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Biomedical subjects

M Cook

Publications and source records attributed to M Cook.

At least 73 records · Page 4Linked to original sources
PubMed1996

Changes in applicator position with fractionated high dose rate gynaecological brachytherapy.

The reproducibility of high dose rate gynaecological brachytherapy applicator position in the same patient at repeated treatments has been studied. Measurements on antero-posterior and lateral radiographs to detect relative positions of tube and ovoid to the bony pelvis, bladder and rectum were made. Major variations within the same patient in craniocaudal positioning of the applicators and in antero-posterior movement was seen. The position of the anterior rectal wall was found to move a median of 10.5 mm (range, 0-22) in relation to the ovoid source between first and second insertions. These changes can be accounted for in differences in technique between first and second insertion and in particular the use of posterior vaginal packing and exterior clamping. The importance of individual dosimetry for each high dose rate insertion is clear with major differences in dosimetry to critical normal structures having been found.

Brachytherapy↗
PubMed1996

Active minimisation of radiation scatter during breast radiotherapy: management implications for young patients with good-prognosis primary neoplasms.

BACKGROUND AND PURPOSE: Radiotherapy is used to reverse or prevent local tumour growth but is also a carcinogen in its own right. A recent audit of post-radiotherapy second malignancies in this institution revealed a striking preponderance of tumours originating near the outside edge of the treatment field. Since this finding suggests the existence of a critical subtherapeutic dose range predisposing to tumourigenesis, we attempted to define and reduce this radiation scatter dose. MATERIALS AND METHODS: We undertook a dosimetric review of 6 MV scatter from a linear accelerator in sites matching the putative tumourigenic region, and then extended this analysis to patients and tissue phantoms. RESULTS: A wide range of radiation scatter doses was confirmed-for example, doses 3 cm from the field edge varied from 1.7 to 22% of the therapeutic dose depending upon the field parameters. Scatter doses were then assessed in a sample of eight patients undergoing standard breast radiotherapy. Contralateral breast sites 4-12 cm from the midline received 4-10% of the therapeutic dose, or 200-500 cGy for a 50 Gy treatment, approximating historical estimates of the tumourigenic range. The deep component of this scatter dose from medial field breast irradiation was reduced 19% simply by replacing the 15 degrees medial tangential field wedge with a 30 degrees lateral wedge. Other manoeuvres which reduced contralateral breast dose by up to 46% included making the posterior field edges co-planar and shielding the breast during medial field irradiation. CONCLUSIONS: These results suggest that the risk of radiogenic second malignancies could be significantly decreased by careful attention to the treatment details. Greater awareness of these measures may prove particularly relevant to the conservative management of young patients with good-prognosis breast neoplasms such as ductal carcinoma in situ.

Breast↗
PubMed1996

A nitric oxide synthesis inhibitor (L-NAME) reduces licking behavior and Fos-labeling in the spinal cord of rats during formalin-induced inflammation.

Formalin injected subcutaneously into the hindpaw of the rat produces an animal model of inflammation that exhibits a phasic component and a tonic component of pain. We evaluated the effects of a nitric oxide synthase inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME), on a formalin-induced behavior, hindpaw licking, and on Fos-labeling of nuclei in the fifth lumbar spinal segment. Our results demonstrated that pretreatment with intrathecal doses of 0.3 and 1.0 mg of L-NAME significantly reduced licking behavior associated with injection of formalin into the left hindpaw of the rat. In addition, these same doses of L-NAME reduced formalin-induced Fos-labeling in the ipsilateral dorsal gray matter (as compared to the contralateral gray matter). Qualitative assessment suggested that the reduction in labeling occurred primarily in the superficial dorsal horn. The stereoisomer, D-NAME, administered at the same doses had little to no effect on either formalin-induced licking or Fos-labeling. Finally, our results revealed that total licking time was related to Fos-labeling. Rats that spent less time licking the hindpaw exhibited a smaller increase in Fos-labeling. Our results suggest that the production of nitric oxide is associated with licking behavior resulting from formalin injection into the hindpaw of rats. Our results also suggest that the production of nitric oxide and Fos are associated. Indeed, these substances may be involved in spinal pathways associated with nociception.

Amino Acid Sequence↗
PubMed1996

In-vitro metabolic studies of tacrolimus using precision-cut rat and human liver slices.

The objective of this study was to investigate the in-vitro metabolism of tacrolimus in liver slices from rats and humans. [14C]Tacrolimus (2 or 20 microM) was incubated with precision-cut human and rat liver slices in 12-well plates for up to 12 h. Concentrations of tacrolimus and metabolites were determined by high-performance liquid chromatography (HPLC) radiochromatography. The 13-O-demethylated tacrolimus metabolite (M-I) was the major oxidative metabolite in both rat and human liver slices. The other primary metabolites of tacrolimus (M-II, M-III, and M-IV) were not seen in either species. Unidentified peaks, which eluted early in the HPLC system, were probably due to secondary or conjugated metabolites. The eluate had no pharmacological activity. The finding that M-I was the major tacrolimus metabolite in both human and rat liver slice preparations is consistent with previous studies of rat and human liver microsomes.

Adolescent↗
PubMed1996

A comparison of immunohistochemistry, two-color immunofluorescence, and flow cytometry with cell sorting for the detection of micrometastatic breast cancer in the bone marrow.

A significant percentage of women with primary breast cancer have micrometastatic disease in the bone marrow. Bone marrow involvement may be an adverse prognostic factor, and more aggressive therapy may be indicated for these patients. There are a number of different techniques and antibodies used to detect tumor cells in the bone marrow. We used the same panels of four antibreast cancer antibodies and compared three immunodetection techniques: two-color immunofluorescence, immunohistochemical staining, and fluorescence-activated cell sorting with cytologic examination of the sorted cells. The two-color immunofluorescence technique was superior and consistently detected one tumor cell contaminating one million normal bone marrow cells and had no reactivity with normal bone marrow.

Bone Marrow Neoplasms↗
PubMed1996

Expression of basic fibroblast growth factor in desmoplastic melanoma.

Basic fibroblast growth factor (bFGF) is an established growth factor for melanocytes and a potent angiogenic factor. The expression of bFGF was investigated in 23 desmoplastic melanomas. (DM) (12 males, median age 64 years, and 11 females, median age 54 years) by immunostaining of formalin-fixed, paraffin-embedded sections with high-affinity purified antibody raised against recombinant human bFGF (Scios Nova, Inc.). The tumors were characterized by level II invasion in 1 case (5%), level IV invasion in 11 cases (48%), level V invasion in 8 cases (35%), and indeterminate in 3 cases. bFGF expression was observed in 22 of 23 tumors (95%), either immune localized to tumor cell nuclei in 17 of 22 tumors (77%), or to the cytoplasm of tumor cells in 5 of 22 tumors (23%). Also in these cases, bFGF was strongly expressed in the nuclei of vascular endothelial cells. Maximal expression was noted in the peripheral blood vessels of 20 tumors (91%) versus intratumoral vessels of 13 DM (59%). In conclusion, the expression of predominantly nuclear bFGF by tumor cells in DM suggests a role in mediating the desmoplastic phenotype. In addition, the localization of bFGF to vascular endothelium, particularly at the periphery of the tumor, may be relevant to tumor angiogenesis.

Adult↗
PubMed1996

The role of HLA class II genes in insulin-dependent diabetes mellitus: molecular analysis of 180 Caucasian, multiplex families.

We report here our analysis of HLA class II alleles in 180 Caucasian nuclear families with at least two children with insulin-dependent diabetes mellitus (IDDM). DRB1, DQA1, DQB1, and DPB1 genotypes were determined with PCR/sequence-specific oligonucleotide probe typing methods. The data allowed unambiguous determination of four-locus haplotypes in all but three of the families. Consistent with other studies, our data indicate an increase in DR3/DR4, DR3/DR3, and DR4/DR4 genotypes in patients compared to controls. In addition, we found an increase in DR1/DR4, DR1/DR3, and DR4/DR8 genotypes. While the frequency of DQB1*0302 on DR4 haplotypes is dramatically increased in DR3/DR4 patients, DR4 haplotypes in DR1/DR4 patients exhibit frequencies of DQB1*0302 and DQB1*0301 more closely resembling those in control populations. The protective effect of DR2 is evident in this data set and is limited to the common DRB1*1501-DQB1*0602 haplotype. Most DR2+ patients carry the less common DR2 haplotype DRB1*1601-DQB1*0502, which is not decreased in patients relative to controls. DPB1 also appears to play a role in disease susceptibility. DPB1*0301 is increased in patients (P < .001) and may contribute to the disease risk of a number of different DR-DQ haplotypes. DPB1*0101, found almost exclusively on DR3 haplotypes in patients, is slightly increased, and maternal transmissions of DRB1*0301-DPB1*0101 haplotypes to affected children occur twice as frequently as do paternal transmissions. Transmissions of DR3 haplotypes carrying other DPB1 alleles occur at approximately equal maternal and paternal frequencies. The complex, multigenic nature of HLA class II-associated IDDM susceptibility is evident from these data.

Adolescent↗
PubMed1996

[Technical options of renal transplant in the absence of a viable ilio-caval venous circuit. Presentation of a case and review of the literature].

Congenital absence of useful ilio-caval venous segment is a very infrequent congenital anomaly and makes unfit grafting of a kidney transplant in iliac fossa. We report the case of a 18 years old male affected by this abnormality who was transplanted in intraabdominal situation. We review technical alternatives offered by the literature.

Adolescent↗
PubMed1995

Leukemia translocation gene, PLZF, is expressed with a speckled nuclear pattern in early hematopoietic progenitors.

The PLZF gene was discovered by studying a rearrangement of the RAR alpha locus in a patient with acute promyelocytic leukemia and a t(11;17) chromosomal translocation. To understand further the potential role(s) of the PLZF gene product in hematopoiesis, we have examined its expression levels in a variety of murine tissues and in established cell lines that are representative of various stages of myeloid and lymphoid development. We show that murine PLZF(mPLZF) is expressed at the highest levels in undifferentiated, multipotential hematopoietic progenitor cells and that its expression declines as cells become more mature and committed to various hematopoietic lineages. Data obtained with established cell lines are corroborated by results showing the lack of human PLZF protein expression in mature peripheral blood mononuclear cells and high PLZF levels in the nuclei of CD34+ human bone marrow progenitor cells. Interestingly, unlike many transcription factors, PLZF protein in these cells possesses distinct punctate nuclear distribution, suggesting its compartmentalization in the nucleus. Taken together, our data suggest a role for PLZF protein in early hematopoiesis and the requirement of downregulation of its expression for proper differentiation of most hematopoietic lineages.

Amino Acid Sequence↗
PubMed1995

Preservation of autoregulatory cerebral vasodilator responses to hypotension after inhibition of nitric oxide synthesis.

Effects of inhibition of nitric oxide (NO) synthesis on the cerebrovascular autoregulatory vasodilator response to hypotension were studied in conscious rats. Cerebral blood flow (CBF) was determined with [14C]iodoantipyrine in a saline-treated control group and in three groups following inhibition of NO synthase activity by twice daily intraperitoneal injections of 50 mg/kg of NG-nitro-L-arginine methyl ester (L-NAME) for four days. In the saline-control group (n = 8) and in the L-NAME-treated Group (a) (n = 8) CBF was determined while systemic mean arterial blood pressure (MABP) remained at its resting level (means +/- S.D., 128 +/- 6 and 151 +/- 11 mmHg, respectively). In the other groups CBF was determined after MABP was reduced by blood withdrawal to 118 +/- 9 and 88 +/- 8 mmHg in Groups (b) (n = 8) and (c) (n = 8), respectively. Despite the elevated MABP, global CBF was significantly lower in L-NAME-treated Group (a) than in the saline-controls (P < 0.005), indicating cerebral vasoconstriction resulting from inhibition of NO synthesis. Global CBF was not significantly reduced further in the two groups with hypotension. Local CBF in the hypotensive rats showed no significant reductions below values in L-NAME-treated control rats (Group (a)) in 31 of 32 brain structures; the only exception was in the auditory cortex of the severely hypotensive rats (Group (c)). The autoregulatory mechanism for cerebral vasodilatation to compensate for reduced arterial blood pressure is maintained following inhibition of NO synthesis.

Animals↗
PubMed1995

Expression of the zinc-finger gene PLZF at rhombomere boundaries in the vertebrate hindbrain.

To investigate the potential biological role(s) of the PLZF gene, discovered as a fusion with the RARA locus in a patient with acute promyelocytic leukemia harboring a t(11;17) chromosomal translocation, we have isolated its murine homologue (mPLZF) and studied its patterns of developmental expression. The levels of mPLZF mRNAs increased perinatally in the liver, heart, and kidney, but with the exception of the heart, they were either absent or very low in the adult tissues. In situ analysis of mPLZF expression in mouse embryos between 7.0 and 10.5 days of development revealed that mPLZF mRNAs and proteins were coexpressed in spatially restricted and temporally dynamic patterns in the central nervous system. In the hindbrain region, a segmental pattern of expression correlated with the development of the rhombomeres. From 9.0 days of development, starting first in rhombomeres 3 and 5, there was an ordered down-regulation of expression in the center of each rhombomere, so that 1 day later elevated levels of mPLZF mRNAs and proteins were restricted to cells surrounding the rhombomeric boundaries. The chicken homologue of the PLZF gene, which we have also cloned, demonstrated a similar segmental pattern of expression in the hindbrain. To date, PLZF represents the only example of a transcription factor with elevated expression at rhombomeric boundaries. The high degree of evolutionary conservation between the patterns of PLZF expression during mammalian and avian central nervous system development suggests that it has an important functional role in the regionalization of the vertebrate hindbrain, potentially regulating boundary cell interactions.

Amino Acid Sequence↗
PubMed1995

Effects of growth hormone on kidney function in pediatric transplant recipients.

Recent evidence suggests that treatment with recombinant human growth hormone (rhGH) after a successful kidney transplant improves the growth rate of children with short stature. We prospectively investigated eight children (6 boys, 2 girls), focusing on acute rejection episodes and changes in serum creatinine levels during rhGH treatment. The children (mean age 11.6 +/- 3.4 years) received rhGH daily (0.04-0.05 mg/kg subcutaneously). Seven patients completed at least 12 months (20 +/- 8 months) of rhGH treatment. Their mean serum creatinine level was 1.3 +/- 0.7 mg/dl 12 months before, and increased to 3.4 +/- 4.2 mg/dl after 12 months of rhGH treatment, but did not achieve statistical significance (P = 0.06). Their mean calculated glomerular filtration rate was 58 +/- 20 ml/min per 1.73 m2 12 months before, and decreased to 38 +/- 21 ml/min per 1.73 m2 after 12 months of rhGH treatment, but did not achieve statistical significance (P = 0.08). Of the seven patients, two developed acute rejection after 5 and 6 rejection-free years; three lost their grafts and returned to dialysis. These preliminary observations describe untoward renal events in children receiving rhGH treatment after a kidney transplant.

Adolescent↗
PubMed1995

Relationship of helmet use and head injuries among motorcycle crash victims in El Paso County, Colorado, 1989-1990.

A case-control study was conducted in El Paso County, Colorado to estimate differences in risk of head injury among persons in motorcycle crashes who were or were not wearing helmets. There were 71 cases, motorcyclists with head injuries from crashes, and 417 controls, motorcyclists in crashes without head injuries. Motorcyclists not wearing helmets were 2.4 times as likely to sustain head injuries (95% confidence limits: 1.23, 4.70) than motorcyclists wearing helmets. This odds ratio was adjusted for age and crash characteristics, using logistic regression. Alcohol intoxication and severity of motorcycle damage were also associated with significantly elevated odds ratios related to sustaining a head injury.

Accidents, Traffic↗
PubMed1995

An illusion of relative motion dependent upon spatial frequency and orientation.

Observers scanned a stationary pattern comprising a tilted sine-wave grating completely surrounding another grating of similar spatial frequency but tilted in the opposite direction (Fig. 2). They reported an illusory "sliding" motion of the inset grating with respect to the surround grating and the effect was clearly strongest for angles between the gratings of less than 60 degrees and for spatial frequencies between 6-11 cpd. In a second experiment, a similar pattern was moved (2.0 deg/sec) either up or down for a presentation time of 167 msec. Simultaneously, the inset grating was drifted at different speeds in each of its two directions. Using the method of constant stimuli, it was shown that the relative motion illusion could be cancelled by physically drifting the grating in the opposite direction to the illusory movement. The illusion arises because there is a failure to integrate two motion signals into the single motion vector which characterises rigid motion.

Contrast Sensitivity↗