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Biomedical subjects

G A Alexander

Publications and source records attributed to G A Alexander.

At least 19 recordsLinked to original sources
PubMed2001

Clinical validation of an artificial neural network trained to identify acute allograft rejection in liver transplant recipients.

Artificial neural networks (ANNs) are techniques of nonlinear data modeling that have been studied in a wide variety of medical applications. An ANN was developed to assist in the diagnosis of acute rejection in liver transplant recipients. We investigated the diagnostic accuracy of this ANN on a new data set of patients from the same hospital. In addition, we compared the diagnostic accuracy of the ANN with that of the individual input variables (alanine aminotransferase [ALT] and bilirubin levels and day posttransplantation). Clinical and biochemical data were collected retrospectively for 124 consecutive liver transplantations (117 patients) over the first 3 months after transplantation. Diagnostic accuracy was calculated using receiver operating characteristic (ROC) curve analysis. The ANN differentiated rejection from rejection-free episodes in the new data set over the first 3 months posttransplantation with an area under the ROC curve of 0.902 and sensitivity and specificity of 80.0% and 90.1% at the optimum decision threshold, respectively. The ANN was significantly more specific than ALT or bilirubin level or day posttransplantation at their corresponding optimum decision thresholds (P <.0001). Peak ANN output occurred 1 day earlier than peak values for either ALT or bilirubin (P <.005). The diagnostic accuracy of the ANN was greater than that of any of the individual variables that had been used as inputs. It would be a useful adjunct to conventional liver function tests for monitoring liver transplant recipients in the early postoperative period.

Acute Disease↗
PubMed2000

Cancer research studies in Native Hawaiians and Pacific Islanders.

PURPOSE: To review and assess published findings from relevant cancer research studies in Native Hawaiians and other Pacific Islanders and to develop strategies for designing and implementing successful cancer research studies in the future. METHODS: Data were collected primarily from MEDLINE and BIOSIS Preview searches of the English literature during a 30-year period for published reports of cancer surveillance studies and epidemiological and clinical cancer studies in the Native Hawaiian and Pacific Islander populations. The cancer burden was critically assessed in the retrieved citations for each of the indigenous groups from Hawai'i, American Samoa, Guam, Commonwealth of the Northern Mariana Islands, Federated States of Micronesia, Republic of Palau, and the Republic of the Marshall Islands. RESULTS: A review of the published literature revealed a lack of systematic data collection on cancer incidence and mortality in Pacific Islanders. Wide variations were found regarding the status of cancer research among ethnic groups. It is estimated that Native Hawaiians represent 0.1% of subjects accrued to cancer prevention trials, and that Pacific Islanders represent 0.5% of subjects in a large cancer screening trial. CONCLUSION: The paucity of cancer data and clinical cancer research supports the need for increased attention to these indigenous populations to improve the quality of cancer care in Native Hawaiian and Pacific Island communities.

Ethnicity↗
PubMed2000

Representation of Asian Americans in clinical cancer trials.

PURPOSE: The objectives of this study are to analyze the accrual of Asian Americans to National Cancer Institute (NCI)-supported prevention, screening/diagnosis, and treatment trials and to determine if there is proportional ethnic representation. METHODS: Data were obtained on all participants accrued to ongoing prevention and screening/ diagnosis trials and on all patients accrued to treatment trials from 1994 to mid-1998. In the analysis, the percentage of Asian Americans to the total number of trial participants is calculated. For treatment trials, participants were stratified into five age groups: 0-20 years, 21-44 years, 45-54 years, 55-64 years, and 65 or more years. RESULTS: Asian Americans represented 4.8% of subjects accrued in screening/diagnosis trials, 1.8 to 2.2% of subjects in treatment trials, and 0.9% of subjects in prevention trials. Comparison of treatment trial age groups revealed that younger Asian Americans participate significantly more in treatment trials than older Asian Americans. CONCLUSIONS: Asian American accrual in NCI-supported trials is representative of the cancer burden of Asian Americans in the United States. However, Asian Americans 65+ years are underrepresented. Their full participation in cancer trials is justified.

Adolescent↗
PubMed2000

Ecoterrorism and nontraditional military threats.

The menace facing U.S. service personnel from ecoterrorism and other nontraditional threats may increase as military deployments in war and peace increase, the availability of devastating biological, chemical, and radioactive agents increases, and adversaries or terrorist groups become more inclined to use them. A vital concern for field medical commanders is the requirement to understand the environmental issues associated with military deployment. More important is the need to recognize potential ecological threats to deployed military troops. The Gulf War was replete with numerous documented acts of ecoterrorism. The current world crisis from terrorism dictates that we be knowledgeable of the medical consequences of weapons of mass destruction and skilled in the management of casualties. The processes of human health risk assessment of deployed soldiers and ecological risk assessment are discussed as strategies to effectively prevent or reduce the health and medical consequences of ecoterrorism.

Disease↗
PubMed2000

Association of Helicobacter pylori infection with gastric cancer.

BACKGROUND: Helicobacter pylori has generated public health interest since its identification in 1983. Past studies have suggested that the bacterium plays a role in the pathogenesis of gastric cancer. More recent studies support the conclusion that the association of H. pylori with gastric cancer is causal. The purpose of this article is to review the available evidence supporting the association of H. pylori with gastric cancer. METHODS: We performed a critical review of the relevant literature published in the English language on H. pylori and gastric cancer using MEDLINE, Index Medicus for the years 1985 to 1997. The reference lists of selected articles also were reviewed to capture citations for further pertinent studies. RESULTS: H. pylori is thought to be the major cause of chronic atrophic gastritis. H. pylori gastritis is worldwide in distribution. H. pylori is now categorized by the International Agency for Cancer Research as a group 1 carcinogen, i.e., an agent that is carcinogenic to humans. Several reports from the United States have found the highest frequencies of gastric cancer in geographic areas and populations with the highest rates of acquisition of H. pylori infection. The high prevalence of H. pylori infection has been documented most notably in blacks and Hispanics, who also are at high risk for gastric cancer. CONCLUSIONS: New studies that focus on the epidemiology and pathology of H. pylori improve our understanding of its relationship with gastric cancer and advance the development of gastric cancer prevention and control strategies that are proposed.

Adult↗
PubMed1999

Mechanism of bone loss after liver transplantation: A histomorphometric analysis.

Organ transplantation is associated with increased bone loss and high fracture risk, but the pathophysiological mechanisms responsible have not been established. We have performed a histomorphometric analysis of bone remodeling before and 3 months after liver transplantation in 21 patients (14 male, 7 female) aged 38-68 years with chronic liver disease. Eight-micrometer undecalcified sections of trans-iliac biopsies were assessed using image analysis. Preoperatively, bone turnover was low with a tendency toward reduced wall width and erosion depth. The bone formation rate increased from 0.021 +/- 0.016 (mean +/- SD) to 0.067 +/- 0.055 microm2/microm/day after transplantation (p < 0.0002) and activation frequency from 0.24 +/- 0.21/year-1 to 0.81 +/- 0. 67/year-1 (p < 0.0001). No significant change was observed in wall width, but there was a trend toward an increase in indices of resorption cavity size. There was a small increase in osteoid seam width postoperatively (p< 0.02) and decrease in mineralization lag time (p < 0.001). No significant changes in indices of cancellous bone structure were observed in the postoperative biopsies. These results demonstrate a highly significant and quantitatively large increase in bone turnover in the first 3 months after liver transplantation. Although no significant disruption of cancellous bone structure was demonstrated during the time course of the study, the observed changes in bone remodeling predispose to trabecular penetration and may thus result in long-term adverse effects on bone strength.

Adult↗
PubMed1998

Prostate cancer treatment outcome in blacks and whites: a summary of the literature.

The disparate mortality rates of prostate cancer among populations have led to the question "Is therapy as effective in blacks versus whites." A review of the cancer literature that has assessed black-white outcomes supports the conclusion that equal treatment yields equal outcomes among equal patients. Although epidemiological studies demonstrate that blacks are disproportionately diagnosed with higher stage and higher grade disease, clinical studies show that equal treatment yields equal outcome regardless of race. Patterns-of-care studies demonstrate that there is not equal treatment in the United States among black and white patients.

Black or African American↗
PubMed1995

Colorectal cancer trends by race and anatomic subsites, 1975 to 1991.

OBJECTIVES: To determine whether colorectal cancer rates among black men and women show the abrupt declines seen in whites since the mid-1980s and to determine how the cancer trends vary by anatomic subsites. DATA SOURCES: Mortality data from the National Center for Health Statistics, Hyattsville, Md, and incidence and survival data from the Surveillance, Epidemiology, and End Results program of the National Cancer Institute, Bethesda, Md. MAIN OUTCOME MEASURES: Trends in incidence, survival, and mortality rates. RESULTS: For white men and women, cancer incidence rates declined for the right colon, left colon, and rectum after 1985. Stage-specific incidence rates for white men and women for each subsite had generally similar patterns. Distant-disease incidence rates declined beginning in the late 1970s, whereas regional-disease rates increased until the early to mid-1980s and then declined. An exception is the right colon in men, for which the incidence rates of distant disease did not decline, although the regional-disease pattern was similar to other sites. For blacks, colorectal cancer incidence rates changed little in the 1980s for men or women. In particular, there were no significant declines in the cancer incidence rates of the colorectum or of subsites after 1985. Black colorectal cancer mortality trends showed gender and age differences. Black men had significantly increasing colorectal cancer mortality rates from 1975 through 1992, but the increase after 1985 was observed only in men 65 years of age and older. The colorectal cancer mortality rates did not increase overall in black women in the 1980s, but the mortality rates increased slightly in women 65 years of age and older while declining in women younger than 65 years. CONCLUSIONS: For whites, the trends in colorectal cancer rates by anatomic subsite support the contention that early-detection procedures, such as sigmoidoscopy and colonoscopy, are contributing to the declines in incidence and mortality rates since 1985. The absence in blacks of significant declines in colorectal incidence or mortality rates since 1985 suggests the need for a greater emphasis on early-detection programs in the black community, particularly for elderly blacks.

Black People↗
PubMed1987

Modification of human tumor pH by elevation of blood glucose.

Nine patients with metastatic or recurrent superficial tumors of varying size and histology were administered 100 g oral glucose to investigate whether hyperglycemia can selectively lower tumor pH. pH was measured by a 21 ga modified glass needle electrode inserted through an 18 ga open-ended Angiocath. Serum glucose was monitored every 7.5 min by finger stick and a blood glucose analyzer. Tumor pH was measured over 50-80 min concomitantly with determination of blood glucose. In five nondiabetic patients (eight measurement points) tumor pH decreased 0.05-0.5 units from a pre-glucose range of 6.8-7.4 (7.14 +/- 0.08) to 6.4-7.3 (6.90 +/- 0.10) as blood glucose increased from a baseline of 80-120 mg/dl to 165-215 mg/dl. There was considerable heterogeneity from patient to patient regardless whether blood glucose increased to a peak at 40-60 min post-ingestion and then decreased, or whether it remained elevated up to the end of the 80 min observation period. In general, tumor pH decreased as blood glucose increased and then continued to fall throughout the period of observation. In one patient, tumor pH did not change although blood glucose increased to 175 mg/dl. Normal tissue pH was 7.36 +/- 0.02 when determined on four occasions in three patients (subcutaneous and intramuscular sites), and was unaffected by glucose administration. As a further control for tumor tissue and pH probe stability, pH probes in two patients were left in place for 30 min before glucose ingestion. The tumor pH was stable for the entire interval. Interestingly, three patients had an abnormal glucose response: two of those patients (one patient on two separate occasions) had an increase in blood glucose to 230-260 mg/dl in 40-60 min and pH actually increased 0.1-0.3 units. The third patient had a transient increase in blood glucose to 290 mg/dl along with a corresponding increase and subsequent decrease in tumor pH. In summary, whether glucose was given pre- or post-hyperthermia, independently of position in the tumor, and independently of whether pH increased or decreased, the slope of the curve of pH = f(time) was similar in a given patient tumor on all measurement occasions. These preliminary results suggest that hyperglycemia may be useful in non-diabetic patients, and perhaps in diabetic patients given insulin, to selectively reduce tumor pH and sensitize tumors to hyperthermia.

Administration, Oral↗
PubMed1986

United States National Cancer Institute Radiotherapy Development Program.

The United States National Cancer Institute (NCI) has long supported research in radiotherapy since its establishment by an act of Congress in 1937. One of the first grants for research awarded in 1938 was to support work in developing a cyclotron for conducting clinical research on therapeutic uses of neutrons and radioactive isotopes. Support for training cancer specialists was given high priority in the early days of NCI. In 1961, the Cancer Centers Program was instituted which included a radiation research program that became the primary source of grant support for radiotherapy clinical research centers in the US. There is a need for radiotherapy research because approximately 50-60% of people with newly diagnosed cancers will receive radiotherapy at some time during their disease. In 1979, the Radiotherapy Development Branch (RDP) assumed responsibility for all radiation program grants including radiation physics, radiobiology, and radiotherapy. The RDB manages a portfolio of grants and contracts with an annual budget of over $45 million. In fiscal year (FY) 1984, research support for individual investigator grants, program project grants, and contracts amounted to $22, 15, and 6 million, respectively. The accomplishments of NCI research grantees and contractors in radiotherapy-related areas have been considerable over the past 45 years. It is essential that NCI continue its commitment to radiotherapy research and development.

National Institutes of Health (U.S.)↗
PubMed1985

A survey of traditional medical practices used for the treatment of malignant tumors in an East African population.

A group of 119 Tanzanians with cancer were interviewed regarding previous traditional medical experiences prior to evaluation for radiation treatment. Forty-nine (49.1%) percent of the females and 40.6% of the males had been treated with traditional medicines. Seventy-four percent of the traditionally-treated patients had consulted a traditional doctor prior to being seen by a Western-trained doctor. The most common given treatment was a combination of several traditional methods. More than half of all traditionally-treated patients reported progression of their diseases after treatment. Only one patient had any subjective improvement. These patients tended to have less formal education and a lower standard of living than untreated patients. Problems associated with the diagnosis of cancer are addressed.

Adult↗
PubMed1983

Comparison of automated and rapid manual methods for the same-day identification of Enterobacteriaceae.

The Vitek AMS automated instrument method for identification of Enterobacteriaceae was compared with two rapid manual methods intended for the same purpose, the Micro ID System and the API 20E Same-Day procedure, on a series of 400 consecutive fresh clinical isolates. Results were compared with identifications obtained using the API 20E System with overnight incubation and supplemental tube biochemicals (when needed). Both the final (8-hour) and a manually requested, presumptive 5-hour result from the AMS were compared with the 4-hour results provided by the Micro ID and the 5-hour results provided by the API. The Micro ID system proved to be the most rapid and accurate of the three test systems by correctly identifying 96.8% (387/400) of isolates. The API 20E using 5-hour readings identified 90.7% (363/400) of isolates, although 96.8% (387/400) could be identified if supplemental overnight tests were employed to separate profile codes with "good likelihood, but low selectivity." The AMS correctly identified 88.8% (355/400) isolates after 5 hours, and 95.0% (380/400) following 8 hours incubation.

Automation↗
PubMed1983

Rapid identification of group D streptococci with the API 20S system.

The API 20S system (Analytab Products) was evaluated as a means of identifying 209 isolates of Lancefield group D streptococci to the species level. Results were compared with those from a conventional tube biochemical identification system and from serological grouping. Use of the latest 20S computerized data base allowed species identification of 97% (203 of 209) of test isolates after a 4-h incubation period and 99% (208 of 209) of test isolates if supplemental overnight biochemical tests were used to clarify the identity of five Streptococcus bovis-variant isolates. The API 20S system appears to be a convenient and accurate method for rapid, same-day species identification of group D streptococci.

Enterococcus faecalis↗
PubMed1983

Geographical aspects of cancer in Tanzania.

Cancer is an important cause of morbidity and mortality in Tanzania. According to the Tanzanian Cancer Registry, which records all histologically confirmed malignant tumors, the number of reported cancer cases has increased significantly over the past three decades. The most commonly diagnosed tumors are cervix cancer, skin cancer, primary liver cancer, Kaposi's sarcoma, and Burkitt's lymphoma. Geographical and tribal variations exist in disease frequency. Environmental factors appear to have a major role in the distribution. Through elimination of these factors, cancer in Tanzania could be reduced if not totally prevented.

Adolescent↗
PubMed1983

Radiotherapy in Tanzania.

The treatment of malignancies with radiotherapy and intracavitary techniques at the Tanzanian Tumor Center in Dar es Salaam, Tanzania, during an eight-month period in 1979 is reported. Cancer of the uterine cervix was the tumor most frequently treated by radiation, as well as breast, esophagus, skin, and bladder cancers.

Adolescent↗
PubMed1982

Pyridinium-2-azo-p-dimethylaniline chromophore, a new chromogenic cephalosporin for rapid beta-lactamase testing.

A new chromogenic cephalosporin, pyridinium-2-azo-p-dimethylaniline chromophore, was evaluated for use in a rapid paper strip or tube test for the detection of beta-lactamases from a variety of microorganisms. A 1-min pyridinium-2-azo-p-dimethylaniline chromophore paper strip test was found to be a convenient and accurate method for the detection of beta-lactamase-producing strains of Haemophilus influenzae and Neisseria gonorrhoeae, although it could not be relied upon to detect beta-lactamases produced by staphylococci, enteric organisms, or Bacteroides fragilis.

Bacteria↗