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Biomedical subjects

D Zhang

Publications and source records attributed to D Zhang.

At least 703 records · Page 39Linked to original sources
PubMedDate not supplied

Factors influencing unawareness of hypertension among older Mexican Americans.

BACKGROUND: The objective of the study was to identify factors associated with unawareness of hypertension among Mexican Americans age 65 years and older. METHODS: This was a population-based survey of 3,050 older Mexican Americans conducted in five Southwestern states in 1993-1994. An in-home interview included sociodemographics, review of medications, and blood pressure measurements. RESULTS: Sixty percent of all subjects were hypertensive, and 37% of these were unaware of their diagnosis. Unaware hypertensive had significantly higher mean blood pressures than did aware hypertensives (145.7/ 86.2 mm Hg vs 142.4/83.1 mm Hg). While 77% of aware hypertensives were treated, only 10% of unaware hypertensives were treated. In multivariate analyses, factors associated with unawareness included male gender (OR = 1.8), being married (OR = 1.6), having Medicaid (OR = 1.6), having made fewer than two visits to a doctor in the past year (OR = 2.8), having a history of heart disease (OR = 0.57) or stroke (OR = 0.37), and having poor self-reported health (OR = 0.43). CONCLUSION: Despite 3 decades of hypertension detection and education programs, unawareness of hypertension remains high among older Mexican Americans. There is a continued need for community-based education programs for hypertensives who are unaware of their diagnosis, and also there is need for programs to increase access to primary care physicians.

Aged↗
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Electrical signal transmission and gap junction regulation in a bone cell network: a cable model for an osteon.

A cable model is formulated to estimate the spatial distribution of intracellular electric potential and current, from the cement line to the lumen of an osteon, as the frequency of the loading and the conductance of the gap junction are altered. The model predicts that the characteristic diffusion time for the spread of current along the membrane of the osteocytic processes, 0.03 sec, is nearly the same as the predicted pore pressure relaxation time in Zeng et al. (Annals of Biomedical Engineering. 1994) for the draining of the bone fluid into the osteonal canal. This approximate equality of characteristic times causes the cable to behave as a high-pass, low-pass filter cascade with a maximum in the spectral response for the intracellular potential at approximately 30 Hz. This behavior could be related to the experiments of Rubin and McLeod (Osteoporosis, Academic Press, 1996) which show that live bone appears to be selectively responsive to mechanical loading in a specific frequency range (15-30 Hz) for several species.

Action Potentials↗
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A new human prostate carcinoma cell line, 22Rv1.

A cell line has been derived from a human prostatic carcinoma xenograft, CWR22R. This represents one of very few available cell lines representative of this disease. The cell line is derived from a xenograft that was serially propagated in mice after castration-induced regression and relapse of the parental, androgen-dependent CWR22 xenograft. Flow cytometric and cytogenetic analysis showed that this cell line represents one hyper DNA-diploid stem line with two clonal, evolved cytogenetic sublines. The basic karyotype is close to that of the grandparent xenograft, CWR22, and is relatively simple with 50 chromosomes. In nude mice, the line forms tumors with morphology similar to that of the xenografts, and like the parental CWR22 and CWR22R xenografts, this cell line expresses prostate specific antigen. Growth is weakly stimulated by dihydroxytestosterone and lysates are immunoreactive with androgen receptor antibody by Western blot analysis. Growth is stimulated by epidermal growth factor but is not inhibited by transforming growth factor-beta1.

Animals↗
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Ocular fundus lesions in systemic lupus erythematosus model mice.

We investigated the ocular fundus of (NZWXBXSB) F1 mice, which are considered to be a good model for systemic lupus erythematosus (SLE) with antiphospholipid syndrome. The abnormal fundus findings were documented by fundus photography, and the chorioretinal lesions were studied histopathologically. The incidence of ocular fundus abnormalities and systemic signs in these F1 mice was significantly higher in males than in females, as with the systemic symptoms. This indicated an influence of the Yaa (Y chromosome-linked autoimmune acceleration) gene. Lesions in the fundus appeared as white spots, which increased in number during the course of the disease and developed into retinal detachment in some animals. This developmental course resembled the course of patients with multifocal posterior pigment epitheliopathy. Dilatation of the veins and narrowing of arteries were marked. Histopathological findings included: (1) destruction of the photoreceptor cell layer, (2) degeneration and loss of the retinal pigment epithelium, (3) thickening of the wall of the choroidal arterioles, and (4) narrowing and occlusion of the choriocapillaris associated with hyaline degeneration and thrombus formation. The study of the SLE mouse model should contribute to the understanding of the abnormalities in the fundus associated with collagen diseases.

Animals↗
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Perinatal manganese exposure: behavioral, neurochemical, and histopathological effects in the rat.

Manganese chloride (Mn) was dissolved in the drinking water (0, 2, or 10 mg/ml) of dams and their litters from conception until postnatal day (PND) 30. Parturition was uneventful in the Mn-exposed rats and no physical abnormalities were observed. The rats exposed to 10 mg/ml Mn showed a 2.5-fold increase in cortical Mn levels. Their weight gain was attenuated from PND 9-24 and they were hyperactive at PND 17. Neither the 2 nor the 10 mg/ml Mn-exposed groups differed from the controls on the elevated plus apparatus or on the Morris water maze and the radial arm maze. Brain monoamine levels and choline acetyltransferase activity were affected. Tyrosine hydroxylase immunohistochemistry showed that dopamine cells of the substantia nigra were intact. Glial fibrillary acidic protein immunoreactivity was not increased in cortex, caudate, and hippocampus. However, both the low- and high-dose Mn-exposed groups showing thinning of the cerebral cortex. This could have resulted from perinatal malnutrition or from a direct effect of Mn on cortical development.

Analysis of Variance↗
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Cost considerations as potential barriers to cancer treatment.

PURPOSE: An analytical cross-sectional survey was conducted to determine the prevalence of barriers to cancer treatment in Texas as perceived by diagnosed cancer patients. Results reported here address the role of insurance coverage, indirect costs (transportation, lodging, and work days lost), and direct costs of care as barriers to treatment for white, black, and Hispanic cancer patients. Specific objectives of the analyses undertaken here are to examine 1) racial/ethnic differences in insurance coverage; 2) barriers relating to insurance coverage experienced by cancer patients; and 3) role of treatment-related costs as barriers to cancer treatment. DESCRIPTION OF STUDY: A mail questionnaire was developed to assess the perceived barriers to cancer treatment in Texas for adult cancer patients, 17 years and older, who had been diagnosed with breast, colon, cervical, prostate, or lymphoma during the period of 1989 to 1993. The sampling frame for this study was obtained from a network of cancer treatment facilities throughout the state of Texas within the University of Texas M.D. Anderson Cancer Center Texas Community Oncology Network. A total of 593 cancer patients returned their surveys, yielding a 65.2% response rate. Weighting adjustments were then made to correct for differential sampling and response rates by racial groupings and type of cancer. All of the analyses used adjusted weights. RESULTS: The findings document the financial considerations (insurance, direct and indirect costs) as they relate to barriers to cancer treatment. Specific insurance premium-related barriers with regard to maintaining and affording coverage were more prevalent for blacks. Hispanics were less likely to have insurance coverage; however, more blacks reported being denied insurance coverage when they changed jobs compared with whites and Hispanics. Minorities, particularly Hispanics, were more likely to have experienced cost-related barriers associated with medications, diagnostic tests, and hospitalizations. In addition, Hispanics experienced significant out-of-pocket costs in paying for cancer treatment. CLINICAL IMPLICATIONS: This research shows the need for staff at cancer treatment facilities to be aware that there are nonclinical, financial factors that are important considerations in the treatment of cancer patients. Assessment of cancer patients during the diagnostic and treatment stages, possibly through case management, will provide information on potential barriers to treatment for individual patients. Hospital programs that reimburse out-of-pocket costs, transportation costs to obtain services, and lodging accommodations may be available. Additional services may be offered through cancer advocacy groups, such as the American Cancer Society and the National Coalition for Cancer Survivors, to assist patients with managing costs and overcoming barriers to care.

Adolescent↗
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The role of the IGF-I receptor in the regulation of matrix metalloproteinases, tumor invasion and metastasis.

The breakdown of the extracellular matrix (ECM) by proteinases is an essential step in the process of cancer invasion and metastasis. Malignant progression is frequently associated with upregulated production and/or activity of one or several ECM degrading proteinases. Prominent among them are the matrix metalloproteinases (MMPs). The MMPs constitute a family of structurally related, zinc-dependent endopeptidases collectively capable of degrading essentially all the components of the extracellular matrix. At present, 23 members of the human MMP gene family are known. The increased expression and/or activity of one or more members of this family have been documented in essentially all human malignancies and some have been implicated in the process of angiogenesis. Prominent among those are MMP-2 and MT1-MMP, two metalloproteinases that form a cell membrane-associated complex leading to MMP-2 activation and ECM proteolysis. Here, we review our data that identified the type 1 insulin-like growth factor receptor (IGF-IR) as a regulator of tumor invasion and the synthesis of MT1-MMP and MMP-2 and report on the signal transduction pathways that mediate this regulation. These findings are discussed in the context of a broader review of the role of the IGF-IR/IGF axis in the regulation of tumor invasion and metastasis.

Animals↗
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Measuring frailty in the hospitalized elderly: concept of functional homeostasis.

Functional homeostasis is the ability of an individual to withstand illness without loss of function. We investigate whether the level of functional homeostasis predicts adverse outcomes in the 6 months posthospital discharge in older men and women. A prospective cohort study was conducted in an acute care geriatric inpatient unit of a university hospital. Subjects included a consecutive series of patients admitted to the unit. The Functional Independence Measure (FIM) instrument was used to assess patients at four time points: preillness, hospital admission, hospital discharge, and 6 months postdischarge. Of the 122 subjects available for analysis, 64 (52%) experienced a decline in functional level from preillness to hospital discharge and were defined as having poor functional homeostasis, whereas 58 (48%) experienced no change or an increase in functional status and were defined as having good functional homeostasis. Those with poor functional homeostasis had a higher 6-month readmission rate to the hospital (59.4 v 39.7%; P=0.03) and a higher rate of any adverse outcome (78.1 v 50%; P=0.001) than those with good functional homeostasis. In logistic regressive analyses, functional homeostasis remained a significant and powerful predictor of adverse outcomes independent of actual level of function at discharge, age, gender, living status, and other factors that might influence outcomes. Change in functional status associated with an acute illness is an independent predictor of adverse outcomes and, in this study, a better predictor than actual level of function at discharge. Functional homeostasis is one approach to the quantification of the important but elusive concept of frailty in the elderly.

Activities of Daily Living↗
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Moderate sodium restriction enhances the pressor response to hyperlipidemia in obese, hypertensive patients.

The effect of dietary sodium restriction on insulin, lipids, and blood pressure has been controversial. Evidence suggests that adverse short-term effects in response to very low-salt diets do not persist long-term with modest sodium restriction. In this study, the effects of modest dietary sodium restriction (60 and 120 mmol sodium) were measured for 3 weeks in 12 lean normotensives and 10 obese hypertensives. Blood pressure, plasma lipids, and the pressor response to an infusion of Intralipid and heparin were obtained. In contrast to previous reports concerning very low-salt diets, obese hypertensives did not manifest a pressor response or an adverse lipid effect with moderate salt restriction. Obese hypertensives were not more salt-sensitive than lean normotensives and did not manifest a different hemodynamic response to 4-hour infusion of Intralipid and heparin while on the 120-mmol/day salt diet. During the 60-mmol/day salt diet, however, plasma triglycerides increased more in obese than in lean volunteers during the Intralipid and heparin infusion (398+/-38 vs. 264+/-18 mg/dL; p<0.05), and there were greater increases in mean blood pressure (12+/-2 vs. 7+/-2 mm Hg; p<0.05) and systemic vascular resistance (111+/-38 vs. 225+/-44 dyne.sec.cm-5) as well as a larger decrease in small artery compliance (22.5+/-0.6 vs. 20.4+/-0.6 mL/mm Hg x 100; p<0.05). These data suggest that modest dietary sodium restriction in obese hypertensives does not adversely affect baseline blood pressure or lipids, but it does magnify their adverse lipid and hemodynamic response to fat loading.

Adult↗
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Electrical signal transmission in a bone cell network: the influence of a discrete gap junction.

A refined electrical cable model is formulated to investigate the role of a discrete gap junction in the intracellular transmission of electrical signals in an electrically coupled system of osteocytes and osteoblasts in an osteon. The model also examines the influence of the ratio q between the membrane's electrical time constant and the characteristic time of pore fluid pressure, the circular, cylindrical geometry of the osteon, and key simplifying assumptions in our earlier continuous cable model (see Zhang, D., S. C. Cowin, and S. Weinbaum. Electrical signal transmission and gap junction regulation in a bone cell network: A cable model for an osteon. Ann. Biomed. Eng. 25:379-396, 1997). Using this refined model, it is shown that (1) the intracellular potential amplitude at the osteoblastic end of the osteonal cable retains the character of a combination of a low-pass and a high-pass filter as the corner frequency varies in the physiological range; (2) the presence of a discrete gap junction near a resting osteoblast can lead to significant modulation of the intracellular potential and current in the osteoblast for measured values of the gap junction coupling strength; and (3) the circular, cylindrical geometry of the osteon is well simulated by the beam analogy used in Zhang et al.

Animals↗
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Diclofenac sodium attenuates neural activity after photorefractive keratectomy in rabbits.

BACKGROUND: Photorefractive keratectomy for treating myopia has been associated with severe postoperative pain. The purpose of the present study was to investigate, in a rabbit model, the early effects of laser ablation on the physiology of the sensory nerves of the cornea. METHODS: Neurophysiologic monitoring of the corneal nerves was carried out 4 to 6 hours after 5-mm diameter, circular PRK ablations with a central depth of 85 microns. The effect of topical 0.1%, 0.25%, and 0.5% diclofenac sodium on the physiologic response to chemical and mechanical stimulation was evaluated. Corneas were prepared for anatomic studies of corneal innervation. RESULTS: Heightened neural activity was observed in the corneal nerves after ablation, and exaggerated responses to sensory stimulation with hypertonic sodium chloride solutions were recorded. Diclofenac sodium at 0.1% decreased the response to 0.5 M NaCl and 0.7 M NaCl to 67 +/- 9% and 68 +/- 7% (mean +/- standard error) of the control response. Mechanically sensitive nerves were more resistant to diclofenac; 0.1% diclofenac had no effect, but 0.25% diclofenac reduced the response significantly (P < 0.05). Anatomic observations showed that the ablation extended through the neural plexus. By 72 hours, long neurites tipped with growth cones had advanced into the injured region, indicating the initiation of neural regeneration. CONCLUSIONS: Diclofenac sodium was effective in attenuating neural activity in the cornea after excimer laser ablation. The action of this agent was shown to be different from that of a topical anesthetic, which rapidly and totally inhibited the response to all forms of stimulation.

Animals↗
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Cryopreservation of apple dormant buds and shoot tips.

Shoot tips excised from apple (Malus domestica Borkh. cv. Golden Delicious) dormant buds immediately before freezing were successfully cryopreserved using three different methods (vitrification, encapsulation-dehydration and two-step freezing). Two-step freezing produced the highest in vitro growth recovery (83%) of cryopreserved shoot tips, followed by vitrification (60%) and encapsulation-dehydration (33%). By contrast, when dormant buds were cryopreserved using the two-step freezing technique, shoot tips excised from buds after rewarming and cultured in vitro displayed only 16% recovery.

Cryopreservation↗
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Single jejunoileal and right colonic carcinoids as midgut tumors. A study collating immunophenotypes and histogenesis.

The jejunoileum and the right colon, both of which are located in the midgut, have some histologic similarities such as the presence of Paneth cells and intraepithelial endocrine cells (IEECs). Since gastrointestinal (GI) carcinoids arise from the same stem cells as GI endocrine cells, the question was whether or not there might also be similarities in the histogenesis of jejunoileal carcinoids (JICs) and right colonic carcinoids (RCCs). Ten single JICs and 3 RCCs together with their respective controls were stained using various neurohormonal immunoreagents. Our results showed that neither the JICs nor the RCCs appeared to arise from a background of diffuse IEEC hyperplasia. Furthermore, in the jejunoileum, serotonergic progenitor cells appear to have a proclivity for neoplastic transformation, as do cells of the pancreatic polypeptide and glucagon lineage in the right colon.

Carcinoid Tumor↗
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The role of informal and formal social support networks for patients with cancer.

PURPOSE: In this study, the authors examined the role of informal and formal social support networks in mitigating barriers to cancer treatment among whites, blacks, and Hispanics, based on a representative sample of cancer patients in Texas. DESCRIPTION OF STUDY: The sample frame for this study was obtained from the University of Texas M. D. Anderson Cancer Center's Texas Community Oncology Network, a consortium of cancer treatment facilities in Texas. Of the 910 patients who were contacted, 593 (65%) responded to the survey. RESULTS: The results show the value of social support networks in assisting cancer patients with continuing treatment. An important finding indicated that health professionals do not provide information regarding social support groups to patients with cancer at the time of diagnosis. Fewer than half of the respondents were asked whether they would be interested in joining a formal social support group. Individuals of all racial/ethnic groups reported that the formal support groups provided emotional assistance. Minorities were more apt to report that the formal support groups helped with continuing treatment. In addition, informal social support networks, such as extended families and civic clubs, were seen as more helpful for blacks and Hispanics as compared with whites. CLINICAL IMPLICATIONS: The need for formal and informal networks is indicated by the results of this study, which show that networks, such as relationships with family, friends, and relatives, play an important role in assisting patients in coping with their cancer. These networks are part of the patient's total treatment experience and must be acknowledged by healthcare professionals. A large number of patients are not asked to join social support groups, suggesting a need for training healthcare professionals to provide information regarding the potential benefits of support groups for cancer patients.

Adolescent↗
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Transportation as a barrier to cancer treatment.

PURPOSE: Patients with cancer must overcome many psychological, social, and economic barriers to obtain needed treatment. Because of the need for repeated visits for cancer treatment on either an outpatient or an inpatient basis, one of the major issues that patients with cancer must confront is that of arranging for transportation to care. METHODS: This study compares the distance and mode of transportation to radiotherapy and chemotherapy and perceptions of transportation as a barrier to care among white, black, and Hispanic cancer patients receiving treatment from a consortium of cancer treatment facilities in Texas. A mail questionnaire was developed to assess the perceived barriers to cancer treatment for patients who had been diagnosed clinically with breast, colon, cervical, or prostate cancer, or lymphoma between 1989 and 1993. A total of 910 surveys were mailed to prospective participants. Of the surveys mailed, 593 were returned, yielding a 65.2% response rate. By race, the respondents included whites (42%), blacks (40%), Hispanics (15%), and Asian-Pacific Islanders (3%). Two respondents were 17 years of age; the remaining respondents were 18 years or older. RESULTS: This study shows that some patients may forgo needed treatment because of problems with transportation. This was perceived as an issue more for minority patients than for white patients. Black and Hispanic patients consistently reported that barriers such as distance, access to an automobile, and availability of someone to drive them to the treatment center were potential major problems. The distance to the facilities was farther for whites than for blacks and Hispanics. Patients generally had to travel farther for chemotherapy than for radiotherapy. CLINICAL IMPLICATIONS: Patients, particularly minorities, may opt to forgo needed care in the absence of available and affordable means of transportation to treatment facilities. These findings demonstrate the need for healthcare providers to be aware of the transportation problems that patients with cancer experience in obtaining treatment. Healthcare providers must work with patients, their families, and volunteer agencies in the community to facilitate transportation to cancer treatment services.

Adolescent↗