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Biomedical subjects

R E Lee

Publications and source records attributed to R E Lee.

At least 37 records · Page 2Linked to original sources
PubMed2000

Extreme resistance to desiccation in overwintering larvae of the gall fly Eurosta solidaginis (Diptera, tephritidae).

During winter, larvae of the goldenrod gall fly Eurosta solidaginis are exposed for extended periods to severe low ambient temperatures and low humidities within plant galls. The resistance of these larvae to desiccation at various temperatures and humidities, the transition (critical) temperature, and the effects of treatment with organic solvents on the larval rates of water loss and on changes in osmolality during desiccation were examined. The water loss rates of the flesh fly Sarcophaga crassipalpis under desiccating conditions were also measured. The water permeability of the cuticle of E. solidaginis larvae was very low (0.038 microgram h(-1 )cm(-2 )Pa(-1) at 20 C and 4% relative humidity) compared with that of larvae of other species. The value for E. solidaginis is equivalent to that of the very drought-resistant larvae of the tenebrionid beetle Tenebrio molitor (0.038 microgram h(-1)cm(-2)Pa(-1) at 30 C). In contrast, the permeability of larvae of the flesh fly Sarcophaga crassipalpis at 20 C and 4 % relative humidity was 0.331 microgram h(-1) cm(-2)Pa(-1). The thermal dependence of the cuticular permeability increased with temperature by approximately 0.0010 +microgram h(-1) cm(-2)Pa(-1) C(-1) in the interval between 4 and 40 C. At the transition temperature of 40 C, the thermal dependence of the permeability increased abruptly to 0.0400 microgram h(-1)cm(-2)Pa(-1) C(-1). Larvae treated with hexane and acetone remained remarkably resistant to water loss. However, treatment with chloroform:methanol increased the water loss rate approximately 25-fold. During desiccation at 4 C and 4% relative humidity for 21 days, E. solidaginis larvae showed a mass loss of 18.5+/-4.4 % (mean +/- s.e.m., N=6). Animals dried under the same conditions over the same period showed a haemolymph osmolality of 851+/-75 mosmol kg(-1) (N=4). Larvae freshly removed from the galls showed a haemolymph osmolality of 918+/-67 mosmol kg(-1)(N=3). A higher osmolality in the dried compared with the fresh larvae would have been expected. The present observation suggests that important ions in the haemolymph may have been excreted or rendered osmotically inactive during desiccation.

Animals↗
PubMed2000

Identification of ice-nucleating active Pseudomonas fluorescens strains for biological control of overwintering Colorado potato beetles (Coleoptera: Chrysomelidae).

Laboratory studies were conducted to identify ice-nucleating active bacterial strains able to elevate the supercooling point, the temperature at which freezing is initiated in body fluids, of Colorado potato beetles, Leptinotarsa decemlineata (Say), and to persist in their gut. Adult beetles fed ice-nucleating active strains of Pseudomonas fluorescens, P. putida, or P. syringae at 10(6) or 10(3) bacterial cells per beetle had significantly elevated supercooling points, from -4.5 to -5.7 degrees C and from -5.2 to -6.6 degrees C, respectively, immediately after ingestion. In contrast, mean supercooling point of untreated control beetles was -9.2 degrees C. When sampled at 2 and 12 wk after ingestion, only beetles fed P. fluorescens F26-4C and 88-335 still had significantly elevated supercooling points, indicating that these strains of bacteria were retained. Furthermore, beetle supercooling points were comparable to those observed immediately after ingestion, suggesting that beetle gut conditions were favorable not only for colonization but also for expression of ice-nucleating activity by these two strains. The results obtained from exposure to a single, low dose of either bacterial strain also show that a minimum amount of inoculum is sufficient for establishment of the bacterium in the gut. Persistence of these bacteria in Colorado potato beetles long after ingestion was also confirmed using a polymerase chain reaction technique that detected ice-nucleating active bacteria by virtue of their ina genes. Application of these ice-nucleating active bacteria to elevate the supercooling point of this freeze-intolerant insect pest could significantly reduce their winter survival, thereby reducing local populations and, consequently, crop damage.

Animals↗
PubMed2000

Trans rectal ultrasound guided radioactive seed implant: the Sumter experience.

108 patients were treated between 1/06/97 and 7/19/99. Ages ranged from 53 years to 82 years. Pretreatment PSA ranged from 4.0 to 34.6 and post treatment PSA from 0 to 7.3. Given the fact that carcinoma of the prostate is a relatively slow growing tumor and that long survival times are not uncommon even in the face of relatively advanced disease, our treatment team believes that the preferred method of treatment in otherwise healthy patients who have a 20 year life expectancy is radical surgery. We do believe that brachytherapy has a role in the treatment of organ-confined disease and may possibly be proven to be as effective as surgery; however, until there is at least 15-year data, it cannot be considered as the primary treatment of choice in young men. The senior author has stressed the term "treatment team" in this paper for a reason. We sincerely believe that the best results for our patients are obtained when we approach the treatment of the patient as a unified team that makes use of our individual talents and training for the good of the patient as a whole. Each member of the team performs the procedures that he is best trained to do, and we are consistent in our approach and advice to our patients regardless of our disciplines.

Adenocarcinoma↗
PubMed1999

Inoculative freezing by environmental ice nuclei in the freeze-tolerant wood frog, Rana sylvatica.

Efficacy of inoculative freezing by ice nuclei in a simulated winter environment was studied in the wood frog (Rana sylvatica), a freeze-tolerant species that overwinters on the forest floor beneath organic detritus. Adult frogs were confined to plastic canisters and cooled to -2 degrees C over 24 hr with their ventral skin in contact with substrate (humic soil hydrated to 40, 10, or 5%, or soil/peat mixture hydrated to 20 or 10%, w/w), or their dorsal skin in contact with damp leaf mould. Whereas only 20% of control frogs cooled in dry, plastic canisters froze, freezing occurred in nearly all (98%) frogs contacting soil or leaf mould. Inoculation was briefly delayed in frogs exposed to drier substrates. Frogs exposed to an unfreezable substrate (humic soil, 5% moisture) themselves froze, apparently due to the action of constituent nuclei which commonly occur in natural materials. Although the surface over which inoculation can occur is greater in larger frogs, inoculation susceptibility was not correlated with body mass in our frogs (mean +/- SE body mass = 14.0 +/- 0.2 g; range, 9.8-17.8 g). We conclude that the high susceptibility to inoculative freezing in R. sylvatica, which is conferred by its moist, highly permeable integument, promotes freeze tolerance by ensuring that inoculation commences at relatively high temperatures.

Animals↗
PubMed1999

Electrophysiological and ultrastructural correlates of cryoinjury in sciatic nerve of the freeze-tolerant wood frog, Rana sylvatica.

We investigated function and ultrastructure of sciatic nerves isolated from wood frogs (Rana sylvatica) endemic to the Northwest Territories, Canada, following freezing at -2.5 degrees C, -5.0 degrees C, or -7.5 degrees C. All frogs frozen at -2.5 degrees C, and most frogs (71%) frozen at -5.0 degrees C, recovered within 14 h after thawing began; however, frogs did not survive exposure to -7.5 degrees C. Sciatic nerves isolated from frogs frozen at -7.5 degrees C were refractory to electrical stimulation, whereas those obtained from frogs surviving exposure to -2.5 degrees C or -5.0 degrees C generally exhibited normal characteristics of compound action potentials. Frogs responded to freezing by mobilizing hepatic glycogen reserves to synthesize the cryoprotectant glucose, which increased 20-fold in the liver and 40-fold in the blood. Ultrastructural analyses of nerves harvested from frogs in each treatment group revealed that freezing at -2.5 degrees C or -5.0 degrees C had little or no effect on tissue and cellular organization, but that (lethal) exposure to -7.5 degrees C resulted in marked shrinkage of the axon, degeneration of mitochondria within the axoplasm, and extensive delamination of myelin sheaths of the surrounding Schwann cells.

Action Potentials↗
PubMed1999

Association of adhesive macromolecules with terminal sprouts at the neuromuscular junction after botulinum treatment.

Small quantities of botulinum toxin (BTX) are useful in the treatment of certain movement disorders, such as laryngeal spasmodic dysphonia, blepharospasm, and cervical dystonia. However, the corrective paralytic effects of BTX are only temporary, in part because of the formation of remodeled neuromuscular junctions. Here, we questioned whether various factors within and near the neuromuscular junction could contribute to the remodeling seen after BTX treatment. BTX was injected subcutaneously in the region of the levator auris longus muscle. At 1-week intervals, levator auris longus muscles were removed and examined histochemically. As previously described, BTX treatment results in a progressive elongation of end plates. The neural cell adhesion molecule was not associated with the elongated end plates but was associated with the BTX-induced nerve sprouts after long intervals (3 to 4 weeks). Similarly, after BTX, laminin-1 (composed of alpha 1, beta 1, and gamma 1 chains) reactivity was associated with the nerve sprouts, but not with the end plates. Laminin beta 2 reactivity at the end plate dispersed somewhat within 1 week but remained diffusely associated with the elongating end plates for up to 5 weeks. Together these results suggest that neural cell adhesion molecule and laminins may participate in the sprouting observed after BTX treatment and that alterations in laminin beta 2 expression may participate in initial loss of contacts.

Animals↗
PubMed1998

Freeze duration influences postfreeze survival in the frog Rana sylvatica.

Survival, cryoprotection, and the time course for recovery of vital functions were studied in autumn-collected juvenile wood frogs (Rana sylvatica) following freezing at -1.5 degrees C for various periods. Frogs readily tolerated freezing for 3 or 9 d, but only 50% survived a 28-d freezing trial. Generally, the postfreeze return of vital functions (vascular circulation, pulmonary breathing, righting reflex, jumping reflex) occurred later in frogs frozen for longer periods. Augmenting endogenous levels of the cryoprotectant glucose (via injections) prior to freezing substantially increased freeze endurance, as these frogs had excellent survival after remaining frozen for as long as 49 d. The improved freeze endurance of glucose-loaded frogs apparently was not associated with a reduction in ice content but rather may reflect the greater availability of energy substrate needed to support metabolism of frozen ischemic tissues.

Animals↗
PubMed1998

Cryopreservation of spermatozoa from freeze-tolerant and -intolerant anurans.

Spermatozoa of the freeze-tolerant wood frog (Rana sylvatica) were used to develop a general protocol for the frozen storage of amphibian spermatozoa. Tolerance of spermatozoa to cryoprotective agents and freezing in suspension (-80 degrees C) was determined from rates of sperm lysis and dual-fluorochrome vital dye assays. We tested the efficacy of four cryoprotectants (Me2SO, methanol, glycerol, and ethylene glycol), two supplements (fetal bovine serum or glutathione), and combinations of these cryoprotectants and supplements. Me2SO and fetal bovine serum were the most effective cryoprotectant and supplement, respectively, in reducing sperm lysis. Vital dye assays showed that viability was greatest for spermatozoa treated with both Me2SO and fetal bovine serum. Thus, this combination was used to cryopreserve spermatozoa from the freeze-intolerant anurans, Rana pipiens and Bufo americanus. Recovery of viable spermatozoa was significantly greater for R. sylvatica (mean +/- SE = 81.2 +/- 9.6%) than for R. pipiens (59.0 +/- 2.8%) and B. americanus (47.8 +/- 4.1%), perhaps owing to inherent factors promoting its freeze tolerance. Nonetheless, our results support the feasibility of using gamete cryopreservation techniques in programs aimed at the captive propagation of amphibians.

Adaptation, Biological↗
PubMed1998

Algorithm for the diagnosis and management of asthma: a practice parameter update: Joint Task Force on Practice Parameters, representing the American Academy of Allergy, Asthma and Immunology, the American College of Allergy, Asthma and Immunology, and the Joint Council of Allergy, Asthma and Immunology.

This algorithm on the diagnosis and treatment of asthma is intended to complement and update the previously published Practice Parameters for the Diagnosis and Treatment of Asthma. Both documents were developed by the Joint Task Force on Practice Parameters, representing the AAAAI, ACAAI, and the JCAAI. The authors of this asthma algorithm have attempted to include all the elements essential for the diagnosis and care of patients with asthma. Every effort was made to keep the algorithm clear and concise, yet thorough and complete (Fig 1). Each component of the algorithm is elaborated further in a brief annotation. For further discussion, the reader is referred to the more extensive Practice Parameters for the Diagnosis and Treatment of Asthma.

Acute Disease↗
PubMed1998

Mechanisms involved in the intrinsic isoniazid resistance of Mycobacterium avium.

Isoniazid (INH), which acts by inhibiting mycolic acid biosynthesis, is very potent against the tuberculous mycobacteria. It is about 100-fold less effective against Mycobacterium avium. This difference has often been attributed to a decreased permeability of the cell wall. We measured the rate of conversion of radiolabelled INH to 4-pyridylmethanol by whole cells and cell-free extracts and estimated the permeability barrier imposed by the cell wall to INH influx in Mycobacterium tuberculosis and M. avium. There was no significant difference in the relative permeability to INH between these two species. However, the total conversion rate in M. tuberculosis was found to be four times greater. Examination of in vitro-generated mutants revealed that the major resistance mechanism for both species is loss of the catalase-peroxidase KatG. Analysis of lipid and protein biosynthetic profiles demonstrated that the molecular target of activated INH was identical for both species. M. avium, however, formed colonies at INH concentrations inhibitory for mycolic acid biosynthesis. These mycolate-deficient M. avium exhibited altered colony morphologies, modified cell wall ultrastructure and were 10-fold more sensitive to treatment with hydrophobic antibiotics, such as rifampin. These findings may significantly impact the design of new therapeutic regimens for the treatment of infections with atypical mycobacteria.

Bacterial Proteins↗
PubMed1998

The marital and family therapy examination program: a survey of participants.

Participants in the Examination in Marital and Family Therapy between November 1994 and May 1996 were surveyed to ascertain who took the examination, how they prepared for it, whether they thought that it was fair, and how these variables related to scores. Two-thirds of the respondents were female. Most were taking the examination for the first time, were relatively young, were Caucasian, and spoke English as their primary language. They primarily practiced marital and family therapy and had completed master's level university programs in marital and family therapy, counseling, and psychology. Most were sitting for the examination relatively soon after completing their training in marital and family therapy. Individual study was the preparation method of choice for half of the sample. Demographic variables had a modest but ambiguous effect on test score. Educational background had none. However, a relatively short latency between graduation and examination was related to a higher score, as was the use of multiple preparation procedures. With regard to fairness, the participants largely agreed that the examination was moderately difficult, but that the problems were realistic and they had enough time to complete the test.

Adult↗
PubMed1998

Biological ice nucleation and ice distribution in cold-hardy ectothermic animals.

For many ectotherms, overwintering survival depends on the avoidance or regulation of ice nucleation and growth within their body fluids. Freeze avoidance via supercooling plays an important role in the cold hardiness of many small species, particularly terrestrial arthropods, that do not survive the freezing of their body fluids. In contrast, mechanisms that limit supercooling and initiate freezing at relatively high temperatures promote survival of the few invertebrates and vertebrates that tolerate freezing. These mechanisms include inoculative freezing, which results from contact with ice in the environment, and various ice nucleating proteins, microbes, and crystalloid compounds. In freeze-tolerant ectotherms, cold hardiness is influenced by complex, seasonally changing interactions among physiological factors, ice nucleators, and the physical microenvironment. Extraorgan sequestration of ice is a major adaptation of freeze tolerance. For most freeze-tolerant species, ice growth is primarily restricted to extracellular compartments; however, intracellular freezing also occurs in some species.

Adaptation, Physiological↗