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Biomedical subjects

R E Lee

Publications and source records attributed to R E Lee.

At least 55 records · Page 3Linked to original sources
PubMed1998

Osmotic and freezing tolerance in spermatozoa of freeze-tolerant and -intolerant frogs.

The wood frog (Rana sylvatica) is a freeze-tolerant species that encounters subzero temperatures during its winter breeding season, whereas the leopard frog (R. pipiens) is freeze intolerant and breeds in spring. Osmotic and freezing tolerances of spermatozoa from these species were inferred from spermolysis rate, integrity of the plasma membrane as judged using vital dye assay, and motility rate. Sperm of R. sylvatica became motile in hypotonic media (</=220 mosmol/kg) and tolerated in vitro exposure to osmotic concentrations spanning nearly three orders of magnitude. Relative to sperm from R. sylvatica, which were unaffected by freezing at temperatures of -4 degrees C or greater, R. pipiens sperm were more susceptible to osmotic damage and cryoinjury. These differences likely reflect cellular adaptations to somatic freezing in R. sylvatica. Unprotected sperm from both species were extensively damaged by freezing at -8 degrees C, but the presence of glucose, the cryoprotectant used by R. sylvatica, or the permeant glycerol markedly diminished cryoinjury. These data suggest the feasibility of developing gamete cryopreservation protocols to aid efforts in conserving amphibian populations.

Animals↗
PubMed1998

Soil hydric characteristics and environmental ice nuclei influence supercooling capacity of hatchling painted turtles Chrysemys picta.

Hatchling painted turtles (Chrysemys picta) hibernate in their shallow natal nests where temperatures occasionally fall below -10 C during cold winters. Because the thermal limit of freeze tolerance in this species is approximately -4 C, hatchlings rely on supercooling to survive exposure to extreme cold. We investigated the influence of environmental ice nuclei on susceptibility to inoculative freezing in hatchling C. picta indigenous to the Sandhills of west-central Nebraska. In the absence of external ice nuclei, hatchlings cooled to -14.6 1.9 C (mean s.e.m.; N=5) before spontaneously freezing. Supercooling capacity varied markedly among turtles cooled in physical contact with sandy soil collected from nesting locales or samples of the native soil to which water-binding agents (clay or peat) had been added, despite the fact that all substrata contained the same amount of moisture (7.5 % moisture, w/w). The temperature of crystallization (Tc) of turtles exposed to frozen native soil was -1.6 0.4 C (N=5), whereas turtles exposed to frozen soil/clay and soil/peat mixtures supercooled extensively (mean Tc values approximately -13 C). Hatchlings cooled in contact with drier (less than or equal to 4 % moisture) native soil also supercooled extensively. Thus, inoculative freezing is promoted by exposure to sandy soils containing abundant moisture and little clay or organic matter. Soil collected at turtle nesting locales in mid and late winter contained variable amounts of moisture (4-15 % w/w) and organic matter (1-3 % w/w). In addition to ice, the soil at turtle nesting locales may harbor inorganic and organic ice nuclei that may also seed the freezing of hatchlings. Bulk samples of native soil, which were autoclaved to destroy any organic nuclei, nucleated aqueous solutions at approximately -7 C (Tc range -6.1 to -8.2 C). Non-autoclaved samples contained water-extractable, presumably organic, ice nuclei (Tc range -4.4 to -5.3 C). Ice nuclei of both classes varied in potency among turtle nesting locales. Interaction with ice nuclei in the winter microenvironment determines whether hatchling C. picta remain supercooled or freeze and may ultimately account for differential mortality in nests at a given locale and for variation in winter survival rates among populations.

Animals↗
PubMed1998

A home-based behavioral intervention to promote walking in sedentary ethnic minority women: project WALK.

A home-based telephone and mail intervention was evaluated for its effectiveness in promoting walking in a sample of sedentary, ethnic minority women. One hundred twenty-five women (ages 23-54) were randomly assigned to behavioral or brief educational interventions. Women in the 8-week behavioral condition received behavior change materials through the mail and 6 structured telephone counseling sessions. Educational condition participants received a single 5-min telephone call and educational information. Both groups reported significantly increased walking at a 2-month posttest (M change = 86 and 81 min per week for behavioral and educational groups, respectively) and 5-month follow-up (M change = 40 and 52 min per week). A 30-month follow-up of 50 participants indicated both groups continued to report more walking than at baseline. The behavioral intervention was not superior to the educational condition at any assessment point. The findings may be explained as (a) both interventions were equally effective, so extensive telephone counseling is unnecessary; (b) changes over time reflected secular trends; or (c) increases in self-reported walking may be due to socially desirable reporting. Other strategies need to be evaluated for promoting walking that are tailored to the needs of ethnic minority women.

Adult↗
PubMed1997

Screening of newborn babies for familial ureteric reflux.

BACKGROUND: Vesicoureteric reflux (VUR) is not usually diagnosed until it is complicated by urinary infection. Prevention probably requires diagnosis in a newborn baby before urinary infection occurs because the peak incidence for infection is in early infancy. VUR is a familial disorder. We sought to find out whether an at-risk group of newborn babies could be identified on the basis of the parents' family history. METHODS: Over a 3-year period, pregnant women attending the antenatal clinics of three hospitals in the northeast of England were screened for evidence of urinary-tract disease in themselves or their families with a view to eliciting a history of VUR. When a woman, her partner, or a member of either family had a definite (by cystography records) or probable positive history, we recruited the mother to our study. Renal ultrasonography and cystography were done on the newborn babies soon after delivery, and a dimercaptosuccinic acid (DMSA) radioisotope scan at 3 months was done on those with VUR. FINDINGS: The estimated number of deliveries during the study period was 34,555; 20,891 women were screened; and 211 were recruited and delivered. The index cases were identified from a wide range of family relationships, though over half consisted of mothers and siblings, 19 babies had more than one index case and in 21 families there was one index for more than one baby or a link between families. Cystography was carried out on 186 newborn babies; 38 (20.4%) had VUR. The proportion of newborn babies with VUR among linked index families was 31%. Mothers and siblings amounted to 71% of the index cases for newborn babies with VUR. The difference between confirmed and assumed index cases in VUR prediction was not significant. The female/male sex ratio among index cases was more than 4, but among newborn babies with VUR it was 1.5. Renal ultrasound showed no correlation with VUR, and all DMSA scans but one were normal. No newborn baby developed complications resulting from cystography. INTERPRETATION: The screening of pregnant women for familial VUR is worthwhile because the frequency of VUR among the newborn babies of those with such a history is significantly higher than in the general population (frequency of VUR 1-2%), particularly if the family history involves more than one member, or more than one generation.

Female↗
PubMed1997

Mycolic acid biosynthesis: definition and targeting of the Claisen condensation step.

Through the use of 2,2-[2H]palmitic acid pulse labeling of the whole cells of C. matruchotti and analysis by gas chromatography-mass spectrometry of the non-labeled and [2H]-labeled corynomycolates, we established a new mechanism for palmitate condensation devoid of the postulated carboxylation step. This evidence allowed the design and synthesis of several structurally related antagonists against the condensation reactions which were shown to possess potent in vivo activity against C. matruchotti with complete inhibition of growth on solid media at concentrations between 1-10 microg/ml. In addition, a cell-free in vitro assay of corynomycolate synthesis was developed to allow the screening of these and other antagonists.

Anti-Bacterial Agents↗
PubMed1997

Characterization of the in vitro synthesized arabinan of mycobacterial cell walls.

Previous studies have shown that polymerized [14C]arabinan can be synthesized from polyprenylphosphate-[14C]arabinose by the particulate enzymes of Mycobacterium smegmatis [R.E. Lee, K. Mikusová, P.J. Brennan and G.S Besra (1995) J. Am. Chem. Soc. 117, 11829-11832]. In the present investigation, the [14C]arabinan product was biochemically characterized. Sizing chromatography revealed a molecular weight consistent with that expected from mature arabinan. Digestion of the [14C]arabinan with a mixture of arabinases produced oligo[14C]arabinoside fragments including hexa[14C]arabinoside and tetra[14C]arabinoside which originated from the non-reducing terminal regions of the polymer, and di[14C]arabinoside from the internal regions of the polymer. These arabinoside fragments represent the major known structural motifs that comprise the arabinan segment of arabinogalactan and lipoarabinomannan. The presence of [14C]arabinose in both the internal and external regions of the [14C]arabinan suggests that polyprenylphosphate-arabinose is the major, and perhaps the only, donor of arabinosyl residues in mycobacteria.

Cell Wall↗
PubMed1997

Molecular weight abnormalities of the CTCF transcription factor: CTCF migrates aberrantly in SDS-PAGE and the size of the expressed protein is affected by the UTRs and sequences within the coding region of the CTCF gene.

CTCF belongs to the Zn finger transcription factors family and binds to the promoter region of c-myc. CTCF is highly conserved between species, ubiquitous and localised in nuclei. The endogenous CTCF migrates as a 130 kDa (CTCF-130) protein on SDS-PAGE, however, the open reading frame (ORF) of the CTCF cDNA encodes only a 82 kDa protein (CTCF-82). In the present study we investigate this phenomenon and show with mass-spectra analysis that this occurs due to aberrant mobility of the CTCF protein. Another paradox is that our original cDNA, composed of the ORF and 3'-untranslated region (3'-UTR), produces a protein with the apparent molecular weight of 70 kDa (CTCF-70). This paradox has been found to be an effect of the UTRs and sequences within the coding region of the CTCF gene resulting in C-terminal truncation of CTCF-130. The potential attenuator has been identified and point-mutated. This restored the electrophoretic mobility of the CTCF protein to 130 kDa. CTCF-70, the aberrantly migrating CTCF N-terminus per se, is also detected in some cell types and therefore may have some biological implications. In particular, CTCF-70 interferes with CTCF-130 normal function, enhancing transactivation induced by CTCF-130 in COS6 cells. The mechanism of CTCF-70 action and other possible functions of CTCF-70 are discussed.

Animals↗
PubMed1997

Active vs. passive methods of recruiting ethnic minority women to a health promotion program.

Ethnic minority women have been underrepresented in health promotion research. There is a need to develop effective methods of recruiting ethnic minority women to health promotion programs and research studies. This article evaluates several methods for recruiting ethnic minority women to a study of a telephone and mail intervention encouraging participation in a home-based walking program. One hundred twenty-six sedentary ethnic minority women between the ages of 25 and 55 were recruited using two types of approaches. Number of participants screened, number enrolled, and recruitment efficiency (ratio of number recruited/number screened) were assessed. "Active" recruitment, contacting targeted individuals in person, by phone, or by mail, yielded 236 screened and 29 recruited with a recruitment efficiency of 11%. "Passive" recruitment, informing the community through public notices and waiting for volunteers to call, yielded 151 screened and 97 recruited with a recruitment efficiency of 64%. Those recruited by active or passive methods did not differ by demographic characteristics, baseline psychosocial variables, or dropout rates. Passive recruits walked significantly more at five-month follow-up than active recruits. Passive recruitment may be more economical at the cost of potentially biased samples.

Adult↗
PubMed1997

Biosynthetic origin of mycobacterial cell wall galactofuranosyl residues.

SETTING: Mycobacterial galactofuran is essential to the linking of the peptidoglycan and mycolic acid cell wall layers. Galactofuran biosynthesis should thus be essential for viability. OBJECTIVE: The objective was to determine the pathway of galactofuranosyl biosynthesis and to clone a gene encoding an essential enzyme necessary for its formation. DESIGN: Specific enzymatic conversions involved in formation of galactopyranose and galactofuranose residues in other bacteria were tested for in Mycobacterium smegmatis. M. tuberculosis deoxyribonucleic acid (DNA) was identified by homology. RESULTS: It was shown that the de novo synthesis of the galactose carbon skeleton occurred in M. smegmatis by the transformation of UDP-glucopyranose to UDP-galactopyranose via the enzyme UDP-glucose 4-epimerase (E.C. 5.1.3.2). The N-terminal sequence of this enzyme was obtained after purification. The galactose salvage pathway enzyme, UDP-glucose-galactose-1-phosphate uridylyltransferase (E.C. 2.7.7.12), was also shown to be present. The critical biosynthetic transformation of the galactopyranose to galactofuranose ring form was shown to occur at the sugar nucleotide level via the enzyme UDP-galactopyranose mutase (E.C. 5.4.99.9). The M. tuberculosis DNA encoding this enzyme was sequenced, the gene expressed in Escherichia coli, and the expected enzymatic activity demonstrated. CONCLUSION: Galactofuranose biosynthesis can now be pursued as a potential drug target in M. tuberculosis.

Amino Acid Sequence↗
PubMed1997

Mycobacterial arabinan biosynthesis: the use of synthetic arabinoside acceptors in the development of an arabinosyl transfer assay.

Information on the biosynthesis of the D-arabinans of the cell wall of Mycobacterium tuberculosis is rapidly emerging, with the promise of new targets for drug development against tuberculosis. Accordingly, arabinosyl transferase assays were developed utilizing synthesized [1-14C]-beta-D-arabinofuranosyl-1-monophosphoryldecaprenol as donor and a variety of O- and S-alkyl arabinosides as acceptors. These were: alpha-D-Araf-(1-->5)-alpha-D-Araf-O- and -S-alkyl diarabinosides and alpha-D-Araf-(1-->5)-alpha-D-Araf-(1-->5)-alpha-D-Araf -O- and -S-alkyl triarabinosides. Whereas the O- and S-alkyl monosaccharide acceptors were inactive, the O- and S-alkyl disaccharide and the O- and S-alkyl trisaccharide acceptors ( 5) arabinosyl transferase and beta-D-arabinofuranosyl-1-monophosphoryldecaprenol: arabinan beta(1-->2) arabinosyl transferase. The beta(1-->2) arabinosyl transferase activity was more in evidence in the presence of the O-alkyl disaccharide acceptor, whereas both transferases were about equivalent in the presence of the S-alkyl trisaccharide acceptor. The tuberculosis drug, ethambutol, a known mycobacterial arabinosyl transferase inhibitor, was inactive within these arabinosyl transferase/acceptor based assay systems, supporting other evidence that a third activity, responsible for the formation of alpha1-->3 linkage, is the drug target.

Autoradiography↗
PubMed1997

The National Marital and Family Therapy Examination Program.

Examinations constitute one of the principal methods by which professions assess minimal competence in aspiring practitioners. The Examination in Marital and Family Therapy is used by most states which regulate the profession. This article provides the rationale for the examination program, describes its development and maintenance, and presents the knowledge base it samples. Administrative policies and procedures are also discussed as an aid to prospective licensure and certification candidates.

Certification↗
PubMed1996

Topography of cardiac ganglia in the adult human heart.

Published descriptions of the topography of cardiac ganglia in the human heart are limited and present conflicting results. This study was carried out to determine the distribution of cardiac ganglia in adult human hearts and to address these conflicts. Hearts obtained from autopsies and heart transplant procedures were sectioned, stained, and examined. Results indicate that the largest populations of cardiac ganglia are near the sinoatrial and atrioventricular nodes. Smaller collections of ganglia exist on the superior left atrial surface, the interatrial septum, and the atrial appendage-atrial junctions. Ganglia also exist at the base of the great vessels and the base of the ventricles. The right atrial free wall, atrial appendages, trunk of the great vessels, and most of the ventricular myocardium are devoid of cardiac ganglia. These findings suggest modifications to surgical procedures involving incisions through regions concentrated with ganglia to minimize arrhythmias and related complications. Repairs of septal defects, valvular procedures, and congenital reconstructions, such as the Senning and Fontan operations, involve incisions through areas densely populated with cardiac ganglia. The current standard procedure for orthotopic heart transplantation severs cardiac ganglia and their projections to nodal and muscular tissue. One modification of the current heart transplantation procedure, involving bicaval anastomosis, preserves atrial anatomy and the cardiac ganglia. Preservation of cardiac ganglia within the donor heart may provide additional neuronal substrate for intracardiac processing and targets for regenerating nerve fibers to the donor heart.

Adult↗
PubMed1996

Cold-hardiness of a laboratory colony of lone star ticks (Acari: Ixodidae).

The cold-hardiness of a lone star tick, Amblyomma americanum (L.), laboratory colony was characterized. Fed and unfed larvae, fed and unfed nymphs, and unfed adults did not survive exposure to -17 degrees C for 7 d. After an 8-d exposure to -10 degrees C, adults tolerated cold better than immatures and unfed specimens fared better than fed ticks. Exposing unfed 6-wk-old (postmolt) adult males and females to -15 degrees C for increasing intervals up to 2 h suggests that males were more tolerant to cold than were females. Half of all adults were alive 3 d after the 2-h low-temperature treatment. Males may have survived because of a significantly higher hemolymph osmotic pressure, although the solute concentration increased for both sexes after a 2-h exposure to 0 degree C. Acclimation to 5 degrees C for 7 d had no influence on supercooling points for unfed males and females, engorged nymphs and larvae, and eggs. None of the life stages survived supercooling, which strongly suggests that this species is freeze intolerant. Intolerance of immature stages to chilling may be a limiting factor in the northern distribution of lone star ticks in North America.

Animals↗
PubMed1996

Etoposide-cisplatin and thoracic radiation therapy salvage of incomplete responders to a noncisplatin induction regimen for limited and extensive small-cell carcinoma of the lung.

Our purpose was to determine the ability of an etoposide-cisplatin (EP )-based regimen to salvage patients with limited and extensive small-cell lung cancer who are incomplete responders to cyclophosphamide-Adriamycin-vincristine-etoposide (CAVE) chemotherapy, and to determine the ability of thoracic radiation therapy (TRT) to salvage CAVE and EP incomplete responders. Fifty-eight patients with small-cell lung cancer (33, limited disease; 25, extensive disease) were entered on this Phase II study between November 1984 and December 1987. Patients received three cycles of CAVE chemotherapy, followed by two cycles of CEPi (cyclophosphamide-etoposide-cisplatin (infusional) and two cycles of CE (cyclophosphamide-etoposide) in conjunction with TRT and prophylactic cranial irradiation (PCI). The overall response rate to CAVE was 62% [5% complete response (CR), 57% partial response (PR) + regression (REGR)]. Of the patients who failed to achieve a CR with CAVE, 81% responded to CEPi (44% CR, 36% PR). Of the patients who did not achieve a CR with either CAVE or CEPi, 89% responded to TRT (65% CR, 24% PR + REGR). For the 33 patients with limited disease, the median survival time and 2-year survival rate were 16.1 months and 24%, respectively. The corresponding figures for the 25 patients with extensive disease were 9.8 months and 4%, respectively. Eleven of these 25 patients were "downstaged" to "limited disease" with CAVE + CEPi and then received TRT + PCI + CE. Their median survival time and 2-year survival rate were 12.6 months and 9%, respectively. The EP-based regimen CEPi and TRT were able to convert 44 to 65% of patients to a complete response who had failed to do so with non-EP induction chemotherapy. This study supports the use of an EP regimen with TRT as initial therapy for newly diagnosed small-cell lung cancer.

Adult↗