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Biomedical subjects

G A Wood

Publications and source records attributed to G A Wood.

At least 19 recordsLinked to original sources
PubMed2001

Resistance of Copenhagen rats to hepatocarcinogenesis does not involve T-cell immunity.

Previously, we have shown that Copenhagen (Cop) rats are highly resistant, compared with susceptible F344 rats, to the growth of glutathione S-transferase 7-7 (GST 7-7) positive preneoplastic liver lesions following treatment with a modified resistant hepatocyte (RH) protocol. Donryu rats, a strain with a level of susceptibility similar to F344, have a reduced T-cell response compared with the closely related, but highly resistant, DRH rat. Cop and DRH rats share several characteristics in their resistance to preneoplastic liver lesion growth and this study, therefore, was designed to examine whether T-cells play a role in Cop resistance. Cop rats were crossed with an athymic (nude) rat to produce F1s that were then interbred to produce F2 animals, some of which were nude with a partial Cop background. A comparison of the susceptibility of nude F2 animals and their euthymic (non-nude) littermates allowed us to determine what role, if any, T-cells play in Cop resistance. We treated 11 Cop, 11 F344, 19 nude F2s, and 18 non-nude F2s with diethylnitrosamine (DEN), followed 3 weeks later by a modified RH protocol. As expected, F344 rats were highly susceptible, having 41.9 +/- 3.3% (mean +/- SEM) of their liver section areas occupied by GST 7-7-positive lesions and Cop rats were highly resistant, having only 4.7 +/- 1.1% of their liver section areas occupied by lesions. Both nude and non-nude F2s were, like Cop rats, highly resistant (1.8 +/- 0.29 and 2.7 +/- 0.45%, respectively). These results show that T-cells are unnecessary for Cop rat resistance, or only play a minor role, and that the nude parental strain is also likely to be resistant to the growth of preneoplastic liver lesions.

Animals↗
PubMed2001

Assessing future possible selves by gender and socioeconomic status using the anticipated life history measure.

This is a report from the first phase of a longitudinal study of the ways young adults imagine their future lives. The future possible selves of 223 18- and 19-year-old adults were examined using the Anticipated Life History measure (ALH), a psychological instrument prompting participants to describe their future life course from their 21st birthday until their death. When the ALH narratives were coded for presence/absence of life events, female participants were more likely to predict career choice, marriage, children, divorce, and death of spouse than their male counterparts; when coded for psychological qualities, female participants demonstrated greater psychological complexity and awareness of future life role choices and conflicts. Participants with lower SES wrote ALH narratives with fewer altruistic acts, less awareness of life role complexity, and fewer anticipated conflicts and their resolutions than those with higher SES.

Adolescent↗
PubMed2001

Inheritance of resistance to promotion of preneoplastic liver lesions in Copenhagen rats.

Previously, we have shown that Copenhagen (Cop) rats are highly resistant to the induction of putative preneoplastic, glutathione S-transferase 7-7- (GST 7-7) positive liver lesions following treatment with a modified resistant hepatocyte (RH) protocol. The objective of this study was to determine if resistance is inherited in a dominant or recessive manner and to derive an estimate of the number of genetic loci involved. We crossed male and female Cop rats with F344 rats to produce F1 offspring. Backcross rats were generated using female F1 rats and either Cop or F344 males, resulting in B1c and B1f generations, respectively. The male rats from all these crosses were initiated with diethylnitrosamine (200 mg/kg) at 7 to 8 weeks of age and were promoted 3 weeks later with the RH protocol (2-acetylaminofluorene and a two-thirds partial hepatectomy). The rats were sacrificed 3 weeks after the partial hepatectomy and their livers were sectioned and stained for GST 7-7-positive lesions. The susceptibility of F1 rats was in between Cop and F344 rats, having 21.7% +/- 2.0% (mean +/- SEM) of their liver volume occupied by lesions versus 4.2% +/- 0.8% for Cop and 53.0% +/- 5.8% for F344 rats. As expected, B1c rats had a volume of liver occupied by lesions that was in between the F1 and Cop rats at 13.5% +/- 1.6%. Surprisingly, B1f rats were similar to B1c rats in their resistance (9.1% +/- 2.1%). These results point to a complex, polygenic inheritance pattern that can be explained by a minimum of four loci, one of which shows recessive epistasis.

Animals↗
PubMed2001

Matrix metalloproteinases-2 and 9 do not play a role in the growth of preneoplastic liver lesions in F344 rats.

Matrix metalloproteinases- (MMPs) 2 and 9 (gelatinases A and B) have been implicated in tumor invasion and metastasis, and recent studies have shown increased levels of these enzymes during recovery from partial hepatectomy (PH) in rats. F344 rats are highly susceptible to the growth of glutathione S-transferase 7-7- (GST 7-7) positive preneoplastic liver lesions promoted using the modified resistant hepatocyte (RH) protocol. Since the RH protocol consists of 2-acetylaminofluorene (2-AAF) followed by a PH, we reasoned that MMP-2 and -9 might be critical for the growth of lesions. Using gelatin zymography, we examined the expression of these enzymes in the livers of F344 rats treated with the RH protocol and sacrificed on Days 2, 4, 7, 14, and 21 after 2-AAF/PH. We found increases in both pro- and active MMP-2 and -9 over baseline levels, with the highest levels occurring on Day 7 post-PH. Also, a 54-kDa band, likely to be proMMP-1, was elevated in a pattern similar to MMP-2 and -9. In contrast to F344 rats, identically treated Copenhagen rats that are highly resistant to promotion of liver lesion growth using the RH protocol had significantly lower levels of proMMP-1 and -2. To test the importance of these MMPs to the growth of liver lesions, F344 rats that had been initiated with diethylnitrosamine were treated using the RH protocol. They then received either the MMP inhibitor batimastat (30 mg/kg, intraperitoneally) or vehicle alone daily from Day 3 to 20 post-PH and were sacrificed on Day 21. There were no differences in the percentage of liver volume occupied by GST 7-7-positive lesions (19.1 +/- 4.84 vs 19.4 +/- 3.31, treated versus vehicle, mean +/- SEM) or liver weight as a percentage of body weight (4.11% +/- 0.15 vs 4.07% +/- 0.18, treated versus vehicle, mean +/- SEM) between the treated and control groups. Treatment of rats with batimastat clearly did not affect lesion growth or liver regeneration following the RH protocol. These results suggest that increases in gelatinase expression during the RH protocol are a result of the promotional stimulus rather than a mechanism by which 2-AAF/PH causes lesion growth.

Alkylating Agents↗
PubMed2001

Complications following orthognathic surgery that required early surgical intervention: fifteen years' experience.

The aim of this study was to assess complications following various orthognathic surgical procedures that required early surgical intervention. This study was carried out on 821 patients who had undergone surgical treatment for correction of dentofacial deformities between 1985 and 2000. Only patients who required a second procedure to deal with immediate or early postoperative complications (i.e., those occurring within 4 weeks of surgery) were investigated in this study. Twelve patients underwent a second surgical procedure; 9 had undergone conventional osteotomy surgery, and 3 had undergone distraction osteogenesis. Three Le Fort I cases had to be further impacted and repositioned, and 4 vertical subsigmoid osteotomies had to be reexplored. The details of the complications are presented, and possible methods by which these problems could be reduced and/or prevented are discussed.

Adolescent↗
PubMed2000

Induction of hepatic insulin-like growth factor binding protein-1 (IGFBP-1) in rats by dietary n-6 polyunsaturated fatty acids.

The insulin-like growth factors (IGFs) are mitogenic polypeptides that have been linked to a variety of normal physiological processes as well as neoplasia. Overexpression of several components of the IGF system is associated with hepatocarcinogenesis in humans and rodents. In rat liver, diets rich in n-6 polyunsaturated fatty acid (PUFA) enhance the development of preneoplastic lesions and tumors. Therefore, the objective of this study was to determine the effect of these dietary fatty acids on the hepatic expression of the various components of the IGF system. The mRNA levels of IGF-1 and the type 1 receptor were not different in livers of rats fed a diet containing 20% corn oil (CO) compared with those fed 5% CO. Analysis of the IGF binding proteins revealed that insulin-like growth factor binding protein-1 (IGFBP-1) levels were altered by the amount and type of dietary fat. A 2.5-fold induction of IGFBP-1 mRNA occurred within 1 week after the animals were fed the 20% corn oil diet compared with those fed 5% CO and was further enhanced to over 6-fold after 1 month. Furthermore, IGFBP-1 protein was only detectable in the livers of animals fed the 20% CO diet. Induction of IGFBP-1 mRNA (4.5-fold) also occurred in rats fed a high-fat diet containing safflower (rich in n-6 PUFAs) compared with those fed a high-fat diet containing menhaden oil (rich in n-3 PUFAs). The induction of IGFBP-1 mRNA was independent of serum insulin levels and the development of insulin resistance. Since IGFBP-1 mRNA is upregulated in regenerating liver, we reasoned that the induction of IGFBP-1 mRNA may be associated with an increase in cell proliferation; however, no difference was observed in the hepatic labeling index of rats fed the 20% CO compared with the 5% CO diet. In summary, these studies show a striking induction by dietary n-6 PUFAs of hepatic IGFBP-1, a protein that has been implicated in liver cancer development.

Animals↗
PubMed1999

Cyclin D1 expression during rat mammary tumor development and its potential role in the resistance of the Copenhagen rat.

BACKGROUND: Resistance to mammary tumorigenesis in Copenhagen rats is associated with loss of early preneoplastic lesions known as intraductal proliferations. The cause of this disappearance, however, is unknown. RESULTS: There were no differences in the numbers of lesions in mammary whole-mounts prepared from Copenhagen or Wistar-Furth rats at 20 or 30 days after N-methyl-N-nitrosourea treatment, but at 37 days there were significantly fewer lesions in Copenhagen glands. Furthermore, lesions in Copenhagen glands were exclusively intraductal proliferations, whereas in Wistar-Furth glands more advanced lesions were also present. Immunohistochemical staining showed frequent cyclin D1 overexpression in Wistar-Furth lesions at 37 days, but not in Copenhagen lesions. There were, however, no differences in p16INK4a protein expression, bromodeoxyuridine labeling and apoptotic indices, or mast cell infiltration between Copenhagen and Wistar-Furth lesions at any time. CONCLUSIONS: Overexpression of cyclin D1 in preneoplastic lesions may be important in the development of mammary tumors in susceptible rats, although this overexpression does not appear to cause significant changes in cell kinetics. Furthermore, the low levels of cyclin D1 expression in Copenhagen intraductal proliferations may play a role in the resistance of these rats to mammary tumorigenesis.

Animals↗
PubMed1999

Resistance to the promotion of glutathione S-transferase 7-7-positive liver lesions in Copenhagen rats.

Previously, we have shown that Copenhagen (Cop) rats are highly resistant to the induction of putative preneoplastic, glutathione S-transferase 7-7 (GST 7-7)-positive liver lesions following treatment with a modified resistant hepatocyte protocol. The objective of the current study was to establish the time course for the development of resistance and examine potential resistance mechanisms in Cop rats using F344 rats as susceptible controls. Male Cop and F344 rats (n = 25), 7-8 weeks of age, were initiated with diethylnitrosamine (200 mg/kg) and promoted 3 weeks later with four doses of 2-acetylaminofluorene (20 mg/kg) and a 2/3 partial hepatectomy (PH). Groups of rats from each strain were killed on days 2, 4, 7, 14 and 21 post-PH, 2 h after receiving bromodeoxyuridine. Cop livers contained similar numbers of GST 7-7-positive lesions to F344 livers on days 2 and 4 post-PH. The percent volume of liver occupied by these lesions did not differ between the strains on days 2, 4 and 7 post-PH. On day 14, however, approximately 29% of the liver volume in F344 rats was occupied by lesions, whereas in Cop rats this was significantly less (approximately 9%, P < 0.001). On day 21, lesions occupied approximately 58% of F344 rat livers and only approximately 6% of Cop livers. Despite these differences, the labeling index of hepatocytes was not significantly different between the strains at any time point, either within lesions or within surrounding normal liver. Furthermore, the apoptotic indices were not different between the strains at any time. However, differences were found in the extent of lesion remodeling (redifferentiation) and in the pattern of oval cell response following PH in Cop livers. By day 14 post-PH, approximately 76% of Cop liver lesions showed evidence of remodeling, compared with only approximately 14% of F344 lesions. The oval cell response to PH was equivalent in the two strains up to day 4 post-PH but by day 7, in F344 livers there was extensive migration of these cells into the liver parenchyma, whereas in Cop livers, the response remained localized to the portal regions. These results suggest that Cop resistance occurs at the promotion stage and not the initiation stage of carcinogenesis. Resistance appears not to be due to a lower proliferation rate nor to a higher apoptotic rate within Cop lesions. Precocious remodeling and/or a diminished oval cell response, however, may contribute to the resistance of Cop rats to the growth of GST 7-7-positive hepatic lesions.

2-Acetylaminofluorene↗
PubMed1999

The benefits of wearing a compression sleeve after ACL reconstruction.

PURPOSE: It was the purpose of the present study to examine the possibility of increased muscle coordination after anterior cruciate ligament (ACL) reconstruction through the wearing of a compression sleeve. METHODS: Thirty-six patients were studied who had undergone unilateral ACL reconstruction at least 12 months previously. All subjects were required to perform a 10-cm standing drop jump from an elevated platform onto a force plate, to land on one leg, and thereafter maintain a one-legged balance for 25 s. This task was repeated three times without and three times with an elastic compression sleeve worn on the reconstructed limb. For analysis, the task was partitioned into a landing phase (150 ms), an adjusting phase (10s), and a balancing phase (10s). The peak impact loadings were measured in each direction (Fx, Fy, and Fz) during landing, while force-time integrals (intFz, intFy, and intFz) and root mean square (RMS) error of these forces were calculated for the adjusting and balancing phases. The path length and RMS of the center of pressure coordinates (Ax and Ay) were obtained for the adjusting and balancing phases combined. RESULTS: Drop landings with the bandage produced significantly larger (P < 0.001) peak ground reaction forces in the vertical and anteroposterior direction, suggesting increased subject confidence in their knee. Wearing the knee bandage also enabled the patients to reduce all measured parameters in the anteroposterior direction (rmsFx, intFx, rmsAx) during both the adjusting and balancing phases (P < 0.001 ). A significant reduction in the center of pressure path length further indicated an enhanced steadiness during the one-legged stance. CONCLUSIONS: It was concluded that a compression sleeve improved the total integration of the balance control system and muscle coordination.

Adult↗
PubMed1998

Bowel motility after enterocystoplasty.

OBJECTIVE: To determine whether the distension of bowel-augmented bladders during filling and urine storage stimulates gastrointestinal peristalsis, resulting in diarrhoea and increased bowel frequency. PATIENTS AND METHODS: Five patients with symptomatic diarrhoea occurring after enterocystoplasty were studied; all had undergone bladder augmentation using ileum or colon at least 6 months previously. Using bowel frequency charts and colonic transit-time studies, their bowel function was assessed over 6 days while patients self-catheterized 4-hourly. This was repeated when the patient's bladders were decompressed with an indwelling catheter, and the results before and after bladder decompression compared. RESULTS: One patient showed a significant increase in colonic transit time, from 44.4 to 57.6 h, a decrease in the percentage of liquid motions from 50% to 42.8% and a corresponding small decrease in bowel frequency with bladder decompression. One patient reported an increase in liquid stools, but there was a minor decrease in colonic transit time. The remaining three patients showed no improvement with bladder decompression. When data were combined and analysed using Student's paired t-test, there were no significant changes in colonic transit time, bowel frequency and diarrhoea stools with bladder decompression. CONCLUSIONS: Eliminating bladder distension and hence distension of the incorporated bowel segment in reconstructed bladders has no impact on bowel motility.

Adult↗
PubMed1997

Resistance to chemically-induced mammary tumors in Copenhagen X nude-derived F2 athymic rats: evidence that T-cell immunity is not involved in Copenhagen resistance.

Resistance to chemically-induced mammary tumors in the Copenhagen rat is well defined, but the mechanism of resistance has yet to be determined. We have tested whether or not Copenhagen rat resistance is dependent on T-cells, since several lines of evidence supported an involvement of the immune system. We crossed Copenhagen rats with an athymic nude rat to produce F1s, that were interbred to produce F2 animals, some of which were athymic with partial Copenhagen rat background. A comparison of the mammary tumor incidences between the nude athymic F2 animals and their non-nude littermates allowed us to determine what role, if any, T-cells played in resistance. Following treatment with N-methyl-N-nitrosourea, we observed no difference in the tumor incidences between the two groups. Furthermore, the mammary tumor incidences in the F2 nude and non-nude animals was almost zero. These results indicate that T-cells are not involved in Cop resistance, and that nude rats are resistant to N-methyl-N-nitrosourea-induced mammary tumorigenesis.

Animals↗
PubMed1997

Resistance of Copenhagen rats to chemical induction of glutathione S-transferase 7-7-positive liver foci.

Copenhagen (Cop) rats are completely resistant to the chemical induction of mammary adenocarcinomas, but their susceptibility to hepatocarcinogenesis is virtually unknown. Rat liver is a well-characterized and easily manipulated tissue in which to study carcinogenesis. Therefore, if Cop rats are resistant to hepatocarcinogenesis, studies into resistance mechanisms may be feasible. Male Cop and F344 rats, 7-8 weeks old, were initiated using either N-nitrosodiethylamine (DEN) (200 mg/kg, i.p.) or a two-thirds partial hepatectomy (PH) followed by N-methyl-N-nitrosourea (MNU) (60 mg/kg, i.p.). The rats were then promoted using a modified resistant hepatocyte (RH) protocol (a combination of four doses of 2-acetylaminofluorene (2-AAF) and a single dose of CCl4 that provides a selective mitotic stimulus for initiated cells). Six weeks after initiation the rats were killed and liver sections were stained for glutathione S-transferase 7-7 (GST 7-7), a marker for putative preneoplastic hepatocytes. Cop rats were found to be highly resistant, having a approximately 9- and approximately 27-fold smaller percentage of liver area occupied by GST 7-7-positive foci than susceptible F344 rats following initiation by DEN and MNU respectively. Furthermore, gross liver nodules did not form in any of the Cop rats, whereas all F344 rat livers contained nodules. Hepatic necrosis caused by DEN during initiation, and CCl4 during promotion is necessary to stimulate compensatory hepatocyte division. We demonstrated that these agents do indeed increase serum transaminase levels and produce histologic evidence of necrosis in Cop rats. In order for liver foci to grow rapidly in the RH protocol, the surrounding normal hepatocytes must be mito-inhibited by 2-AAF. We found that the degree of mito-inhibition of normal hepatocytes by 2-AAF is the same in Cop and F344 rats. These results show that the Cop rat is highly resistant to the chemical induction of putative preneoplastic liver foci and nodules.

2-Acetylaminofluorene↗
PubMed1997

Joint load considerations in total knee replacement.

Estimates of knee joint loadings were calculated for 12 normal subjects from kinematic and kinetic measures obtained during both level and downhill walking. The maximum tibiofemoral compressive force reached an average load of 3.9 times body-weight (BW) for level walking and 8 times BW for downhill walking, in each instance during the early stance phase. Muscle forces contributed 80% of the maximum bone-on-bone force during downhill walking and 70% during level walking whereas the ground reaction forces contributed only 20% and 30% respectively. Most total knee designs provide a tibiofemoral contact area of 100 to 300 mm2. The yield point of these polyethylene inlays will therefore be exceeded with each step during downhill walking. Future evaluation of total knee designs should be based on a tibiofemoral joint load of 3.5 times BW at 20 degrees knee flexion, 8 times BW at 40 degrees and 6 times BW at 60 degrees.

Adult↗
PubMed1996

Does hyperbaric oxygen have a role in the management of osteoradionecrosis?

A retrospective study of 12 episodes of osteoradionecrosis treated with hyperbaric oxygen (HBO) in 11 patients was carried out. The cases had been previously treated by more conventional methods including surgery, unsuccessfully. All the cases treated by HBO had a successful outcome, although 83% of the patients required concomitant surgery to remove necrotic bone. The costs and contra-indications for hyperbaric oxygen therapy are discussed.

Contraindications↗
PubMed1995

[The anterior cruciate ligament, an important structure of the knee joint].

The anterior cruciate ligament (ACL) is a crucial structure for a normal kinematic of the knee joint. Its rupture has been thought to present the initiation of a sequel leading to secondary damage of the meniscus and finally to osteoarthritis. Diagnosis of an ACL rupture is based on the history as well as on the physical examination. A positive Lachman-sign is diagnostic for an ACL lesion. The question whether an ACL rupture should be operated or not must be decided individually and is based on the demands of the patient. Conservative treatment includes rigorous physical therapy emphasizing strengthening exercises of the hamstrings and the gastrocnemius muscles as well as prorioceptive training. The indication for reconstruction is given, should instability persist. The timing of the operation is important for the outcome. This paper presents an overview of the literature including the rehabilitation program and a diagnostic concept used by the authors.

Anterior Cruciate Ligament↗
PubMed1995

Orbital subperiosteal abscess and blindness complicating a minimally displaced zygomatic complex fracture.

A case of orbital subperiosteal abscess (SPA) complicating a minimally displaced zygomatic complex (ZMC) fracture is reported and the aetiology and management of this potentially life-threatening condition is discussed. The value of CT scanning in staging orbital infection and determining the site of the abscess and involved paranasal sinuses is emphasised. The correct interpretation of a lateral skull radiograph with the patient brow up may have lead to earlier diagnosis and treatment.

Abscess↗
PubMed1995

Kinematic and kinetic comparison of downhill and level walking.

Kinematic and kinetic data were collected from 12 healthy subjects whilst they performed both downhill and level walking at a controlled cadence. A ramp of 6 m length and a gradient of -19% was used for downhill walking and this incorporated the same force platform that was used for level walking. Planar net joint moments and mechanical power at the ankle, knee, and hip joints were calculated for the sagittal view using force platform and video records based on standard inverse dynamics procedures. On the basis of differences in ankle, knee, and hip joint kinematics the ankle joint was seen to compensate for the gradient at push off and during the swing, the knee joint from early stance through until early swing phase, and the hip joint from early swing through until the early stance phase. The major differences in joint moments and muscle mechanical power were seen in the knee and ankle joint. Whereas peak moments and muscle power were much higher for downhill walking in the knee joint, these measures were significantly smaller at the ankle joint. Hip joint moments and muscle power estimates were only slightly larger for downhill walking. These data explain well the problems that patients with patellofemoral pathology and anterior cruciate ligament (ACL) deficiency encounter with downhill walking, and the muscle soreness experienced by mountain trekkers. RELEVANCE: Biomechanical estimates of musculoskeletal loadings in gait are invariably derived from laboratory studies of walking over a level surface. In this study comparisons were made between downhill and level walking in order to appreciate more fully the increased loadings on the lower extremity under more stressful but not atypical conditions. The data so derived provide the necessary basis for the prediction of loadings on specific muscle/joint structures and can serve as a foundation for exercise prescription with patients recovering from injury or orthopaedic surgery.

Journal Article↗