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Biomedical subjects

R Vollmer

Publications and source records attributed to R Vollmer.

At least 19 recordsLinked to original sources
PubMed2004

Hydroporation as the mechanism of hydrodynamic delivery.

We have reported that a rapid tail vein injection of a large volume of plasmid DNA solution into a mouse results in high level of transgene expression in the liver. Gene transfer efficiency of this hydrodynamics-based procedure is determined by the combined effect of a large volume and high injection speed. Here, we show that the hydrodynamic injection induces a transient irregularity of heart function, a sharp increase in venous pressure, an enlargement of liver fenestrae, and enhancement of membrane permeability of the hepatocytes. At the cellular level, our results suggest that hepatic delivery by the hydrodynamic injection is accomplished by the generation of membrane pores in the hepatocytes.

Animals↗
PubMed2003

Spin-polarized electron energy loss spectroscopy of high energy, large wave vector spin waves in ultrathin fcc Co films on Cu(001).

The realm of high energy, large wave vector spin waves in ultrathin films and at surfaces is unexplored because a suitable method was not available up to now. We present experimental data for an 8 ML thick Co film deposited on Cu(001) which show that spin-polarized electron energy loss spectroscopy can be used to measure spin-wave dispersion curves of ultrathin ferromagnetic films up to the surface Brillouin zone boundary.

Journal Article↗
PubMed2003

Low-temperature specific heat of the heavy-fermion superconductor PrOs4Sb12.

We report the magnetic field dependence of the specific-heat C of single crystals of the first Pr-based heavy-fermion superconductor Pr(Os4Sb12. The variation of C at low temperature and the magnetic phase diagram inferred from C, the resistivity and magnetization provide compelling evidence of a doublet ground state. Two distinct superconducting anomalies in C indicate an unconventional superconducting state, where the splitting may arise from a weak lifting of the ground state degeneracy. In combination this identifies Pr(Os4Sb12 as a strong contender for quadrupolar pairing, i.e., superconductivity that is neither electron-phonon nor magnetically mediated.

Journal Article↗
PubMed2001

Coexistence of superconductivity and ferromagnetism in the d-band metal ZrZn2.

It has generally been believed that, within the context of the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity, the conduction electrons in a metal cannot be both ferromagnetically ordered and superconducting. Even when the superconductivity has been interpreted as arising from magnetic mediation of the paired electrons, it was thought that the superconducting state occurs in the paramagnetic phase. Here we report the observation of superconductivity in the ferromagnetically ordered phase of the d-electron compound ZrZn2. The specific heat anomaly associated with the superconducting transition in this material appears to be absent, and the superconducting state is very sensitive to defects, occurring only in very pure samples. Under hydrostatic pressure superconductivity and ferromagnetism disappear at the same pressure, so the ferromagnetic state appears to be a prerequisite for superconductivity. When combined with the recent observation of superconductivity in UGe2 (ref. 4), our results suggest that metallic ferromagnets may universally become superconducting when the magnetization is small.

Journal Article↗
PubMed2000

Context effects and the (mal)adaptive nature of guilt and shame in children.

Symptoms of internalization were examined in relation to children's self-reports of three emotions in situations that were either ambiguous or unambiguous as to the child's responsibility for various standard violations. Children ranging in age from 6 to 13 years were drawn from elementary schools (61 boys, 79 girls, mean age = 8.7) and from a community mental health center (23 boys, 18 girls, mean age = 8.5) to which they had been referred for problems related to internalization or externalization. Shame proneness was consistently linked to internalizing symptoms across contexts. Guilt proneness, in response to ambiguous scenarios, was also associated with internalization, whereas pride responses were unrelated to symptoms. Few age- or gender-related differences were found. The results cast doubt on notions that self-conscious emotions, such as guilt, are necessarily adaptive or maladaptive. Systematic research is needed to understand which features of any emotion contribute to children's psychological adjustment.

Adaptation, Psychological↗
PubMed1998

Tumor lysis syndrome and acute renal failure after treatment of non-small-cell lung carcinoma with combination irinotecan and cisplatin.

Tumor lysis syndrome, characterized by multiple metabolic abnormalities resulting from abrupt tumor cell death and release of intracellular constituents and metabolites, is most commonly associated with the treatment of highly chemotherapy-sensitive lymphoid and leukemic neoplasms. The authors report a case of tumor lysis syndrome accompanied by acute renal failure that occurred in a patient with stage IV non-small-cell lung cancer who was treated with topoisomerase I inhibitor, irinotecan, and cisplatin. Consistent with the rapid tumor lysis, an objective, marked, early clinical response was observed. Attention to adequate hydration, electrolytes, and renal function should be given to outpatients with non-small-cell lung cancer who receive newer chemotherapeutic agents that have greater efficacy toward this group of tumors.

Acute Kidney Injury↗
PubMed1994

Homozygous deletion on chromosome 9p and loss of heterozygosity on 9q, 6p, and 6q in primary human small cell lung cancer.

We analyzed the pattern of allelic loss in 33 primary human small cell lung cancers (SCLCs) using highly informative microsatellite markers on chromosomes 2p, 3p, 5q, 6, 9, 13q, and 17p. Nineteen of these tumors (58%) displayed loss of heterozygosity on chromosome 9. Fourteen SCLCs demonstrated loss of heterozygosity for all informative markers on both chromosomal arms; two tumors demonstrated partial loss on chromosome 9p. In one tumor, a multiplex polymerase chain reaction assay disclosed a homozygous deletion at 9p21-22 including the markers IFN-alpha, D9S126, and D9S171. Two SCLCs retained all informative markers on 9p but showed allelic loss of the entire 9q arm, while one case had a partial loss of proximal 9q extending into all of 9p. Analysis of other chromosomal arms showed loss of heterozygosity on 3p (93%), 5q (75%), 6p (46%), 6q (47%), 13q (75%), and 17p (93%). It was necessary to test multiple markers at several loci because of the frequent expression of microsatellite instability that confounded our mapping efforts in SCLCs with replication errors. This study demonstrates the frequent loss of a suppressor gene locus on chromosome 9p21-22 and identifies novel suppressor loci on 6p, 6q, and 9q in primary SCLC.

Adult↗
PubMed1994

Frequent microsatellite instability in primary small cell lung cancer.

Alterations in microsatellite sequences characterize hereditary nonpolyposis colorectal cancer. This microsatellite instability is due in some kindreds to a germline mutation of the mismatch repair gene hMSH2 on chromosome 2p. Although microsatellite alterations have been reported in other hereditary nonpolyposis colorectal cancer-associated tumors including endometrial and gastric cancers, such changes were not detected in most other major neoplasms. We found that 15 of 33 (45%) primary small cell lung cancers, tumors not found in the hereditary nonpolyposis colorectal cancer syndrome, displayed alterations of microsatellite loci which consisted of deletions or expansions of (CA)n dinucleotide repeats. In 8 of these 15 neoplasms, microsatellite instability was detected in more than 10% of all tested alleles. However, small cell lung cancers that revealed instability contained widespread allelic loss and had a uniformly poor prognosis. These results expand considerably the known spectrum of tumors with microsatellite instability.

Adult↗
PubMed1990

Loss of heterozygosity for genes on 11p and the clinical course of patients with lung carcinoma.

Forty-five primary human lung carcinomas were evaluated for the loss of heterozygosity for genes on the short end of chromosome 11. Of 40 evaluable heterozygous cases, loss of the 11p genes c-H-ras and insulin was documented in nine cases (22%). The clinical parameters investigated for each patient included the disease stage at presentation, the presence of metastatic disease in either bronchial or mediastinal lymph nodes, and the presence of positive parietal pleural margins in the surgically resected specimen. There were no differences found with respect to these indicators when patients exhibiting the loss of heterozygosity were compared with those who did not have such genetic loss. In addition, when the clinical courses of the two patient groups were compared, there was no difference in survival. We conclude that the loss of heterozygosity for c-H-ras and insulin on 11p is a common finding in primary non-small cell human lung carcinomas but does not confer a more aggressive phenotype on these tumors. Although this genetic lesion may be important in the initial transformation of the cells to carcinoma, the available data for lung carcinoma are insufficient to prove causality.

Alleles↗
PubMed1990

Acral melanoma: a review of 185 patients with identification of prognostic variables.

One hundred eight-five patients with acral melanoma treated since 1972 were reviewed. These included 53 subungual lesions, 123 plantar lesions, and 9 palmar lesions. Eighty percent presented with stage I disease. Mean age was 57 years. Males outnumbered females 1.1:1. Seventeen percent (17%) were blacks. Actuarial 10-year survival was 58% for stage I patients and 35% for stage II patients. Univariate Cox regression analyses identified 5 prognostic variables affecting survival: stage at diagnosis (P less than 0.001), race (P less than 0.001), ulceration (P = 0.012), Clark's level (P = 0.014), and thickness of the primary lesion (P = 0.013). Factors unrelated to survival included sex of the patient, site (volar vs. subungual), histology, and treatment with amputation. Multivariate analysis for patients with stage I lesions identified race (P = 0.001) and ulceration (P = 0.018) as significant variables, with thickness approaching significance (P = 0.094). In an additional series of 71 patients with melanomas arising from extremity sites near the junction of glabrous and non-glabrous skin, survival was significantly poorer for those arising from glabrous skin (P = 0.024), and reflects a higher incidence of metastatic disease at diagnosis. Specific active immunotherapy was the principal adjuvant used for these patients, and survival was comparable to that reported with regional perfusion therapy. Acral melanoma a) has a strong racial predilection, b) carries a grave prognosis, and c) arises from glabrous skin. It is a clinical entity distinct from other extremity melanomas. Surgical management with either wide excision or amputation is appropriate for the primary lesion.

Adolescent↗