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Biomedical subjects

P Hamilton

Publications and source records attributed to P Hamilton.

At least 55 records · Page 3Linked to original sources
PubMed1996

Retinal vascular abnormalities. A rare complication of myelinated nerve fibers?

BACKGROUND: Myelinated nerve fibers of the retina occur in approximately 0.98% of the population. Although they are generally believed to be benign lesions, they occasionally are associated with ocular complications. METHODS: The authors report a series of six cases of myelinated nerve fibers complicated by retinal vascular abnormalities, three of which presented clinically as recurrent vitreous hemorrhage. The cause of the retinal vascular abnormalities remains unclear; however, from fluorescein angiography, it would appear likely that underlying inner retinal ischemia may be implicated. One patient with troublesome recurrent vitreous hemorrhage was treated with argon laser photocoagulation. RESULTS: These cases illustrate that although vascular abnormalities are a rare complication of myelinated nerve fibers, they can cause visual and diagnostic problems for these patients and their physicians. CONCLUSION: Although the authors' experience in treating these lesions is limited, they believe that in one treated case, argon laser photocoagulation was useful in halting recurrent vitreous hemorrhage.

Adult↗
PubMed1995

Basal cell adenocarcinoma of the submandibular gland.

Basal cell adenoma is a well recognized histopathologic variant of monomorphic adenoma of salivary gland, but in recent years there have been occasional reports of malignant basal cell tumors of major salivary glands. We present a case report of one such basal cell adenocarcinoma arising in the submandibular gland and discuss the differential diagnosis and distinction from a basal cell adenoma. We also review the published literature on basal cell adenocarcinoma. This is the first case of basal cell adenocarcinoma to be studied in detail by both immunohistochemistry and electron microscopy. There has been debate in the past as to the cell of origin of salivary gland basal cell tumors and specifically as to whether myoepithelial differentiation occurs in these tumors. The immunohistochemical and ultrastructural features of this case provide evidence for a dual population of ductal and myoepithelial cells. A flow cytometric analysis of nuclear deoxyribonucleic acid content showed the presence of DNA aneuploidy within one tissue block.

Adenocarcinoma↗
PubMed1995

A prospective study of emergent abdominal sonography after blunt trauma.

In North America, the role of emergent abdominal sonography [ultrasonography (US)] after blunt trauma requires further definition. The purpose of this prospective study was to compare US to the gold standards, diagnostic peritoneal lavage (DPL), and computed tomography (CT), in a population of adults after blunt trauma. In 206 adults who required either CT or DPL to assess possible abdominal injury, US was performed, before DPL or CT, and was aimed at the detection of intraperitoneal fluid. The mean Injury Severity Score and Glasgow Coma Scale score were 24.0 and 11.9, respectively. One hundred thirty-seven patients (67%) had CT and 69 (33%) had DPL. The positive and negative predictive values of US for intraperitoneal fluid were 90% and 97%, respectively. The sensitivity, specificity, and accuracy of US for free fluid were 81%, 98%, and 96%, respectively. Of the six false-negative USs, only one required surgery. The US examinations required 2.6 +/- 1.4 min. Emergent abdominal sonography is an accurate, rapid test for the presence of intraperitoneal fluid in adult blunt trauma victims and in these patients may prove valuable as a screening test for abdominal injury.

Abdominal Injuries↗
PubMed1995

Significance of intra-abdominal extraluminal air detected by CT scan in blunt abdominal trauma.

The purpose of this study was to determine the frequency and significance of computed tomographic (CT) scan-detected pneumoperitoneum in blunt abdominal trauma. We retrospectively reviewed 118 consecutive CT scans of the abdomen in blunt abdominal trauma patients (mean Injury Severity Score 24), performed at our Regional Trauma Unit over a 12-month period. Seven (5.9%) patients had intra-abdominal extraluminal air. None of these seven patients had evidence of bowel perforation at laparotomy (two) or on clinical follow-up (five). All seven had chest tubes in place before the CT scan. None of the seven patients were on mechanical ventilation at the time of CT scan. In the setting of blunt abdominal trauma pneumoperitoneum does not necessarily indicate hollow viscus injury. It frequently is secondary to other etiologies, especially dissection of interstitial air from the chest, as suggested in this study. The decision for laparotomy should be based on a combination of the clinical findings, CT scan results, or other diagnostic tests such as peritoneal lavage.

Abdominal Injuries↗
PubMed1994

Hydrochloric acid denaturation of colorectal tumour tissue infiltrated with bromodeoxyuridine.

The thymidine analogue, bromodeoxyuridine, is substituted into DNA during DNA synthesis and can be used to identify those cells which have passed through the S-phase of the cell cycle. Incorporated bromodeoxyuridine can be detected using anti-bromodeoxyuridine monoclonal antibodies which bind to the exposed bromodeoxyuridine in single-stranded DNA after a suitable denaturation step. Hydrochloric acid is the most commonly employed denaturation agent in bromodeoxyuridine monoclonal antibody methodologies. This preliminary study was to validate the hydrochloric acid denaturation step for colorectal tumour tissue infiltrated in vivo with bromodeoxyuridine. Standard immunohistochemistry and flow cytometric techniques using Bu20a were employed across a range of hydrochloric acid concentrations. Although high labelling indices were achieved using acid concentrations of 0.10 M HCl, the optimal hydrochloric acid concentration was not the same in all tumours. Sensitivity of DNA to hydrochloric acid denaturation should be carefully considered in bromodeoxyuridine methodologies using the monoclonal antibody Bu20a.

Antibodies, Monoclonal↗
PubMed1994

Nycthemeral profile of nonspectral heart rate variability measures in women and men. Description of a normal sample and two sudden cardiac arrest subsamples.

Heart rate variability (HRV), a noninvasive systemic index of the central autonomic nervous system, demonstrates considerable within-subject variability, including a strong systematic 24-hour nycthemeral (or less precisely, circadian) component. Recent interest in the timing of sudden cardiac arrest (SCA), especially the pronounced morning rise in sudden deaths, has motivated research into coincident dynamic phenomena in HRV indices of central autonomic nervous system activity. In this study, statistical (nonspectral) HRV measures (SD and %RR50) were summarized for consecutive 15-minute blocks from 24-hour Holter electrocardiogram tapes. Six subgroups were scrutinized: women and men respectively in three clinical strata (normal subjects [n = 85 women and 40 men], SCA with no current or prior myocardial infarction [MI] [n = 9 women and 31 men], SCA with old MI [n = 7 women and 48 men]). Significant nycthemeral effects were observable for all HRV measures in five of the six groups, with a dramatic fall in HRV during the hours of the morning with the highest phenomenologic incidence of SCA. Both strata of SCA subjects had much lower HRV than the normal subjects. This effect was strongest during the night-time hours, particularly for a purported index of vagal tone (%RR50). For reasons that are not known, the nine female SCA survivors who had no current or previous MI presented very distinct 24-hour patterns for the HRV measures studied. Twenty-four-hour profiles of short-term statistical HRV provide a rich field for the observation of within-subject adaptations of the central autonomic nervous system inputs to the heart in both normal and clinical subgroups.

Circadian Rhythm↗
PubMed1994

Contact diode laser cyclo-photocoagulation for refractory glaucoma. A pilot study.

Initial experience with non-contact diode cyclo-photocoagulation for refractory glaucoma has shown positive results. Diode laser irradiation applied via a contact probe results in greater transmission through the sclera and delivery of more energy to the ciliary body. A trial was performed to evaluate the effects of contact diode cyclo-photocoagulation. A total of 12 patients with glaucoma due to conditions such as central retinal vein occlusion were treated. A mean of 22 pulses (810 nm) with powers of up to 2 W and of 2 s duration were applied via a fibre-optic delivery system and a contact probe. The mean intra-ocular pressure dropped from 42.3 to 13.6 mmHg over 3 months. Four patients required retreatment. Three patients had side effects that included hyphaema, anterior fibrinous uveitis and pupil block. In conclusion, contact diode cyclo-photocoagulation had a significant ocular hypotensive action in the treatment of refractory glaucoma. As compared with non-contact diode cyclo-photocoagulation, the contact modality produced more marked non-therapeutic side effects.

Adult↗
PubMed1993

A language to describe the growth of neurites.

How can biological plasticity been added to a simulation of neuritic growth? Coming from this question, we have chosen a new access to simulate neuritic growth under the very aspect of meaningful and progredient development of single cells. Based on a specific description-language, we have set up a computer-program, to construct neurite-models and to simulate neuritic interaction during their development. Instead of using mathematical equations, we define various types of cytoskeletons by taking a specified graph grammar. Using this technique, we are able to define strings, combined with other influencing parameters, which allow the setting up of very naturally behaving artificial nervecells, in which distinct statistical variance and fixed rules as given in DNA operate together. In this paper, we want to discuss the underlying principles of the given grammar and to show some results from these computer-simulations, which enable us to study growth, development and other specific characteristics of neurites within a simulator in comparison to in vivo-experiments.

Animals↗
PubMed1993

In vitro BrdUrd incorporation of colorectal tumour tissue.

This study describes a novel in vitro method for the incorporation of the thymidine analogue, bromodeoxyuridine (BrdUrd), in fresh colorectal tumour tissue. Disaggregation by pronase, collagenase and DNAse resulted in high cell yields of viable single cell suspensions, representative of the original tumour, which could be infiltrated with BrdUrd. A modified ELISA identified optimal incubation times and BrdUrd concentrations. This technique has been used in preliminary studies to investigate two important areas intrinsic in the analysis of BrdUrd colorectal cell proliferation data: 1) to determine the effects of the individual constituents of the cell culture media, in particular glutamine, on BrdUrd incorporation in suspensions of colorectal cells and 2) to examine the denaturation step. This method will have wide applicability in investigations of cell proliferation status in both normal and diseased tissue.

Bromodeoxyuridine↗
PubMed1993

DNA densitometry of colorectal cancer.

DNA analysis was assessed by densitometry for 281 cases of colorectal adenocarcinoma. Detection of aneuploidy in a single case rose from 65% if one, to 92.5% when three or more sections, were analysed. Although aneuploid tumours had significantly larger nuclear areas than near diploid tumours (p = 0.009), densitometric measurements showed no association with clinicopathological variables. DNA content determined by densitometry was compared with that from flow cytometry on 465 tissue sections from 241 cases. Aneuploidy assessed by flow cytometry was significantly associated with that determined by densitometry (p < 0.01 for all comparisons), ploidy state being similar in 381 sections (82%, kappa = 0.63, p < 0.001), and 187 cases (77.6%, kappa = 0.57, p < 0.001). Univariate survival analysis showed that DNA densitometric variables had no significant association with survival in (a) all cases, (b) cases without lymph node metastases, or (c) cases without distant metastases. Multivariate regression analysis of densitometric and clinicopathological variables identified Dukes's stage, patient age, and tumour differentiation as the combination of variables most closely related to survival. Densitometric measurement of DNA content could not significantly improve on the prognostic model containing these three variables. It is concluded that, although the assessment of DNA content by densitometry is comparable with that of flow cytometry, conventional histological variables remain the best predictors of prognosis in colorectal cancer.

Adenocarcinoma↗
PubMed1993

Obtaining and evaluating data sets for secondary analysis in nursing research.

Secondary analysis of existing data offers many advantages to the nurse researcher. Data from large-scale studies may be reanalyzed and refined by secondary analysts with a fresh perspective, thus enhancing the original study's contribution to scientific knowledge. High-quality data can be obtained for comparatively little expenditure of time and money. The secondary analyst, however, must exercise care in evaluating and analyzing a data set to maximize the internal and external validity of the reanalysis. Because the secondary analyst's lack of involvement in data collection procedures may decrease insight into the original study's limitations, vigilant skepticism should accompany all phases of the research process in secondary data analysis, just as it should in all other research. Miller (1982) advised, "Begin by assuming the worst and seek out the same kinds of information about sample selection procedures, sample size, response rates, field procedures, and coding conventions that you would insist on if you were collecting your own data" (p. 722). By systematically evaluating potential data sets according to rigorous predetermined criteria, the nurse researcher can minimize the possible pitfalls inherent in secondary analysis. On the other hand, investigators who use secondary sources appropriately can make significant contributions to nursing science at less cost than that engendered by traditional research methods.

Data Collection↗
PubMed1993

The role of flow cytometry in carcinoma of the colon and rectum.

Flow cytometry was performed upon 312 patients with adenocarcinoma of the colon and rectum, satisfactory results being obtained with 275 (108 diploid, 130 aneuploid and 37 tetraploid). The proportion of nondiploid instances increased from 28 percent if one, to 80 percent when six specimens were assessed per patient. Reproducibility of the technique showed substantial agreement in the assessment of deoxyribonucleic acid ploidy (Kappa value equals 0.74). Increasing values of cells in the diving (G2/M) phase of the cell cycle were associated with little lymphocytic tumor infiltration (p = 0.0002) and extensive tumor fibrosis (p = 0.003). Univariate survival analysis revealed that, although diploid tumors tended to have a better prognosis than nondiploid tumors (p = 0.06), no flow cytometric variable was significantly related to survival. Flow cytometry similarly was not of prognostic value in instances without lymph node metastases or without distant metastases. Multivariate regression analysis of flow cytometric and clinicopathologic variables identified Dukes' stage, patient age and tumor differentiation as the combination of variables most closely related to survival. No flow cytometric variable could significantly improve on the prognostic model containing these three variables. It is concluded that conventional histologic variables remain the best predictors of prognosis in carcinoma of the colon and rectum.

Adenocarcinoma↗
PubMed1992

Seroprevalence of antibodies to the human immunodeficiency virus in dialysis workers: results of a multi-center study.

The Center for Devices and Radiological Health, in collaboration with the Department of Veterans Affairs Medical Center, Brooklyn, N.Y., conducted a multi-center, multi-institutional study of the seroprevalence of antibodies to the human immunodeficiency virus (HIV) among dialysis workers. Seven dialysis units and 112 dialysis workers participated in the study over a period of 2 years. Participation was limited to dialysis workers who, by questionnaire, denied non-occupational risk factors for HIV infection. The vast majority of the study participants were drawn from areas where the prevalence of HIV infection and AIDS cases are substantially greater than the national average. Study participants received the ELISA test for HIV antibodies. All 112 of the participants tested negative for HIV antibodies. These results are encouraging, as they failed to reveal unrecognized occupational transmission of HIV infection among dialysis workers.

HIV↗