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Biomedical subjects

A Schwartz

Publications and source records attributed to A Schwartz.

At least 37 records · Page 2Linked to original sources
PubMed2001

The involvement of polyphenols and peroxidase activities in heavy-metal accumulation by epidermal glands of the waterlily (Nymphaeaceae).

Co-localization of polyphenols and peroxidase activity was demonstrated in epidermal glands of the waterlily (Nymphaea) by histochemistry. Total phenols, tannins and peroxidase activity were determined quantitatively in plant extracts. Polyphenols were partially identified and were found to consist mainly of hydrolyzable tannins, gallic and tannic acid derivatives. Nymphaea polyphenols were shown to chelate Cr, Hg, and Pb in vitro, and Cd-binding by polymerized polyphenols was demonstrated in leaves exposed to Cd in vivo. Both polyphenols and peroxidases were found at very high constitutive levels, which were not induced or altered by external conditions, such as light and heavy-metal stress. It is suggested that the polymerization of polyphenols by peroxidases, enhanced after heavy-metal uptake and detoxification, is responsible for the binding of heavy metals in Nymphaea epidermal glands.

Cadmium↗
PubMed2001

Phenols and phenol oxidases are involved in cadmium accumulation in the water plants Nymphoides peltata (Menyanthaceae) and Nymphaeae (Nymphaeaceae).

This comparative study investigates the mechanism of cadmium accumulation in the semiaquatic plant Nymphoides peltata (Menyanthaceae) and the aquatic plant Nymphaea (Nymphaeaceae). It was conducted as part of an ongoing study of the use of water plants for phytoremediation. Epidermal structures, known as hydropotes, are located on the abaxial epidermis of the leaf laminae of Nymphoides peltata and are shown to contain phenols, peroxidase and polyphenol oxidase activities. When plants are subjected to 50 mg/l of cadmium in the growth medium, these hydropotes accumulate cadmium. Cadmium-induced increases in phenols, peroxidase and polyphenol oxidase activities were determined in plant extracts. Cadmium binding by polymerized phenols was demonstrated in vivo. In comparison with Nymphaeae epidermal glands, N. peltata hydropotes are larger, open, and create bigger crystal, the latter principally composed of calcium and, proportionally, less cadmium. Although both plants showed similar levels of cadmium accumulation, N. peltata was sensitive while Nymphaeae was resistant to this cadmium level. It is suggested that in these water plants the main mechanism for cadmium accumulation is based on the trapping of cadmium crystals by polymerized phenols in specialized epidermal structures and this is due to peroxidase and polyphenol oxidase activities. Nymphaeae, with greater peroxidase activity and more polyphenols, is more resistant to this heavy metal than N. peltata.

Biodegradation, Environmental↗
PubMed2001

Use of transgenic mice to study voltage-dependent Ca2+ channels.

During the past decade a great number of genes encoding high- and low-voltage-dependent Ca(2+) channels and their accessory subunits have been cloned. Studies of Ca(2+) channel structure-function relationships and channel regulation using cDNA expression in heterologous expression systems have revealed intricate details of subunit interaction, regulation of channels by protein kinase A (PKA) and protein kinase C (PKC), drug binding sites, mechanisms of drug action, the ion conduction pathway and other aspects of channel function. In recent years, however, we have arrived at the brink of an entirely new strategy to study Ca(2+) channels by overexpressing or knocking out genes encoding these channels in transgenic mice. In this article, various models of gene knockout or gene overexpression will be discussed. This new approach will reveal many secrets regarding Ca(2+) channel regulation and the control of Ca(2+)-dependent cellular processes.

Animals↗
PubMed2001

Trade-offs, conflicts of interest and manipulation in Plasmodium-mosquito interactions.

A long-held view among parasitologists is that infection by malaria parasites does not harm the mosquito vector. One of the reasons for this belief is that the two partners of the association share interests in the most important life-history traits of the mosquito. Both partners benefit from increased survival and an increased rate of bloodfeeding the mosquito to increase its reproductive success and the parasite to ensure its transmission. Problems with this line of reasoning appear when one considers possible trade-offs among the mosquito's life-history parameters, which constrain the attempts by the mosquito and the parasite to maximize their success. Could these constraints differ between the two partners and thus lead to conflicts of interest and what would be the evolutionary and epidemiological consequences of conflicting interests? These questions will be investigated below.

Aedes↗
PubMed2001

Pranidipine, a 1,4-dihydropyridine calcium channel blocker that enhances nitric oxide-induced vascular relaxation.

Pranidipine, a long acting 1,4-dihydropyridine calcium channel blocker, prolongs nitric oxide (NO)-mediated relaxation of rat aorta; it prolongs acetylcholine-induced relaxation in presence of endothelium as well as nitroglycerin-induced relaxation in absence of endothelium. In rat aorta the effect of pranidipine on NO-mediated relaxation is cyclic guanosine monophosphate (cGMP)-independent, but in guinea pig carotid artery the same effect of pranidipine is cGMP-dependent. It has been reported that in co-cultured human endothelial and smooth muscle cells pranidipine, at a higher concentration (10(-6) M), enhances vasorelaxant effect of NO by blocking NO decomposition. The enhancement of NO action by pranidipine differs from the direct NO-releasing action of other 1,4-dihydropyridines. It is expected that enhancement of NO-induced vasodilatation will lead to a venodilator action in vivo and less peripheral edema. The target organ protective effects of pranidipine are also reviewed in this article.

Amlodipine↗
PubMed2001

Parathyroid cells express dihydropyridine-sensitive cation currents and L-type calcium channel subunits.

Parathyroid cells express Ca2+ -conducting currents that are activated by raising the extracellular Ca2+ concentration ([Ca2+]o). We investigated the sensitivity of these currents to dihydropyridines, the expression of voltage-dependent Ca(2+) channel (VDCC) subunits, and the effects of dihydropyridines on the intracellular free [Ca2+] ([Ca2+]i) and secretion in these cells. Dihydropyridine channel antagonists dose dependently suppressed Ca2+ -conducting currents, and agonists partially reversed the inhibitory effects of the antagonists in these cells. From a bovine parathyroid cDNA library, we isolated cDNA fragments encoding parts of an alpha(1S)- and a beta(3)-subunit of L-type Ca(2+) channels. The alpha(1S)-subunit cDNA from the parathyroid represents an alternatively spliced variant lacking exon 29 of the corresponding gene. Northern blot analysis and immunocytochemistry confirmed the presence of transcripts and proteins for alpha(1)- and beta(3)-subunits in the parathyroid gland. The addition of dihydropyridines had no significant effects on high [Ca2+]o-induced changes in [Ca2+]i and parathyroid hormone (PTH) release. Thus our studies indicate that parathyroid cells express alternatively spliced L-type Ca2+ channel subunits, which do not modulate acute intracellular Ca2+ responses or changes in PTH release.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2001

Future employment among homeless single mothers: the effects of full-time work experience and depressive symptomatology.

This study examines the relationship between work and depressive symptomatology for extremely destitute single mothers-mothers who have experienced an episode of homelessness. Using longitudinal data collected from 294 respondents who became homeless in 1992 and were followed for approximately two years, we find that a history of full-time work is the best predictor of whether a woman will find full-time employment in the aftermath of an episode of homelessness. Even an extensive history of part-time or informal work was not predictive of finding employment after leaving a homeless shelter. A woman's level of depressive symptomatology at the onset of homelessness predicted her strategy in dealing with the shelter bureaucracy. Women with full-time work histories who experienced high levels of depressive moods at the onset of a shelter episode were likely to leave the shelter quickly. Those with lower levels of depressive symptomatology stayed and were more likely than others to complete an education or job training program. Both types of women with full-time work histories were more likely than others to find full-time employment after a homeless episode. These findings suggest that policy makers must focus on providing full-time, and not part-time, work for impoverished mothers and take depressive symptomatology into account when offering assistance to homeless mothers.

Depressive Disorder↗
PubMed2001

Soluble L-selectin levels during controlled ovarian hyperstimulation.

We sought to determine whether neutrophil activation, as reflected by soluble L-selectin levels, plays a role in controlled ovarian hyperstimulation (COH) and the possible correlation between soluble L-selectin and serum sex steroid levels. The study population consisted of 14 consecutive patients undergoing our routine in vitro fertilization (IVF) long gonadotropin-releasing hormone (GnRH) analog protocol. Blood was drawn three times during the COH cycle: (1) on the day when adequate suppression was obtained (Day-S); (2) on the day of, or the day prior to, human chorionic gonadotropin (hCG) administration (Day-hCG); and (3) on the day of ovum pick-up (Day-OPU). Levels of sex steroids and plasma soluble leukocyte selectin (L-selectin) were compared among the three time points. Soluble L-selectin was measured with a commercial sandwich enzyme-linked immunosorbent assay (ELISA). The results showed significantly higher levels of soluble L-selectin on Day-OPU than on Day-S and Day-hCG, and significantly lower levels on Day-hCG than Day-S. Though no significant correlations were found between soluble L-selectin and serum estradiol or hCG levels, soluble L-selectin positively correlated with serum progesterone levels. We conclude that hCG administration leads to neutrophil activation, which correlates with the degree of luteinization. Further studies are required to elucidate the relationship between the immune system and COH. These may lead to new strategies for predicting and preventing complications of COH.

Adult↗
PubMed2001

Cancer symptom control: feasibility of a tailored, interactive computerized program for patients.

This study evaluated the feasibility of an innovative computerized symptom assessment tool, SymptomReport, and a computerized, tailored education tool, SymptomConsult, in a sample of 41 outpatients with cancer. After patients completed the computerized programs, an audiotaped telephone interview was conducted to assess patients' impressions. The study found that patients required less than 40 minutes on average to complete SymptomReport. The mean acceptability score was high 11 +/- 2. The 12 patients who completed SymptomConsult did so in an average of 20 minutes. The majority of participants indicated that the computer programs were easy, enjoyable, and informative tools. Initial formative research supports further study of these feasible computerized programs.

Adult↗
PubMed2001

Inhibition of inflammatory corneal angiogenesis by TNP-470.

PURPOSE: To determine the efficacy of the angiogenic inhibitor TNP-470 on inflammatory corneal neovascularization. Topical and systemic delivery of the drug were investigated in a murine model as well as inhibition of endothelial cell proliferation in vitro and in vivo. METHODS: The effect of TNP-470 on VEGF- and bFGF-stimulated bovine capillary endothelial (BCE) cell proliferation was evaluated in vitro. Corneal neovascularization was induced in vivo by mechanical debridement of the corneal and limbal epithelium with 0.15 M NaOH on C57BL6 mice. TNP-470 was administered systemically at 30 mg/kg body weight (BW) every other day or topically three times daily in a concentration of 5 ng/ml dissolved in methylcellulose. Vessel length was investigated on day 7. VEGF protein content in murine corneas was analyzed by ELISA on days 2, 4, and 7 of treatment. A modified bromouridine (BrdU) ELISA was used to quantify endothelial cell proliferation. RESULTS: TNP-470 exerted a dose-dependent inhibition of bFGF- and VEGF-induced endothelial cell proliferation in vitro. Both systemic and topical application of TNP-470 led to a significant reduction of inflammatory corneal neovascularization (P < 1 x 10(-5)). BrdU labeling showed that TNP-470 inhibited endothelial cell proliferation. VEGF protein levels were reduced by systemic TNP-470 treatment. CONCLUSIONS: These results suggest that TNP-470 reduces inflammatory corneal angiogenesis by directly inhibiting endothelial cell proliferation. Topical and systemic treatment with TNP-470 reduces VEGF levels that are responsible for vessel growth during the neovascularization process.

Administration, Topical↗
PubMed2001

Quantitative flow cytometry.

Flow cytometers are instruments that can quantify fluorescence intensity data and provide unique information about cell populations. Significant advances have been made in terms of calibration reagents, evaluation of the quality and limitations of the monoclonal antibodies, standardized sample preparation, and data analysis to ensure interlaboratory comparability and reproducibility. Efforts to standardize quantitative fluorescence intensity measurements impact current clinical flow cytometry applications (i.e., immunophenotyping), but also emerging technologies, such as microarray assays, which also require calibration of fluorescence intensity across different platforms.

Data Collection↗
PubMed2000

Degradation of the E7 human papillomavirus oncoprotein by the ubiquitin-proteasome system: targeting via ubiquitination of the N-terminal residue.

The E7 oncoprotein of the high risk human papillomavirus type 16 (HPV-16), which is etiologically associated with uterine cervical cancer, is a potent immortalizing and transforming agent. It probably exerts its oncogenic functions by interacting and altering the normal activity of cell cycle control proteins such as p21WAF1, p27KIP1 and pRb, transcriptional activators such as TBP and AP-1, and metabolic regulators such as M2-pyruvate kinase (M2-PK). Here we show that E7 is a short-lived protein and its degradation both in vitro and in vivo is mediated by the ubiquitin-proteasome pathway. Interestingly, ubiquitin does not attach to any of the two internal Lysine residues of E7. Substitution of these residues with Arg does not affect the ability of the protein to be conjugated and degraded; in contrast, addition of a Myc tag to the N-terminal but not to the C-terminal residue, stabilizes the protein. Also, deletion of the first 11 amino acid residues stabilizes the protein in cells. Taken together, these findings strongly suggest that, like MyoD and the Epstein Barr Virus (EBV) transforming Latent Membrane Protein 1 (LMPI), the first ubiquitin moiety is attached linearly to the free N-terminal residue of E7. Additional ubiquitin moieties are then attached to an internal Lys residue of the previously conjugated molecule. The involvement of E7 in many diverse and apparently unrelated processes requires tight regulation of its function and cellular level, which is controlled in this case by ubiquitin-mediated proteolysis.

Adenosine Triphosphate↗
PubMed2000

Architecture of Ca(2+) channel pore-lining segments revealed by covalent modification of substituted cysteines.

The cysteine accessibility method was used to explore calcium channel pore topology. Cysteine mutations were introduced into the SS1-SS2 segments of Motifs I-IV of the human cardiac L-type calcium channel, expressed in Xenopus oocytes and the current block by methanethiosulfonate compounds was measured. Our studies revealed that several consecutive mutants of motifs II and III are accessible to methanethiosulfonates, suggesting that these segments exist as random coils. Motif I cysteine mutants exhibited an intermittent sensitivity to these compounds, providing evidence for a beta-sheet secondary structure. Motif IV showed a periodic sensitivity, suggesting the presence of an alpha-helix. These studies reveal that the SS1-SS2 segment repeat in each motif have non-uniform secondary structures. Thus, the channel architecture evolves as a highly distorted 4-fold pore symmetry.

Amino Acid Motifs↗
PubMed2000

[Hemiparesis as a sequela of traumatic pseudoaneurysm of the carotid bifurcation].

HISTORY AND CLINICAL FINDINGS: A 20-year-old patient was referred to our clinic after sudden onset of a left-sided hemiparesis. His past history revealed a severe trauma 4 years ago, including multiple bone fractures, rupture of the spleen, as well as renal failure, and an acute respiratory distress syndrome, from which he showed good recovery. At that time no central-nervous symptoms could be found. However, eighteen months ago, he complained about a transient weakness of his left arm and leg. INVESTIGATIONS: Examination of the cerebral arteries by duplex-sonography showed an aneurysm on the bifurcation of the right carotid artery with a peripheral flow-reduction. This could be confirmed by CT- and MR-based angiography, which also revealed a reopened embolic occlusion of the M1-segment of the right middle cerebral artery. On CT and diffusion weighted imaging there was evidence of an ischemic infarction pattern. TREATMENT AND COURSE: Under anticoagulation therapy with heparin the patient showed complete recovery from his symptoms. Duplex-sonography as well as MR-angiography documented a complete reopening of the primarily occluded middle cerebral artery. Finally, surgical reconstruction of the aneurysmatic part of the vessel was done. CONCLUSION: This case illustrates the potential risk of a traumatic aneurysm as a potential source of ischemic brain infarctions. We emphasize the importance of imaging the cerebral arteries in traumatic patients, even in the absence of initial neurological symptom.

Adult↗
PubMed2000

Elevated levels of plasma C-reactive protein are associated with decreased graft survival in cardiac transplant recipients.

BACKGROUND: Inflammation may be involved in the origin of transplant coronary artery disease. We hypothesized that plasma levels of C-reactive protein (CRP) and interleukin-6 (IL-6), markers for systemic inflammation, would correlate with cardiac transplant graft survival. METHODS AND RESULTS: We studied 99 consecutive cardiac transplant recipients who were referred for routine endomyocardial biopsy and/or surveillance coronary angiography. Plasma levels of CRP and IL-6 were measured by their respective ELISAs. Patients were divided into 2 groups: those who died or required retransplantation and those who survived without the need for retransplantation. During the follow-up period of 5.0+/-2.7 years (range, 0.2 to 15.1 years) after transplant, 20 patients died and 9 required retransplantation. There was no significant difference in age, race, sex, cause of native myopathy, presence of diabetes, or use of aspirin, statins, or calcium channel blockers between the 2 groups. Although IL-6 did not relate to graft failure, CRP level was predictive of allograft failure (P:=0.003). The risk of allograft failure increased 36% for every 2-fold increase in CRP level. Moreover, CRP levels also correlated significantly with the frequency of grade 3 rejection (P:=0.02). In multivariate analysis, when combined with other significant predictors such as donor age and sex mismatching of the graft, CRP still significantly predicted graft failure (P:=0.025) with a 32% increase in the risk of graft failure for every 2-fold increase in CRP level. CONCLUSIONS: These findings suggest that elevated plasma levels of CRP are associated with subsequent allograft failure in cardiac transplant recipients.

Biomarkers↗
PubMed2000

The excess incidence of squamous cell esophageal cancer among us black men. Role of social class and other risk factors.

PURPOSE: To investigate the relationship between social class factors and squamous cell esophageal cancer and the extent to which alcohol, tobacco, diet, and social class contribute to the five-fold higher incidence among black than white men in the United States.METHODS: Interviews were conducted with 347 incident cases of squamous cell esophageal cancer (119 white males and 228 black males) and 1354 population-based controls (743 white males and 611 black males) from Atlanta, Detroit, and New Jersey. Risks were estimated using unconditional logistic regression controlling for potential confounders.RESULTS: Elevated risks of squamous cell esophageal cancer were associated with indicators of low social class, especially low annual income. The adjusted odds ratios (ORs) for subjects with incomes < $10,000 versus incomes of $25,000 or more were 4.3 (95% CI = 2.1-8.7) for whites and 8.0 (95% CI = 4.3-15.0) for blacks. The combination of all four major risk factors: annual income less than $25,000, moderate/heavy use of alcohol, use of tobacco for six months or longer, and consumption of less than 2.5 servings of raw fruits and vegetables per day accounted for almost all of the squamous cell esophageal cancers in whites (98%) and blacks (99%), and for 99% of the excess incidence among black men.CONCLUSIONS: Lifestyle modifications, especially a lower intake of alcoholic beverages, would markedly decrease the incidence of this cancer in both races and narrow the racial disparity in risk. Further studies into the determinants of social class may help identify a new set of exposures for this tumor that are amendable to intervention.

Journal Article↗
PubMed2000

Suppression of tumorigenicity in breast cancer cells by the microfilament protein profilin 1.

Differential display screening was used to reveal differential gene expression between the tumorigenic breast cancer cell line CAL51 and nontumorigenic microcell hybrids obtained after transfer of human chromosome 17 into CAL51. The human profilin 1 (PFN1) gene was found overexpressed in the microcell hybrid clones compared with the parental line, which displayed a low profilin 1 level. A comparison between several different tumorigenic breast cancer cell lines with nontumorigenic lines showed consistently lower profilin 1 levels in the tumor cells. Transfection of PFN1 cDNA into CAL51 cells raised the profilin 1 level, had a prominent effect on cell growth, cytoskeletal organization and spreading, and suppressed tumorigenicity of the stable, PFN1-overexpressing cell clones in nude mice. Immunohistochemical analysis revealed intermediate and low levels of profilin 1 in different human breast cancers. These results suggest profilin 1 as a suppressor of the tumorigenic phenotype of breast cancer cells.

Animals↗