in patients catherized for short duration, i.e. 3-14 days and not in patients with long-term catheterization.

'Hot flush', an unpleasant symptom accompanying antiandrogen therapy of prostatic cancer and its treatment by cyproterone acetate.

From 1995 to 1997 the authors have assessed 31 patients with histologically verified advanced carcinoma of the prostate (CaP) and the ensuing symptom of 'hot flush'. Patients underwent transurethral resection of the prostate (TURP), bilateral orchiectomy (OE) and combined androgen blockade (CAB) by the administration of non-steroid antiadrogens. The authors present the mechanism of the genesis of the 'hot flush' symptom as well as its subjective manifestations, methods of laboratory monitoring as well as their experience with the treatment of this symptom. 50 mg tablets cyproterone acetate administered twice daily or Androcur depot 300 mg i.m. inj. once in 14 days were the main factors in the treatment of 'hot flushes' which reduced subjective difficulties in 80.6% of the patients studied.

Fournier's gangrene: can aggressive treatment save life?

Fournier's gangrene (FG) is a rapidly progressive, fulminant infection of the scrotum, perineum and the abdominal wall. FG is caused by synergic aerobic and anaerobic organisms. Modern surgical series report mortality of up to 67%. This originally rare disease has become more frequent. Aggressive treatment including antibiotics, antigangrenous serum, and treatment of all accompanied diseases and disorders can be successful. Treatment also includes debridement and plastic corrections. Authors describe management of 8 patients with FG. Treatment of FG and all accompanied diseases was in all cases successful. Treatment costs of this kind of patients were approximately 20 times higher than treatment of patients with other urologic diseases.

[Detection of sarcocystosis in slaughterhouse animals during a veterinary inspection]. / Záchytnost sarkocystózy u jatocných zvierat pri veterinárnej prehliadke.

The objective of our study was to acquire objective data on the finds of sarcocystiosis incidence in particular species of farm animals during veterinary inspection and to compare the efficiency of different direct diagnostic methods: compression and digestion methods. The examined and observed animals involved sheep, cattle, pigs and goats slaughtered in the packing plants at Ruzomberok, Rimavská Sobota, Trstená, Sabinov and Kosice. The animals were subjected to regular veterinary inspection including aspection focused on predilection spots of sarcocyst incidence. Sarcocysts were investigated in detail in 353 head of sheep, 27 goats, 350 head of cattle and 1,409 pigs. The examination consisted in inspection of the whole body, of cross-sections of muscles and organs. The rate of sarcocyst invasion in meat as well as the size of cysts were largely variable. The highest incidence in sheep was observed on the inner surface of ventral muscles in the region of diaphragmatic ribs (21.4%) and in the region of intercostal muscles (39.6%). The rate of sarcocyst invasion in the organs was highest in the gullet with cysts of various forms and size (in 47% of sheep). Veterinary inspection of the total number of 27 goats revealed at aspection the presence of macrocysts in eight goats, which makes 29.62%, and in six head of cattle (1.7%) and in 13 pigs (0.9%). Regular finds of sarcocysts on a slaughter line were confronted with direct diagnostic methods: compression and digestion methods (Fig. 1, Tabs. I, II and III). Direct diagnostic method confirmed different results, while only the digestion method--trypsin digestion of muscle--can be considered as diagnostically reliable.

[Transport of nitrates and nitrites into the milk of dairy cows through the digestive system]. / Prestup dusicnanov a dusitanov do mlieka dojníc cestou tráviaceho traktu.

Increased nitrate concentrations in milk are not only dangerous to human health as the milk is the material for production of baby and infant food, but they cause also many problems in technological milk processing. The study was aimed at the transfer of nitrates and nitrites into milk of dairy cows following nitrate loading. An experiment included 6 dairy cows of the Slovakian Spotted breed at the Experimental Veterinary Centre at Zemplínska Teplica. Prior to start of the experiment samples of feedstuffs and feed water, milk were taken and examined for the presence of nitrates and nitrites. KNO3 in water solution was applied to selected dairy cows in two-week intervals in single peroral doses of 150; 75; 37.5; 18.75 and 9.5 g two hours before evening milking. Nitrate and nitrite residue contents were studied in individual milk samples obtained from manual milking 2, 14, 26, 38 and 50 hours after application of appropriate KNO3 amount. Following the peroral application of KNO3 to dairy cows, a marked increase in nitrate content in milk appeared in dependence on applied KNO3 (Tab. I). Average value of residual nitrate in milk two hours after administration of 150 g of KNO3 was 34.60 mg of NO3-/l. Increased levels of residual nitrate in milk were found also 38 hours after KNO3 application. Nitrate content in milk after 50 hours was almost identical with that that was determined in milk of experimental cows from morning milking on the day of administration of 150 g of KNO3, considered as the control samples. The values of residual nitrate exceeded 0.05 mg neither in single sample of NaNO2/l.(ABSTRACT TRUNCATED AT 250 WORDS)

[Dynamics of methemoglobin levels in the blood of calves in relation to the ingested quantity of nitrates and the transrenal transport of nitrates]. / Dynamika hladín methemoglobínu v krvi teliat v závislosti na mnozstve prijatých dusicnanov a transrenálny prestup dusicnanov.

Changes of methaemoglobin levels were investigated in the blood of suckling calves. Transrenal passage of nitrates was determined in dependence on the ingested amount of nitrates. The experiments were conducted under defined husbandry conditions; no excessive nitrate and nitrite supplementation of the calves by feeds and water could be stated. Imitation of possible field conditions when mainly water, but feeds too, may contain higher nitrate and nitrite levels, was carried out by peroral administration of an aquaeous solution of KNO3 to calves. The administered dose was increased from one to 2, 5 and 10 g per animal and day, respectively, in weekly intervals. MtHb determination in the blood of experimental calves on day 1 and 5 of the administration of 1 g KNO3 revealed no significant values. On day 1 and 5 of the administration of 2, 5 and 10 g KNO3 per animal and day, respectively, a significant increase of MtHb levels in the blood of calves was observed 2 and 3 hours after administration, followed by a decrease 4 hours after administration. The maximum values of MtHb in the blood of experimental calves, observed 3 hours following application of the respective KNO3 dose, were within the tolerance limits of the reference values. In urine, 3 hours after the administration of 10 g of KNO3 a mean nitrate value of 941.40.

[A method of extraction in the detection of residual inhibiting substances in the tissues of pigs and calves after unavoidable slaughter]. / Metodika extraktov v detekcii rezíduí inhibicných látok v tkanivách nevyhnutne zabitých osípaných a teliat.

Differences were studied in detecting residues of inhibitory substances in tissue samples of pigs and calves after emergency slaughter. Samples of liver, heart, kidney and muscle of 30 pigs and 16 calves were examined. Solid samples of organ tissues placed on an agar medium and extracts of the solid samples placed into agar pits were used for detection. Samples were parallelly subjected to the microbiologic diffusion method, using the S. aureus CCM 2022 and B. subtilis CCM 1999 microorganisms. The method of obtaining the extracts from solid samples of the organs was proposed and tested at our own workplace. The presence of inhibitory substances was displayed by the formation of inhibition zones. Results of the positive samples in calves (7 samples) and in pigs (3 samples) point out explicitly to the fact that the extracts of the tissue samples display positively larger inhibition zones in comparison with the solid samples. B. subtilis was demonstrated to be more sensitive than S. aureus, comparing the used microorganisms.

Effect of oral cadmium and zinc application on leukocytes biological activity in Japanese quails (Coturnix coturnix japonica).

Objective of this study was to investigate changes in biological activity of blood leukocytes in Japanese quails, caused by zinc and cadmium administration. Four groups of Japanese quails were used. Three experimental groups of quails were exposed either to Cd (0.12 mg Cd/quail), Zn (4 mg Zn/quail) or a combination of Cd and Zn (0.12 mg Cd, 4 mg Zn/quail), which were added daily to the drinking water. The fourth group was the control group. The metabolic activity of phagocytes and mitogenic activation of lymphocytes to phytohemaglutinine (PHA) were determined on day 37, 58 and 118 of exposure. The numbers of peripheral blood leukocytes of Japanese quail after cadmium and zinc addition in all groups of birds were without significant differences, however, the functional activities of phagocytes and lymphocytes in the Cd-group of quails were significantly decreased. The metabolic activity of phagocytes decreased significantly at all time points analysed (P < 0.05-0.001) in comparison to the control group and the Cd-Zn group. Similarly, the response of lymphocytes to PHA activation in the Cd exposed group of quails decreased significantly on day 58 and 118 of exposure when compared to the control group (P < 0.05) and Zn-group of quails (P < 0.01). Zn in combination with Cd eliminated the immunotoxic effect of Cd on metabolic activity of phagocytes and improved lymphocyte answer to PHA, when compared to the Cd-group on day 58 and 118 of metal administration. The results of the present study indicate that cadmium caused a significant decrease of metabolic activity of phagocytes and mitogenic activation of lymphocytes in peripheral blood of Japanese quails. Simultaneous administration of Zn and Cd eliminated the immunotoxic effect of Cd on functional activity of phagocytes and lymphocytes, and zinc improved both investigated functional parameters of immune cells.

Atividade antioxidante de Piper arboreum, Piper dilatatum e Piper divaricatum / Antioxidant activity of Piper arboreum, Piper dilatatum, and Piper divaricatum

Os óleos essenciais de P. arboreum, P. dilatatum e P. divaricatum foram obtidos por hidrodestilação e analisados por CG-DIC e CG-EM. Extratos etanólicos foram preparados por extração exaustiva. A atividade antioxidante de óleos e extratos foi avaliada por meio do método de sequestro de radicais livres usando 2,2-difenil-1-picril-hidrazila. Os teores de óleos essenciais foram de 0,98%, 1,50% e 0,99% para P. arboreum, P. dilatatum e P. divaricatum, respectivamente. Esses óleos demonstraram riqueza em sesquiterpenos, sendo os principais componentes: biciclogermacreno (28,7%) e ß-copaen-4-α-ol (13,3%) para P. arboreum; germacreno D (16,7%), α-alaskeno (18,9%) e viridiflorol (12,5%) para P. dilatatum; e germacreno D (9,4%), valenceno (11,1%) e γ-cadineno (11,0%) para P. divaricatum. No teste de atividade antioxidante, com base nas percentagens de sequestro de radicais, foram determinados a concentrações efetivas (CE50) e o Índice de Atividade Antioxidante (IAA). Os seguintes valores de CE50 e IAA foram encontrados: ácido ascórbico (usado como referência) 226,84 µg.mL-1 e 5,30; extrato de P. arboreum 239,60 µg.mL-1 e 4,90, e extrato de P. dilatatum 367,70 µg.mL-1 e 3,20, respectivamente. A metodologia utilizada para a atividade antioxidante mostrou-se inadequada para o extrato da P. divaricatum. Os óleos essenciais não apresentaram atividade antioxidante significativa, entretanto, os extratos etanólicos de P. arboreum e de P. dilatatum apresentaram atividade antioxidante expressiva.

were obtained by means of hydrodistillation and analyzed by GC-FID and GC-MS. The ethanolic extracts were prepared by exhaustive extraction. The antioxidant activity of the oils and extracts were evaluated by applying the free radical scavenging method using the 2,2-diphenyl-1-picrylhydrazyl radical. The yields of the essential oils were 0.98%, 1.50% and 0.99% for P. arboreum, P. dilatatum and P. divaricatum, respectively. The oils are rich in sesquiterpenes, and the main components of P. arboreum are the bicyclogermacrene (28.7%) and ß-copaen-4-α-ol (13.3%); of P. dilatatum, the germacrene D (16.7%), α-alaskene (18.9%) and viridiflorol (12.5%); and of P. divaricatum, the germacrene D (9.4%), valencene (11.1%) and γ-cadinene (11.0%). The antioxidant activity test, based on the percentages of radical scavenging, determined the effective concentrations (CE50) and the Antioxidant Activity Index (AAI). The following CE50 and AAI values were found: 226.84 µg.mL-1 and 5.30 for ascorbic acid (used as the reference), 239.60 µg.mL-1 and 4.90 for P. arboreum, and 367.70 µg.mL-1 and 3.20 for P. dilatatum. The antioxidant evaluation using this methodology is not applicable for the P. divaricatum extract. These essential oils did not present a significant antioxidant activity. However, the ethanolic extracts of P. arboreum and P. dilatatum did show a strong antioxidant

Cyclin-dependent kinases phosphorylate the adenovirus E1A protein, enhancing its ability to bind pRb and disrupt pRb-E2F complexes.

The adenovirus E1A protein of 243 amino acids has been shown to affect a variety of cellular functions, most notably the immortalization of primary cells and the promotion of quiescent cells into S phase. The activity of E1A is derived, in part, from its association with various cellular proteins, many of which play important roles in regulating cell cycle progression. E1A is known to have multiple sites of phosphorylation. It has been suggested that cell cycle-dependent phosphorylation may also control some of E1A's functions. We find now that immune complexes of cyclin-dependent kinases such as cdk4, cdk2, and cdc2 are all capable of phosphorylating E1A in vitro. Additionally, the sites on E1A phosphorylated by these kinases in vitro are similar to the E1A sites phosphorylated in vivo. We have also found that a phosphorylated E1A is far more efficient than an unphosphorylated E1A in associating with pRB and in disrupting E2F/DP-pRB complexes as well. On the basis of our findings and the differences in timing and expression levels of the various cyclins regulating cdks, we suggest that E1A functions at different control points in the cell cycle and that phosphorylation controls, to some extent, its biological functions.

Place of transvaginal sonography in the evaluation of reproductive endocrinology.

A high frequency vaginal probe with improved resolution offers a remarkable sharp clear image of pelvic organs. This is possible because of its closed proximity with target organ and non-intervention by gut or omentum. Study of ovarian follicular dynamics (folliculometry), identification of proliferative, secretory and decidual changes of endometrium (endometrial dating) in different phases of menstrual cycle and imaging of mucus secretion in the cervical canal (cervical mucus study) in the pre-ovulatory phase is possible by transvaginal probe. It is non-invasive, acceptable to patients, and thus can be repeated any number of times. A close serial monitoring offers immense wealth of information about the anatomical as well as reproductive endocrinal status of the patient. Ovulation can be predicted in advance. The case of dysovulation can be identified in first cycle of study; corrective therapy can be started in another two or three cycles, aiming at achieving perfect folliculogenesis. Once well tuned synchronised cycle is restored, the pregnancy outcome is remarkable. Thus transvaginal sonography offers one of the best reproductive endocrinology evaluation in the hand of a modern gynaecological sonologist and infertility specialist.

Role of transvaginal sonography in pelvic scan for female reproductive system.

Three hundred twenty-nine cases of early pregnancy and 116 pelvic pathology studied by transabdominal sonography were compared with 81 cases of early pregnancy and 88 cases of pelvic pathology subjected to transvaginal sonography. A high frequency vaginal probe, because of its close proximity with the target organ, produces remarkably sharp image. An accurate diagnosis is possible in great majority of cases within a short time. Vaginal sonography is done with an empty bladder. A close serial monitoring of ovarian follicles, endometrium and cervical mucus with transvaginal sonography offers an immense wealth of information about the structural and reproductive endocrinal status of the patient. Ovulation can be predicted in advance. Imaging of female reproductive system by transvaginal sonography is indispensable for any modern gynaecological care and for infertility assessment in particular.

A role for histone deacetylase HDAC1 in modulating the transcriptional activity of MyoD: inhibition of the myogenic program.

The molecular mechanism(s) that are responsible for suppressing MyoD's transcriptional activities in undifferentiated skeletal muscle cells have not yet been determined. We now show that MyoD associates with a histone deacetylase-1 (HDAC1) in these cells and that this interaction is responsible for silencing MyoD-dependent transcription of endogenous p21 as well as muscle-specific genes. Specifically, we present evidence that HDAC1 can bind directly to MyoD and use an acetylated MyoD as a substrate in vitro, whereas a mutant version of HDAC1 (H141A) can not. Further more, this mutant also fails to repress MyoD-mediated transcription in vivo, and unlike wild-type HDAC1 it can not inhibit myogenic conversion, as judged by confocal microscopy. Finally, we show that an endogenous MyoD can be acetylated upon its conversion to a hypophosphorylated state and only when the cells have been induced to differentiate. These results provide for a model which postulates that MyoD may be co-dependent on HDAC1 and P/CAF for temporally controlling its transcriptional activity before and after the differentiation of muscle cells.

Inactivation of p21 by E1A leads to the induction of apoptosis in DNA-damaged cells.

A major impediment to successful chemotherapy is the propensity for some tumor cells to undergo cell cycle arrest rather than apoptosis. It is well established, however, that the adenovirus E1A protein can sensitize these cells to the induction of apoptosis by anticancer agents. To further understand how E1A enhances chemosensitivity, we have made use of a human colon carcinoma cell line (HCT116) which typically undergoes cell cycle arrest in response to chemotherapeutic drugs. As seen by the analysis of E1A mutants, we show here that E1A can induce apoptosis in these cells by neutralizing the activities of the cyclin-dependent kinase inhibitor p21. E1A's ability to interact with p21 and thereby restore Cdk2 activity in DNA-damaged cells correlates with the reversal of G(1) arrest, which in turn leads to apoptosis. Analysis of E1A mutants failing to bind p300 (also called CBP) or Rb shows that they are almost identical to wild-type E1A in their ability to initially overcome a G(1) arrest in cells after DNA damage, while an E1A mutant failing to bind p21 is not. However, over time, this mutant, which can still target Rb, is far more efficient in accumulating cells with a DNA content greater than 4N but is similar to wild-type E1A and the other E1A mutants in releasing cells from a p53-mediated G(2) block following chemotherapeutic treatment. Thus, we suggest that although E1A requires the binding of p21 to create an optimum environment for apoptosis to occur in DNA-damaged cells, E1A's involvement in other pathways may be contributing to this process as well. A model is proposed to explain the implications of these findings.

Inactivation of p27Kip1 by the viral E1A oncoprotein in TGFbeta-treated cells.

The adenovirus oncoprotein E1A and the simian virus SV40 large T antigen can both reverse the strong growth-inhibitory effect of transforming growth factor(TGF)-beta on mink lung epithelial cells: exposure of TGF-beta causes these cells to arrest late in the G1 phase of the cell cycle (ref. 3). This arrest correlates with an increase in expression of the protein p15Ink4B (ref. 4), inactivation of the cyclin E/A-cdk2 complex by the inhibitory protein p27Kip1 (refs 5-7), and with the accumulation of unphosphorylated retinoblastoma protein. The rescue by E1A of cells from TGF-beta arrest is partly independent of its binding to retinoblastoma protein. Here we show that E1A directly affects the cyclin-dependent kinase inhibitor p27Kip1 in TGF-beta-treated cells by binding to it and blocking its inhibitory effect, thereby restoring the activity of the cyclin-cdk2 kinase complex. In this way, E1A can overcome the effect of TGF-beta and modulate the cell cycle. To our knowledge, E1A provides the first example of a viral oncoprotein that can disable a cellular protein whose function is to inhibit the activity of cyclin-dependent kinases.