Biomedical subjects

L C Stephens

Publications and source records attributed to L C Stephens.

At least 19 recordsLinked to original sources

PubMed2005

Phentermine and anaesthesia.

We describe the case of a woman who had two penroperative hypertensive crises that may have been due to her use of phentermine, a little-known sympathomimetic anti-obesity medication. The currently available anti-obesity medications are discussed: phentermine, diethylpropion, and sibutramine; all of which are sympathomimetics possessing noradrenaline and serotonin reuptake inhibitor activity. These medications should be discontinued one week preoperatively and have potential interactions with tramadol and antidepressants. The drug orlistat inhibits gastrointestinal lipase and may lead to fat soluble vitamin (A, D, E, and K) deficiency, so consideration should be given to checking coagulation status preoperatively.

Alfentanil↗

PubMed2002

Combined TRAIL and Bax gene therapy prolonged survival in mice with ovarian cancer xenograft.

We evaluated the antitumor activity of the Bax gene and green fluorescent protein/tumor necrosis factor-related apoptosis-inducing ligand (GFP/TRAIL) fusion gene driven by the human telomerase reverse transcriptase promoter both separately and combined in the human ovarian cancer lines SKOV3ip and DOV13 and human lung cancer line H1299. In vitro study showed that both TRAIL- and Bax-expressing vectors elicited significant cell killing in H1299 and SKOV3ip cells, but only the GFP/TRAIL gene elicited significant cell killing in DOV13 cells. Combined TRAIL and Bax therapy also produced more profound cell killing in SKOV3ip and H1299 cells, but not DOV13 cells without escalation of the vector doses. To further evaluate the combined effects of Bax and TRAIL, abdominally spread tumors were established in nude mice via intraperitoneal inoculation of SKOV3ip cells followed by that of adenoviral vectors. Tumor growth, ascites formation, survival duration and toxicity were evaluated after treatment. We found that treatment using the Bax- or TRAIL-expressing vector alone significantly suppressed tumor growth and ascites formation, and prolonged animal survival when compared with that of using PBS or a control vector. Combined TRAIL and Bax therapy further prolonged survival significantly when compared with therapy using the TRAIL or Bax gene alone. Transgene expression and apoptosis induction were not detected in normal human ovarian epithelial cells in vitro or normal mouse tissues in vivo after intraperitoneal vector administration. Also, liver toxicity was not detected after either treatment. Thus, combined TRAIL and Bax gene therapy may be useful for treatment of abdominally spread tumors.

Animals↗

PubMed2001

Extent and kinetics of recovery of occult spinal cord injury.

PURPOSE: To obtain clinically useful quantitative data on the extent and kinetics of recovery of occult radiation injury in primate spinal cord, after a commonly administered elective radiation dose of 44 Gy, given in about 2 Gy per fraction. METHODS AND MATERIALS: A group of 56 rhesus monkeys was assigned to receive two radiation courses to the cervical and upper thoracic spinal cord, given in 2.2 Gy per fraction. The dose of the initial course was 44 Gy in all monkeys. Reirradiation dose was 57.2 Gy, given after 1-year (n = 16) or 2-year (n = 20) intervals, or 66 Gy, given after 2-year (n = 4) or 3-year (n = 14) intervals. Two animals developed intramedullary tumors before reirradiation and, therefore, did not receive a second course. The study endpoint was myeloparesis, manifesting predominantly as lower extremity weakness and decrease in balance, occurring within 2.5 years after reirradiation, complemented by histologic examination of the spinal cord. The data obtained were analyzed along with data from a previous study addressing single-course tolerance, and data from a preliminary study of reirradiation tolerance. RESULTS: Only 4 of 45 monkeys completing the required observation period (2-2.5 years after reirradiation, 3-5.5 years total) developed myeloparesis. The data revealed a substantial recovery of occult injury induced by 44 Gy within the first year, and suggested additional recovery between 1 and 3 years. Fitting the data with a model, assuming that all (single course and reirradiation) dose-response curves were parallel, yielded recovery estimates of 33.6 Gy (76%), 37.6 Gy (85%), and 44.6 Gy (101%) of the initial dose, after 1, 2, and 3 years, respectively, at the 5% incidence (D(5)) level. The most conservative estimate, using a model in which it was assumed that there was no recovery between 1 and 3 years following initial irradiation and that the combined reirradiation curve was not necessarily parallel to the single-course curve, still showed an overall recovery equivalent to 26.8 Gy (61%). The spinal cords of symptomatic monkeys consistently revealed a mixture of white matter necrosis and vascular injury, but the majority of spinal cords of asymptomatic animals did not exhibit overt lesions detectable by light microscopy. CONCLUSION: Combined analysis with the data of the previous studies yielded firm evidence that the spinal cord has a large capacity to recover from occult radiation injury induced by a commonly prescribed elective dose. This finding strengthens the rationale for selective use of radiotherapy to treat second primary tumors arising in previously irradiated tissues or late recurrences. However, some caution should be exercised in applying quantitative experimental data, because the length of follow-up in these experiments was limited to 2-2.5 years after reirradiation, whereas human myelopathy cases occasionally occur after longer latency. Because there is a large variation in long-term recovery among tissues, the tolerance of other tissues at risk should also be taken into account in prescribing therapy.

Animals↗

PubMed2001

Antitumor activity and bystander effects of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) gene.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been reported to specifically kill malignant cells but to be relatively nontoxic to normal cells. To evaluate the antitumor activity and therapeutic value of the TRAIL gene, we constructed adenoviral vectors expressing the human TRAIL gene and transferred them into malignant cells in vitro and tumors in vivo. The in vitro transfer elicited apoptosis, as demonstrated by the quantification of viable or apoptotic cells and by the analysis of activation of pro-caspase-8 and cleavage of poly(ADP-ribose) polymerase. The intratumoral delivery elicited tumor cell apoptosis and suppressed tumor growth. In comparison with Bax gene treatment, which is toxic to normal cells, TRAIL gene treatment caused no detectable toxicity in cultured normal fibroblasts nor in mouse hepatocytes after systemic gene delivery. Furthermore, coculture of cancer cells expressing TRAIL with those expressing green fluorescent protein (GFP) resulted in apoptosis of both cells, whereas coculture of Bax-expressing cells with GFP-expressing cells resulted in the cell death of the Bax-expressing cells only, which suggested that the transfer of the TRAIL gene resulted in bystander effects. Moreover, culture of cells with medium from TRAIL-expressing cells showed the proapoptotic activity and bystander effect of the TRAIL gene to be not transferable with medium. To further demonstrate the bystander effect of the TRAIL gene, we constructed plasmid vectors encoding GFP-TRAIL or GFP-Bik chimeric proteins. Transfection of the GFP-TRAIL gene into cancer cells resulted in the death of GFP-positive cells and their neighbors, whereas transfection of the GFP-Bik gene killed GFP-positive cells only. Finally, GFP-TRAIL genes, transfected into normal human fibroblasts or bronchial epithelial cells, did not kill such cells, whereas transfected GFP-Bik genes did. Thus, the direct transfer of the TRAIL gene led to selective killing of malignant cells with bystander effect, which suggests that the TRAIL gene could be valuable for treatment for cancers. Together, these results suggest that delivering the TRAIL gene to cancerous cells may be an alternative approach to cancer treatment.

Adenoviridae↗

PubMed2001

Preemptive control of graft-versus-host disease in a murine allogeneic transplant model using retrovirally transduced murine suicidal lymphocytes.

Suicidal lymphocytes could greatly expand the role of allogeneic transplantation by reducing graft-versus-host disease (GVHD) as a barrier to transplantation, but optimization of their use is hindered by the lack of adequate animal models. To develop an animal model that used retrovirally transduced suicidal lymphocytes in a GVHD setting, a well-characterized MHC-matched murine transplant model (B10.BR-->AKR/J) was adapted. B10.BR splenic lymphocytes stimulated with concanavalin A and interleukin 2 were infected with a retrovirus containing the low-affinity nerve growth factor receptor (LNGFR) and the HSV-TK gene and immunomagnetically selected; these LNGFR+/TK+ allogeneic lymphocytes were then cotransplanted with 1 x 10(7) bone marrow cells into lethally irradiated AKR/J recipients. The LNGFR+/TK+ donor lymphocytes persisted in the peripheral circulation for 6 months in both syngeneic and allogeneic settings. Doses of 2 x 10(6) TK+ allogeneic lymphocytes produced GVHD with a severity and time course similar to that induced by naive lymphocytes. Survival of TK+ allogeneic lymphocyte-bearing mice was significantly improved (P = 0.01) when ganciclovir (GCV; 2 mg/day) was administered on days 7-13 post transplant by i.p. injection, demonstrating that GVHD could be prevented. Fluorescence-activated cell sorting analysis demonstrated 4-fold reduction but persistent circulation of LNGFR+ lymphocytes in mice treated with GCV at various time points 1-3 months after transplantation, demonstrating selective killing of GVHD-reactive cells. We conclude that retrovirally transduced LNGFR+/TK+ murine lymphocytes can be produced, persist after transplant, remain alloreactive, and can be killed by GCV administration, resulting in reduced GVHD.

Animals↗

PubMed2001

Successful treatment of primary and disseminated human lung cancers by systemic delivery of tumor suppressor genes using an improved liposome vector.

Delivery of therapeutic genes to disseminated tumor sites has been a major challenge in the field of cancer gene therapy due to lack of an efficient vector delivery system. Among the various vectors currently available, liposomes have shown promise for the systemic delivery of genes to distant sites with minimal toxicity. In this report, we describe an improved extruded DOTAP:cholesterol (DOTAP:Chol) cationic liposome that efficiently delivers therapeutic tumor suppressor genes p53 and FHIT, which are frequently altered in lung cancer, to localized human primary lung cancers and to experimental disseminated metastases. Transgene expression was observed in 25% of tumor cells per tumor in primary tumors and 10% in disseminated tumors. When treated with DOTAP:Chol-p53 and -FHIT complex, significant suppression was observed in both primary (P < 0.02) and metastatic lung tumor growth (P < 0.007). Furthermore, repeated multiple treatments revealed a 2.5-fold increase in gene expression and increased therapeutic efficacy compared to single treatment. Finally, animal survival experiments revealed prolonged survival (median survival time: 76 days, P < 0.001 for H1299; and 96 days, P = 0.04 for A549) when treated with liposome-p53 DNA complex. Our findings may be of importance in the development of treatments for primary and disseminated human lung cancers.

Acid Anhydride Hydrolases↗

PubMed2001

Antitumor efficacy of 26-fluoroepothilone B against human prostate cancer xenografts.

BACKGROUND: Epothilone compounds (e.g. epothilones A and B) represent a new structural class of microtubule inhibitors with the remarkable ability to inhibit tumor growth of multidrug-resistant cell lines at low nanomolar or even subnanomolar concentrations. Unfortunately, this therapeutic efficacy has only been achieved to date with a narrow therapeutic window. Hence, other structural analogs of compounds such as epothilone B are currently being synthesized in the hope that they will demonstrate equivalent antitumor efficacy with reduced systemic toxicity. PURPOSE: To evaluate the relative efficacy and toxicity of selectively modified epothilone compounds. METHODS: Compounds were initially screened for relative cytotoxicity against the human prostate cancer cell lines PC3, LNCaP, MDA PCa 2a and MDA PCa 2b. Growth inhibitory IC50 values of 0.5 to 4 nM were obtained. From this initial screen, one epothilone compound, 26-fluoroepothilone B, was chosen for further evaluation against the growth of s.c.-implanted MDA PCa 2b- and PC3-derived prostate tumors in athymic nude mice. The compound was administered intravenously at 2, 5 and 10 mg/kg after the tumors had reached 300 mm3. Two control groups were used: paclitaxel (40 mg/kg) and saline. RESULTS: Following treatment with 10 mg 26-fluoroepothilone B/kg, there was a sustained decrease in tumor size for 30 days reaching a maximal reduction of 80% when compared with tumor growth in the saline control group. Sustained suppression (> 20 days) of tumor growth was observed following the second drug injection. Although a maximal body weight loss of 30% occurred after the second injection, all mice completely regained their initial body weight in 20 days. A lower dose (2 mg/kg) produced a 58% maximal reduction in tumor size and a 20% body weight loss. Minimal inhibition of tumor growth, however, was obtained with paclitaxel at a maximally tolerated dose (40 mg/kg). Other epothilones tested were either less effective and/or more toxic than 26-fluoroepothilone B. This new fluorinated epothilone compound supports the growth of paclitaxel-dependent Tax-18 mutant CHO cells and produces microtubule bundles similar to those produced by paclitaxel, indicating that the two drugs share a similar mechanism of action. CONCLUSION: A new fluorinated epothilone compound, 26-fluoroepothilone B, has been described that stabilizes microtubule structures based on its support of growth of a mutant paclitaxel-dependent CHO cell line. Its antitumor activity against human prostate cancer in nude mice is superior to that of paclitaxel at equivalent toxic doses. Further research is required to determine optimal dosing strategies and to fully assess the compound's activity against other malignant diseases.

Animals↗

PubMed2001

Radiation-induced morphologic changes in the rhesus monkey (Macaca mulatta) brain.

The right cerebral hemisphere of 24 rhesus monkeys scheduled for necropsy at the completion of another project were studied histopathologically 1-30 days after a single dose of 60Co-irradiation. Histopathologically, inflammation and gliosis consistently occurred at specific time points but varied in severity between individuals. Multifocal hemorrhage, edema, and an acute neutrophilic inflammatory response were observed initially whereas perivascular accumulations of lymphocytes were observed in specimens at the end of the study. Microglia/macrophages were most prominent during the first week after irradiation, whereas astrocytes were reactive throughout the observation period. The early clinical manifestations of the central nervous system (CNS), because of brain irradiation in humans, correspond temporally with acute vascular responses, acute and subacute inflammatory cell responses, and subacute demyelination and reactive astrocytic and microglial responses observed in the rhesus monkey. Initial responses of the CNS to gamma-irradiation may have potential implications for the development of radiation-induced late injury of the CNS.

Animals↗

PubMed2001

Correlation of kidney weight and volume and selected skeletal parameters to sex in the adult rhesus monkey (Macaca mulatta).

This report outlines a comparison of renal weight and volume and selected skeletal parameters to sex in 22 adult male and 156 adult female rhesus macaques. Means and standard deviations for kidney weight and volume, body weight, and radiographic measurements for both males and females are reported. Ninety-five percent confidence intervals and P-values for the mean differences between the sexes for these parameters were also compiled. Male monkeys were larger, but had kidneys of similar size to those of the females. Joint distributions of the radiographic measurements of the first lumbar vertebra and the skull showed that males were larger in both measurements. The distributions of these parameters were clearly separate in males and females, while joint distributions of kidney weight and volume for males and females overlapped almost completely. We found that, regardless of age, sex, weight, or skeletal size, all normal adult rhesus monkeys generally have similar-sized kidneys.

Animals↗

PubMed2001

In vitro and in vivo antitumor effect of the anti-CD26 monoclonal antibody 1F7 on human CD30+ anaplastic large cell T-cell lymphoma Karpas 299.

CD26 is a M(r) 110,000 surface glycoprotein with diverse functional properties, including having a potentially significant role in tumor development, and antibodies to CD26 mediate pleomorphic cellular functions. In this report, we show that binding of soluble anti-CD26 monoclonal Ab 1F7 inhibits the growth of the human CD30+ anaplastic large cell T-cell lymphoma cell line Karpas 299 in both in vitro and in vivo experiments. In vitro experiments show that 1F7 induces cell cycle arrest at the G1-S checkpoint, associated with enhanced p21 expression that is dependent on de novo protein synthesis. Furthermore, experiments with a severe combined immunodeficient mouse tumor model demonstrate that 1F7 treatment significantly enhances survival of tumor-bearing mice by inhibiting tumor formation. Our data therefore suggest that anti-CD26 treatment may have potential clinical use for CD26+ hematological malignancies.

Animals↗

PubMed2000

Antitumor effect of adenovirus-mediated Bax gene transfer on p53-sensitive and p53-resistant cancer lines.

Antitumor effects of the proapoptotic Bax gene have been evaluated in vitro and in vivo by a binary adenovirus system expressing the human Bax gene. Overexpression of the Bax gene in cultured cell lines from human lung carcinoma results in caspase activation, apoptosis induction, and cell growth suppression. Intratumoral injection of adenovirus vector expressing the Bar gene suppressed growth of human lung cancer xenografts established in nude mice. Histological examination of tumors from mice treated with the Bax gene demonstrated high levels of Bax expression and extensive apoptosis in tumors. In comparison with the treatment by an adenoviral vector expressing human p53, the Bax gene can effectively suppress tumor growth in both p53-sensitive and p53-resistant human lung carcinoma cell lines. Toxicity was not detected in liver and other systems in animals treated intralesionally with the Bax gene. Therefore, our results suggest that the Bar gene may be useful in cancer treatment.

Adenoviridae↗

PubMed2000

Elevated expression of hepatic proliferative markers during early hepatocarcinogenesis in hepatitis-B virus transgenic mice lacking mdr1a-encoded P-glycoprotein.

Recent studies have shown that expression levels of the multidrug resistance gene MDR1, which encodes the drug transporter P-glycoprotein, correlate with prognostic outcomes of certain tumor types. These findings suggest that expression of MDR1 may affect tumor behaviors. To address this issue further, we investigated the expression of mdr1a, a human MDR1 homolog, on the development of hepatocellular carcinoma in a transgenic mouse model carrying the liver-targeted expression of human hepatitis-B virus (HBV) surface antigen. The pathogenetic program was compared in HBV mice carrying either mdr1a(+/+) or mdr1a(-/-). We found that the expressions of proliferative activity markers, Ki67 nuclear antigen, and proliferating cell nuclear antigen were elevated in mdr1a(-/-) mice younger than 10 wk in comparison with those in the same age group of wild-type animals. Replication in the hepatic population as determined by bromodeoxyuridine incorporation tended to support observation that mdr1a(-/-) mice exhibited elevated labeling indices in this age group. Moreover, histologic staining and flow-cytometric analysis showed that the mdr1a(-/-) animals exhibited a higher cell population with polyploidy than did the mdr1a(+/+) counterparts of the same age. However, no significant differences in the expression of the liver-injury markers serum alanine transaminase and aspartate transaminase were observed. Although our results showed that absence of mdr1a expression is correlated with modest enhanced proliferative characteristics in the livers at stage before the development of hepatocellular carcinoma, the overall life spans between these two strains of mice were not significantly different. The implication of these findings to the role of P-glycoprotein in tumor development and cancer chemotherapy is discussed.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed2000

Induction of primary cutaneous melanomas in C3H mice by combined treatment with ultraviolet radiation, ethanol and aloe emodin.

The role of ultraviolet (UV) radiation in the induction of nonmelanoma skin cancer is widely accepted, although its precise contribution to the development of primary cutaneous melanoma skin cancer requires further definition. We found that painting aloe emodin, a trihydroxyanthraquinone from Aloe barbadensis, in ethyl alcohol vehicle on the skin of mice in conjunction with exposure to UVB (280-320 nm) radiation results in the development of melanin-containing skin tumors. C3H/HeN mice were treated thrice weekly with aloe emodin in a 25% ethanol in water vehicle and exposed to 15 kJ/m2 UV radiation. Neither ethanol vehicle nor aloe emodin alone induced skin tumors in the absence of UV radiation. In two separate experiments, 20-30% of the mice treated with a combination of UV radiation and ethanol vehicle and 50-67% of the UV-irradiated animals given aloe emodin in ethanol vehicle developed primary cutaneous melanin-containing tumors. The diagnosis of melanoma was established using Fontana silver stain for melanin; these tumors were negative for vimentin and keratin. Melanin-containing melanosomes were observed by transmission electron microscopy in tumors diagnosed as melanomas. Although the mechanism of carcinogenesis in these mice is currently unknown, our findings have led to the development of the first facile murine model for the induction of primary melanoma. This model has the potential to clarify the role of UV radiation in the etiology of malignant melanoma.

Animals↗

PubMed1999

Apoptosis and the Bcl-2 gene family -- patterns of expression and prognostic value in stage I and II follicular center lymphoma.

PURPOSE: The prognostic significance of spontaneous levels of apoptosis and Bcl-2, Bax, and Bcl-x protein expression in follicular center lymphoma (FCL) is unknown. The objectives of this retrospective study were (1) to investigate the relationship between pretreatment apoptosis levels and long-term treatment outcome in patients with Stage I and II FCL; (2) to define the incidence and patterns of Bax and Bcl-x protein expression in human FC; and (3) to determine the relationship of Bcl-2, Bax, and Bcl-x expression with spontaneous apoptosis levels and clinical outcome in localized FCL. METHODS AND MATERIALS: Between 1974 and 1988, 144 patients with Stage I or II FCL were treated. Hematoxylin and eosin (H & E) stained tissue sections of pretreatment specimens were retrieved for 96 patients. Treatment consisted of regional radiation therapy (XRT) for 25 patients, combined modality therapy (CMT) consisting of combination chemotherapy and XRT for 57 patients, and other treatments for 14 patients. Median follow-up for living patients was nearly 12 years. The apoptotic index (AI) was calculated by dividing the number of apoptotic cells by the total number of cells counted and multiplying by 100. Expression of Bcl-2, Bax, and Bcl-x proteins was assessed using immunohistochemistry. RESULTS: The mean and median AI values for the entire group were 0.53 and 0.4, respectively (range: 0-5.2). The AI strongly correlated with cytologic grade, with mean AI values of 0.25 for grade 1, 0.56 for grade 2, and 0.84 for grade 3 (p < 0.0005; Kendall correlation). A positive correlation was present between grouped AI and grouped mitotic index (MI) (p = 0.014). For patients treated with CMT, an AI < 0.4 correlated with improved freedom from relapse (FFR) p = 0.0145) and overall survival (OS) (p = 0.0081). An AI < 0.4 did not correlate with clinical outcome for the entire cohort or for patients receiving XRT only. Staining of tumor follicles for the Bcl-2 protein was positive, variable, and negative in 73%, 15%, and 12% of cases, respectively. Positive staining of tumor follicles was observed in 96% of cases for both the Bax and Bcl-x proteins. Expression of Bcl-2, Bax, or Bcl-x did not correlate with AI or clinical outcome. CONCLUSION: The level of spontaneous apoptosis in pretreatment specimens correlates with cytologic grade of FCL and is a significant predictor of FFR and OS for patients with localized FCL receiving CMT.

Analysis of Variance↗

PubMed1999

Transrectal ultrasound-guided intraprostatic injection of absolute ethanol with and without carmustine: a feasibility study in the canine model.

OBJECTIVES: To develop a reliable intraprostatic injection technique and to define the local and systemic toxicity of intraprostatic injection of dehydrated ethanol with and without carmustine. METHODS: Twenty-three random-source male canines were divided into a control group (n = 3), a dehydrated ethanol-alone group (group 1, n = 10), and a dehydrated ethanol-plus-carmustine group (group 2, n = 10). A reliable intraprostatic injection technique was developed with the control animals. The optimal volume of dehydrated ethanol for intraprostatic injection and the local tissue effects of dehydrated ethanol injection were defined with group 1. The local tissue effects of escalating doses of carmustine were defined with group 2. All animals were injected under general anesthesia using transrectal ultrasound (TRUS) guidance. Fourteen days after injection, a repeated TRUS of the prostate was done, the animals were killed, and the bladder, prostate, and periprostatic tissues were excised for pathologic examination. RESULTS: Sonographic changes in the prostate 2 weeks after injection were present in all group 1 and 2 animals. All prostates had varying amounts of hemorrhagic and coagulative necrosis, which correlated with the TRUS findings. There were no differentiating pathologic features between group 1 and group 2 specimens. The relative amount of necrosis varied with the doses of dehydrated ethanol and carmustine injected, but was not predictable on the basis of the doses administered. Subclinical prostatic microabscesses were identified in 6 of 10 group 1 animals and 4 of 10 group 2 animals. Only group 2 animals had alterations in their blood chemistry results, all of which were self-limited. Two had white blood cell nadirs of less than 2000 5 days after injection. No animals developed incontinence, and there were no rectal injuries. CONCLUSIONS: Intraprostatic dehydrated ethanol and carmustine injections were readily controllable under TRUS guidance and resulted in hemorrhagic and coagulative necrosis of prostatic tissue with minimal associated morbidity and no incontinence in the dog model. Hematologic changes observed in the animals that received carmustine were self-limiting.

Animals↗

PubMed1999

Interactions of apoptosis, proliferation and host age in the regression of the mouse mammary preneoplasia, TM3, carrying an unusual mutation in p53.

We have developed an in vivo model system of mouse mammary preneoplasias in order to examine the cell and molecular changes that occur during tumorigenesis. Most of these preneoplasias are characterized by an alveolar hyperplasia morphologically similar to that present in normal pregnant mammary gland, but have tumor forming capabilities ranging from very low to high. One of these hyperplasias, the TM3 HOG (transformed mammary hyperplastic outgrowth), forms tumors infrequently and has the unusual characteristic of spontaneous regression. We have observed that 7-8 months post-transplantation into the cleared mammary fat pad of a BALB/c mouse, the TM3 hyperplasia will begin to regress, leaving only a sparse ductal tree with remnant alveolar structures by 10-12 months post-transplantation. We have sought to elucidate the mechanism of this regression by determining the apoptotic and proliferative rates of the alveolar cells during TM3 HOG development. Studies show that apoptotic rates in the TM3 HOG are consistently high (4-7%) at all times after transplantation. This apoptotic rate is higher than the rates found in other preneoplasias in our system and approach the rates observed in the normal involuting gland. An unusual p53 mutation, a serine insertion at codon 233, may be causally related to the high spontaneous apoptotic frequencies as well as elevated inducible apoptotic frequencies in TM3. In addition, a sudden decrease ( approximately 63%) in proliferation occurs around 8 months post-transplantation. Furthermore, transplantation experiments indicate that the ability of the 8-month-old host and/or mammary gland to support growth of preneoplastic mammary tissues is markedly diminished compared with 3- or 6-month-old hosts. The results presented here suggest that the persistent high apoptotic rates, concomitant with decreased proliferation rates, may be responsible for TM3's regression and implicate a unique mutant p53 as a causal factor. Additionally, the results suggest that host determinants can interact with specific molecular changes in the preneoplastic cells to influence growth and progression of the preneoplastic populations.

Age Factors↗

PubMed1999

Skin graft survival after external beam irradiation.

Difficulties with skin graft ulceration after radiation therapy for cancer have led many to question the suitability of this method of soft-tissue coverage and its cost-effectiveness. The objective of this study was, therefore, to assess skin-graft integrity subjected to postoperative external beam irradiation in a rat model. The model consisted of a rectangular full-thickness skin graft raised and reapplied to its original bed on the dorsum of each rat. Five groups of adult male Sprague-Dawley rats (n = 8 per group) were established. Group A was the control group and was not given postoperative irradiation. Groups B, C, D, and E received postoperative unfractionated cobalt60 irradiation 4 weeks after grafting for a total dose of 15, 20, 25, or 30 Gy, respectively. Weekly skin-graft evaluation was performed for the 4 weeks after irradiation (8 weeks after surgery) by measuring areas of graft loss using computerized planimetry. After the animals were killed, histologic samples were obtained from normal unirradiated skin and from both intact and ulcerated skin-graft sites. Graft loss after irradiation of < or = 20 Gy was similar to that of the unirradiated controls. Occurring as early as 1 week after treatment, a two-fold increase in graft ulceration was observed with doses of > or = 25 Gy (p = 0.0007). Only partial healing of ulcerations was noted by the fourth week after treatment. Histologic changes associated with the irradiation of skin grafts using doses of 25 Gy or higher included hyaline degeneration, fibrinoid necrosis, telangiectasia, and edema. Granulation tissue predominated as a mechanism of healing in areas of graft ulceration. The intensity of inflammatory cell infiltrate did not correlate with radiation dose. The authors concluded that postoperative, unfractionated irradiation can induce skin-graft loss at doses of 25 Gy or higher. Fractionated irradiation or longer intervals between grafting and irradiation may increase skin-graft tolerance; however, further studies are warranted.

Animals↗

PubMed1999

Comparison of kidney weight and volume to selected anatomical parameters in the adult female rhesus monkey (Macaca mulatta).

In this study, the normal distribution of renal weight and volume was determined and the correlation between the weight and volume and various skeletal measurements taken from radiographs and at necropsy was assessed. Values from 136 female monkeys with complete data (including all bone, radiographic, and kidney measurements) were analyzed. The mean kidney weight was 13 g with a standard deviation (SD) of 2 g. The mean kidney volume was 12 ml, SD 2 ml. The estimation of kidney weight and volume from bone length, age, or body weight was not reliable according to statistical analysis of our data. We did find that all apparently normal adult female rhesus monkeys typically have similar sized kidneys. This information is useful in that it reduces concerns about consistency in experimental subjects.

Animals↗