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Biomedical subjects

J W Griffith

Publications and source records attributed to J W Griffith.

At least 19 recordsLinked to original sources
PubMed2001

Reinitiated expression of EJras transgene in targeted epidermal cells of transgenic rabbits by cottontail rabbit papillomavirus infection.

Transgenic rabbits carrying the EJras oncogene have been established in our laboratory (Am. J. Pathol. 155 (1999) 315). The expression of the ras gene is targeted to the epidermal keratinocytes using the upstream regulatory region (URR) of the cottontail rabbit papillomavirus (CRPV). All of the transgenic rabbits develop keratoacanthomas at multiple sites in the skin at 2-3 days after birth, and the tumors spontaneously regress in 1.5-2 months. With regression of the keratoacanthomas, the rabbits appear normal and EJras expression is undetectable in their skin. To determine if CRPV infection would reinitiate the expression of the EJras transgene and make the rabbits more sensitive to tumorigenesis, the rabbits were infected with CRPV at 2 months of age when the keratoacanthomas had regressed. This study shows that CRPV infection of the transgenic rabbit skin could shorten the latency required for CRPV papilloma initiation, and significantly increase the tumor growth and persistence rate compared with non-transgenic rabbits. Furthermore, EJras expression became detectable in the CRPV induced papillomas in transgenic rabbits, but not in the papillomas of non-transgenic rabbits. These results indicate that CRPV infection is able to reinitiate the expression of the CRPV URR controlled EJras oncogene carried by the transgenic rabbits and that the expression of EJras can enhance the tumorigenesis of CRPV infection.

Animals↗
PubMed2000

Mutation of cyclin/cdk phosphorylation sites in HsCdc6 disrupts a late step in initiation of DNA replication in human cells.

Cyclin-dependent kinases (Cdk) are essential for promoting the initiation of DNA replication, presumably by phosphorylating key regulatory proteins that are involved in triggering the G1/S transition. Human Cdc6 (HsCdc6), a protein required for initiation of DNA replication, is phosphorylated by Cdk in vitro and in vivo. Here we report that HsCdc6 with mutations at potential Cdk phosphorylation sites was poorly phosphorylated in vitro by Cdk, but retained all other biochemical activities of the wild-type protein tested. Microinjection of mutant HsCdc6 proteins into human cells blocked initiation of DNA replication or slowed S phase progression. The inhibitory effect of mutant HsCdc6 was lost at the G1/S transition, indicating that phosphorylation of HsCdc6 by Cdk is critical for a late step in initiation of DNA replication in human cells.

Amino Acid Substitution↗
PubMed2000

Endocarditis and meningitis caused by Streptococcus suis after cardiac surgery in a sheep.

A female Dorset-cross sheep developed labored respirations and was anorexic, weak, ataxic and febrile (42.0 degrees C) 15 days after implantation of a cardiac device. Clinical pathologic evaluation identified a mild leukocytosis (11,800 cells/microl), neutrophilia (8,969 cells/microl), and hypokalemia (2.9 mmol/L). Despite intensive therapy, the animal was euthanized 7 days later. Necropsy of the sheep revealed meningitis and vegetative endocarditis associated with the cardiac device. Blood cultures collected antemortem and tissue cultures collected at necropsy yielded Streptococcus suis. Histopathology confirmed the diagnosis of bacterial valvular endocarditis and meningoencephalitis. A variety of environmental and host factors are proposed as contributing to the infection, and the zoonotic potential of S. suis is discussed.

Animals↗
PubMed1999

Development of keratoacanthomas and squamous cell carcinomas in transgenic rabbits with targeted expression of EJras oncogene in epidermis.

Activated ras genes have been frequently identified in both benign and malignant human tumors, including keratoacanthoma and squamous cell carcinoma. In this study, we developed two lines of transgenic rabbits in which the expression of EJras has been specifically targeted to the rabbit epidermal keratinocytes, using the upstream regulatory region of cottontail rabbit papillomavirus. All of the F1 transgenic progenies developed multiple keratoacanthomas at about 3 days after birth. The rabbits developed an average of 20 tumors, which usually reached the size of approximately 1 cm in diameter and then spontaneously regressed in about 2 months, similar to keratoacanthoma regression in humans. In addition, up to 18% of the rabbits then developed squamous cell carcinoma at about 5 months of age. The expression of EJras was detectable in all of the keratoacanthomas and squamous cell carcinomas. These results strongly support the involvement of the ras oncogene in both the initiation and regression of keratoacanthoma, and in the development of squamous cell carcinomas. These novel transgenic rabbits, with their consistent tumorigenic phenotype at an early age, high similarity to the human lesions, and easy accessibility for examination, manipulation, biopsy, and treatment, should provide a unique model system for studying ras activation-related tumor initiation, regression, and progression, and for evaluating antitumor therapies.

Animals↗
PubMed1999

Potassium-channel opener cardioplegia is superior to St. Thomas' solution in the intact animal.

BACKGROUND: In isolated hearts, the potassium-channel opener pinacidil is an effective cardioplegic agent. This study tested the hypothesis that pinacidil is superior to St. Thomas' solution in the more clinically relevant intact animal. METHODS: Sixteen pigs were placed on full cardiopulmonary bypass. Hearts underwent 2 hours of global ischemia (10 degrees to 15 degrees C). Either St. Thomas' or 100 micromol/L pinacidil was administered every 20 minutes (10 mL/kg). Preischemic and postreperfusion slopes of the preload-recruitable stroke work relationship were determined. Changes in myocardial adenine nucleotide levels and cellular ultrastructure were analyzed. RESULTS: Pinacidil cardioplegia resulted in an insignificant change in the slope of the preload-recruitable stroke work relationship (40.6+/-2.1 mm Hg/mm before ischemia and 36.5+/-3.7 mm Hg/mm after ischemia; p = 0.466). In contrast, St. Thomas' solution resulted in a significant decrease in the slope after reperfusion (34.3+/-5.5 mm Hg/mm and 13.5+/-2.3 mm Hg/mm; p = 0.003). Adenine nucleotide levels, myocardial tissue water, and ultrastructural changes were similar between groups. CONCLUSIONS: Pinacidil ameliorated myocardial stunning associated with traditional hyperkalemic cardioplegia without causing significant differences in cellular metabolism.

Adenine Nucleotides↗
PubMed1999

Detection of Björk-Shiley convexo-concave heart valve outlet strut single leg separations: consensus image acquisition and interpretation using two different cineradiographic imaging technologies.

BACKGROUND: Conventional cineradiology has been used clinically to detect partially broken outlet struts (single leg separations, SLSs) in normally functioning Björk-Shiley convexo-concave (C/C) heart valves. The value of radiographic screening has, however, been debated in the medical literature. This study uses the same radiographic technique in sheep implanted with known-status C/C valves in combination with a newly developed geometric image magnification radiography system. This study was designed to test whether sensitivity and specificity of radiographic screening of C/C valves in detecting SLSs could be improved through the combination of readers and imaging modalities. METHODS: Twenty-one sheep with mitral C/C valves were studied on both systems. Five were used for extensive scanning training. When operators were expert on both systems, 16 blinded study valves (4 intact and 12 with outlet strut SLSs) were scanned twice on both systems, first on a modified conventional and then a prototype geometric image magnification (Feinfocus(TM)) cineradiographic system by two expert physicians working together. RESULTS: Among the 32 scanned valves, the two combined expert physicians were required to evaluate 40 intact legs and 24 with an SLS. For all SLS valves, the conventional and Feinfocus systems separately detected 50 (12/24) and 54% (13/24), respectively. When the two systems were combined, the final consensus score was correct in 67% (16/24) of all SLS valves. CONCLUSIONS: Combined modality, paired expert physicians detected 67% of all SLSs. The Feinfocus system might be best reserved for those patients in whom the Siemens screening study demonstrates in minimally suspicious (grade 2) or suspicious (grade 3) appearance of a C/C valve outlet strut leg.

Animals↗
PubMed1998

Human melanoma metastasis is inhibited following ex vivo treatment with an antisense oligonucleotide to protein kinase C-alpha.

To determine whether alteration of PKC alpha expression would affect the metastatic potential of human melanoma cells, replicate cultures of C8161 cells were treated in vitro with a phosphorothioate antisense oligodeoxynucleotide (ODN) that specifically inhibits PKC alpha expression (ISIS-3521). Control C8161 cultures were treated with a scrambled sequence ODN, cationic liposomes or were left untreated. Northern blots demonstrated 70% inhibition of PKC alpha mRNA in ISIS-3521-treated cells compared to controls. Metastasis was suppressed by 75% when ISIS-3521-treated cells were injected intravenously into athymic mice. These results show that PKC alpha expression is important in the regulation of human melanoma metastasis.

Animals↗
PubMed1998

In vivo accuracy of two radiographic systems in the detection of Björk-Shiley convexo-concave heart valve outlet strut single leg separations.

OBJECTIVE: Modified cineradiographic systems have been used clinically to detect partially broken outlet struts in normally functioning Björk-Shiley convexo-concave heart valves. Almost all such valves were explanted, presuming that full failure would likely follow. Inasmuch as the clinical setting only rarely permits examination of normally rated valves, the accuracy of radiographic detection cannot be clinically defined. This study uses the clinical radiographic technique in sheep implanted with known-status convexo-concave valves, comparing its accuracy and that of a newly developed, geometric image magnification radiography system. METHODS: Twenty-one sheep with mitral convexo-concave valves were studied on both systems. Five were used for extensive training. When operators were expert with both systems, images of four intact valves and 12 valves with outlet strut single leg separations, along with a seventeenth single leg separation valve used for calibration, were integrated into 112 image sets organized into a balanced incomplete block design for evaluation by eight trained, blinded reviewers. RESULTS: Cineradiography sensitivity was 24% versus 31% for direct image magnification. The odds ratio for detection of single leg separation by direct image magnification versus cineradiography was 2.0 (95% confidence interval, 0.76 to 5.9; p = 0.13). Cineradiography specificity was 93% versus 90% for direct image magnification. Sensitivity and specificity varied markedly by reviewer, with sensitivity ranging from 8% to 55% and specificity from 51% to 100% for the combined technologies. CONCLUSIONS: The data support the need for more intensive training for convexo-concave valve imaging and further investigation of unconventional radiographic technologies. Clinical cineradiography of convexo-concave valves may detect as little as 25% of valves having a single leg separation, underestimating the prevalence of single leg separations and thereby implying more rapid progression to full fracture than is actually the case.

Animals↗
PubMed1998

Rabbit genital tissue is susceptible to infection by rabbit oral papillomavirus: an animal model for a genital tissue-targeting papillomavirus.

Rabbit oral papillomavirus (ROPV) is a mucosatropic papillomavirus which naturally infects oral mucosal sites of domestic rabbits. In this study, we tested the hypothesis that rabbit genital mucosa is also susceptible to ROPV infection by using the athymic mouse xenograft system and adult immunocompetent rabbits. Subrenal xenografts of ROPV-infected rabbit vulvar and penile sheath tissues were strongly positive for ROPV infection by histologic, in situ hybridization, and Southern analyses. Direct inoculation of adult rabbit penises with infectious ROPV produced small raised lesions of approximately 1 by 1 by 1 mm that were ROPV positive by both in situ hybridization and Southern analyses and were also viral capsid antigen positive by immunohistological staining. Infection of rabbit genital tissues with ROPV may be a useful animal model for the study of genital tissue-targeting papillomaviruses.

Animals↗
PubMed1998

Fatal trematodiasis in research turtles.

During a 5-year period, 16 freshwater turtles (Trachemys scripta elegans and Chrysemys picta) that were purchased for research purposes died spontaneously. Clinical signs of disease included lethargy, constant swimming, swimming sideways, hemiplegia, and ulcerative lesions on the carapace. At necropsy, subcutaneous edema, hepatic necrosis, pancreatic necrosis, splenic necrosis, and intestinal parasites were identified. Histologically, trematode eggs were seen within the liver, brain, spleen, kidney, myocardium, lung, pancreas, testes, and bladder, and were associated with granulomatous reactions. The size and distribution of the eggs were consistent with Spirorchis sp. infection, although adults could not be found to confirm the species. Spirorchid flukes are 1 to 2 mm long and inhabit the heart and blood vessels where they produce eggs. Spirorchis parvus are capable of invading various tissues, including pancreas and the central nervous system. The pathogenicity of the flukes seems to be related to widespread deposition of the eggs, which may block small blood vessels within the intestines, causing necrosis and bacteremia. Antemortem diagnosis is made by direct examination of fecal smears for eggs. Postmortem diagnosis is accomplished by examination of tissues for adult parasites and microgranulomas associated with the fluke eggs. The parasite requires a snail intermediate host to complete its life cycle. Intramuscular or oral administration of praziquantel is reported to be an effective treatment.

Animals↗
PubMed1997

A simian virus 40 large T-antigen segment containing amino acids 1 to 127 and expressed under the control of the rat elastase-1 promoter produces pancreatic acinar carcinomas in transgenic mice.

The simian virus 40 large T antigen induces tumors in a wide variety of tissues in transgenic mice, the precise tissues depending on the tissue specificity of the upstream region controlling T-antigen expression. Expression of mutant T antigens that contain a subset of the protein's activities restricts the spectrum of tumors induced. Others showed previously that expression of a mutant large T antigen containing the N-terminal 121 amino acids (T1-121) under control of the lymphotropic papovavirus promoter resulted in slow-growing choroid plexus tumors, whereas full-length T antigen under the same promoter induced rapidly growing CPR tumors, T-cell lymphomas, and B-cell lymphomas. In those instances, the alteration in tumor induction or progression correlated with inability of the mutant large T antigen to bind the tumor suppressor p53. In the study reported here, we investigated the capacity of an N-terminal T antigen segment (T1-127) expressed in conjunction with small t antigen under control of the rat elastase-1 (E1) promoter to induce pancreatic tumors. The results show that pancreases of transgenic mice expressing T1-127 and small t antigen display acinar cell dysplasia at birth that progresses to neoplasia. The average age to death in these mice is within the range reported for transgenic mice expressing full-length T antigen under control of the E1 promoter. These results indicate that sequestering p53 by binding is not required for the development of rapidly growing acinar cell carcinomas. In addition, we provide evidence that small t antigen is unlikely to be required. Finally, we show that the p53 protein in acinar cell carcinomas is wild type in conformation.

Animals↗
PubMed1997

Studies on pyrazinoylguanidine. 5. Temporal effects over 24 weeks demonstrating attenuation of diabetic nephropathy in STZ-diabetic rats.

This study was designed to determine whether pyrazinoylguanidine (PZG) can attenuate diabetic nephropathy in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced within 1 week after a single intraperitoneal dose of STZ (45 mg/kg in 0.05 mol/l sodium citrate buffer). Diabetic rats were divided into five groups. Each group received by gavage for 24 weeks one of the following: vehicle (saline 10 ml/kg, b.i.d.), PZG (35 mg/kg, b.i.d.), captopril (15 mg/kg, b.i.d.), or hydrochlorothiazide (HCTZ, 20 mg/kg, b.i.d.). Insulin (NPH 7.5 U/day) was given subcutaneously. PZG treatment for 24 weeks reduced mortality and attenuated diabetic nephropathy, as indicated by reduced urinary excretion of total protein (79% of control), low-molecular-weight protein (12% of control), and albumin (60% of control). PZG also preserved renal structure and function. Compared to HCTZ or vehicle-treated rats, STZ-diabetic rats receiving either captopril or insulin exhibited decreased excretion of total protein, low-molecular-weight protein, and albumin, as well as amelioration of renal pathology. Collectively, these results indicate that PZG, as well as captopril and insulin, improved longevity and several indices of diabetic nephropathy in STZ-diabetic rats.

Analysis of Variance↗
PubMed1997

Experimental pneumonia virus of mice infection of guineapigs spontaneously infected with Bordetella bronchiseptica.

Guineapigs that were intranasally inoculated with pneumonia virus of mice (PVM) seroconverted to PVM by 11 days post-infection. During the course of study (2-60 days post-infection) no gross or histologic lesions were identified within the lungs that could be attributed to PVM infection. Mild rhinitis and tracheitis were found in most animals and acute purulent bronchopneumonia in two animals, which may have resulted from spontaneous subclinical Bordetella bronchiseptica infection. Viral and bacterial respiratory diseases of the guineapig are briefly reviewed.

Animals↗
PubMed1996

Thymus-leukemia antigen interacts with T cells and self-peptides.

The functional role of the class Ib thymus-leukemia (TL) Ag expressed within the thymic cortex and intestinal mucosa of the mouse remains unknown. In an approach to elucidate the potential functionality of TL, we developed transgenic mice that ectopically express the H-2T18d gene product on essentially all nucleated cells through the control of a heterologous H-2Kb gene promoter. Transgenic mice demonstrated an increase in the number of CD4+ lymphocytes within the thymus and lymph nodes; these cells displayed an altered T cell receptor repertoire possibly suggesting a role for the ectopically expressed TL protein. The TL protein additionally displayed the characteristics of a bona fide transplantation Ag, because skin grafts from transgenic animals onto MHC- and minor histocompatibility Ag-matched nontransgenic recipient mice resulted in a rapid and vigorous immunologic rejection of the allograft. In MLR studies, transgenic stimulator cells induced the proliferation of responders to a level intermediate between genetically identical and H-2-disparate responder-stimulator combinations. The TL protein was also capable of stimulating cytotoxic T lymphocytes, thereby resulting in specific lysis of TL+ target cells. Further data demonstrated that the TL protein assembles with peptides that are modified at the amino terminus, and that TL retains these molecules at the cell surface. Together, these data suggest that H-2T18d is capable of interacting with T cells via a bound peptide. These data further support the possibility that TL may subserve a specialized function within the immunologic system.

Animals↗
PubMed1996

Optic neuropathy following simulation of orbital hemorrhage in the nonhuman primate.

The goal of the study was to determine, using a nonhuman primate (NHP) model, the minimum duration of elevated intraocular pressure (IOP) (induced by an inflated catheter) necessary to produce significant visual system deficits. In Old World monkeys (Macaca mulatta), a catheter was placed retrobulbarly in one orbit and inflated with saline for either 180 min (10 monkeys) or 240 min (six monkeys subjects). Baseline color fundus photographs, monochromatic photography, fluorescein angiography, and IOP measurements were performed preoperatively and at either 2, 4, or 6 weeks postoperatively on both eyes of each monkey prior to killing and histological analysis. Optic neuropathy was demonstrated in eight of these NHPs. In the two most severe cases (240 min inflation condition), complete nerve fiber atrophy with central retinal artery occlusion was observed. Sector nerve fiber atrophy, extending from the temporal disc to beyond the macula, was noted in the other six monkeys, five of which were in the 180 min inflation condition. Thus, optic neuropathy, sufficient to produce visual loss, was noted following increased IOP (> or = 50 mm Hg) for 180 min or 240 min. These data emphasize the need for timely intervention to mitigate the potential detrimental effects of retrobulbar hemorrhage when it occurs in humans.

Animals↗