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Biomedical subjects

L Stark

Publications and source records attributed to L Stark.

At least 19 recordsLinked to original sources
PubMed2006

A nucleic acid sequence-based amplification assay for real-time detection of norovirus genogroup II.

AIMS: To use molecular beacon based nucleic acid sequence-based amplification (NASBA) to develop a rapid, sensitive, specific detection method for norovirus (NV) genogroupII (GII). METHODS AND RESULTS: A method to detect NV GII from environmental samples using real-time NASBA was developed. This method was routinely sensitive to 100 copies of target RNA and intermittent amplification occurred with as few as 10 copies. Quantitative estimates of viral load were possible over at least four orders of magnitude. CONCLUSIONS: The NASBA method described here is a reliable and sensitive assay for the detection of NV. This method has the potential to be linked to a handheld NASBA device that would make this real-time assay a portable and inexpensive alternative to bench-top, lab-based assays. SIGNIFICANCE AND IMPACT OF THE STUDY: The development of the real-time NASBA assay described here has resulted in a simple, rapid (<1 h), convenient testing format for NV. To our knowledge, this is the first example of a molecular beacon based NASBA assay for NV.

Base Sequence↗
PubMed2005

Infection of human endothelial cells with Staphylococcus aureus induces transcription of genes encoding an innate immunity response.

Staphylococcus aureus is a gram-positive bacterium frequently isolated from patients with bloodstream infections. Endothelial cells (EC) play an important role in host defence against bacteria, and recent reports have shown that infection of EC with S. aureus induces expression of cytokines and cell surface receptors involved in activating the innate immune response. The ability of S. aureus to invade nonphagocytic cells, including EC, has been documented. However, the knowledge of the role of EC in pathogenesis of S. aureus infection is still limited. In this study, we investigate the gene-expression program in human EC initiated by internalized S. aureus, using microarray analysis. We found 156 genes that were differentially regulated at least threefold, using arrays representing 14,239 genes. Many of the upregulated genes code for proteins involved in innate immunity, such as cytokines, chemokines and cell adhesion proteins. Other upregulated genes encode proteins involved in antigen presentation, cell signalling and metabolism. Furthermore, intracellular bacteria survived for days without inducing EC death.

Cell Adhesion Molecules↗
PubMed2000

Incidental detection of a malignant hurthle cell carcinoma by Tc-99m sestamibi cardiac imaging.

A 60-year-old man reported chest pain and shortness of breath. His medical history was negative for myocardial infarction but positive for "mini strokes" and type 2 diabetes mellitus. Tc-99m sestamibi cardiac imaging revealed an abnormal focus of increased activity in the left lobe of the thyroid. Although no cardiac abnormalities were found, a I-123 thyroid scan subsequently showed a solitary hypofunctioning nodule involving the middle and inferior aspects of the left lobe of the thyroid, which fine-needle aspiration proved was a Hurthle cell carcinoma.

Adenocarcinoma↗
PubMed1997

Indications for surgical management of genitourinary tuberculosis.

The incidence of tuberculosis has risen in many parts of the world, and more attention is being focused on genitourinary tuberculosis (GT), the second most common extrathoracic form of tuberculosis. Although chemotherapy is the mainstay of treatment, ablative surgery as a first-line management may be unavoidable for sepsis or abscesses. In cases with hydronephrosis and progressive renal insufficiency caused by obstruction, renal drainage (by stenting or nephrostomy) must be performed immediately. In all other situations triple-drug chemotherapy should be undertaken for at least 6 months and stable conversion obtained before ablative or reconstructive surgery is planned. Nephrectomy or partial nephrectomy is indicated for nonfunctioning or poorly functioning kidneys, particularly if continuous flank pain or hypertension is present. Stenosis of the ureter usually can be managed by temporary stenting and adjuvant corticosteroid therapy. Today the indications for augmentation are rare, but bladder replacement may be combined with ureter replacement using segments of intestine.

Adolescent↗
PubMed1997

The use of scheduled awakenings to eliminate childhood sleepwalking.

Evaluated the use of scheduled awakenings to eliminate sleepwalking using a noncurrent multiple baseline design across three subjects with persistent sleep-walking. Treatment procedure involves having parents awaken children several hours after they go to sleep and just before the typical time of the sleepwalking episode. This intervention proved immediately successful in eliminating sleep-walking in all three children. Treatment effects were maintained at 3 and 6 months posttreatment. Implications for intervention and future research are discussed.

Behavior Therapy↗
PubMed1996

On evolutive systems and the initial evolution of structure and function.

As an instrument for the study of the early stages of evolution, we introduce evolutive systems, defined as systems that have the capacity to evolve given appropriate conditions in their environment. They consist of building blocks (e.g. monomers) that are either stable or in steady supply, and of transient assemblies (e.g. polymers) that are entities of great variety, some of which are capable of function. Evolution leads to the accumulation of structure within the transient assemblies during repeated cycles of disintegration (partial or total) and reassembly, on account of the selective advantages associated with transient assembly functions. Transient assemblies must be either inherently unstable or subject to disintegration by agents in their environment. Evolutive systems must have access to a negentropy input in the form of energy in packets larger than typical thermal energies. Reproduction, although not a prerequisite, greatly affects the capacity of evolutive systems to evolve, and thus can be expected to appear in an evolutive system if at all possible. Similarly, functions that require the expenditure of negentropy (for example mobility, breathing, circulation, sensing, communicating, etc.) are not prerequisites for evolution, but can be expected to become established in evolutive systems during evolution through the selective advantages that they confer. A computer-based evolutive automaton is used to explore possible evolutionary scenarios. In the presence of spatial and temporal inhomogeneities, one can construct a multitude of evolutionary scenarios through which various functions, such as the operation of genetic code, can become established within the evolutive automaton. This variety of possible evolutionary scenarios is all the more remarkable because the automaton does not include many important physical processes that would be present in a real system and would greatly multiply the number of possible evolutionary mechanisms and scenarios. Some evolutionary mechanisms are based on survival related selection, while others are based on generation related selection. Previously explored scenarios for the initiation of life have been based mostly on generation related selection. In this paper, we give particular emphasis to survival related selection which is more general in that it does apply to structures and functions related to reproduction but, unlike generation related selection, it is not limited to them. Some of the most basic features of terrestrial living systems can be seen either as prerequisite features of an evolutive system (such as the mortality of living organisms, instability of biological polymers, imperfect reproduction caused by mutations, and the need for a negentropy input) or as features that one can reasonably expect to become established in an evolutive system (such as reproduction and the multitude of living functions that require expenditure of negentropy). This suggests the possibility that an independent definition of living systems may not be necessary if features of living systems substantially overlap with features that one may expect to find in evolutive systems.

Animals↗
PubMed1995

Evidence for a global scanpath strategy in viewing abstract compared with realistic images.

Scanpaths, the repetitive sequences of saccadic eye movements, occurred when subjects viewed slide projections of both realistic and abstract art. Variance analysis demonstrated that global/local eye movement indices were lower for local scanning by professional art viewers who relied on more global viewing, particularly in abstract images. Non-professional, unsophisticated subjects carried their local scanpath patterns from realistic images on to abstract images. The blink rate of professional subjects viewing abstract images was also significantly lower, indicating increased visual effort. Non-professional viewers showed no difference in blink rates.

Adult↗
PubMed1995

Hysteresis in accommodation.

Under certain conditions the accommodative response is not a simple function of accommodative stimulus, but depends as well upon the history of the stimulus. Experimental evidence points to multiple mode control of accommodation as being responsive: a high-gain feedback control mode responds to blur; a second mode causes a drift to bias set level when visual stimuli are removed. We extend a model consistent with these results and use it to predict the results of a new experimental paradigm, 'pushdown' accommodation. Finally, we extend the model to a third mode of behaviour, schematic accommodation, which encompasses instrument myopia, proximal accommodation and voluntary accommodation.

Accommodation, Ocular↗
PubMed1995

Long-term clinical and prostate-specific antigen follow-up in 500 patients treated with radiation therapy for localized prostate cancer.

During a 14-year period, 500 consecutive patients having localized prostate cancer were treated with external beam radiotherapy with curative intent. Patients were staged according to the Whitmore-Jewett and TNM systems. Median follow-up for all patients was 69 months. Local recurrence included failures detected by rectal examination and/or prostate biopsy. Progressively elevated prostate-specific antigen (PSA) values at follow-up with no evidence of systemic disease also was considered a local treatment failure. Overall 5- and 10-year survival rates were 65% and 37%, respectively. Cause-specific 5- and 10-year survival rates were 79% and 55%, respectively. Five- and 10-year local control rates for all patients were 72% and 52%, respectively. No patient with a T1 a tumor failed locally. When follow-up PSA data were included in control criteria, 10-year local control rates for patients with T1b, T2a, and T2b-T4 tumors were 66%, 55% and 44%, respectively. If only an abnormal rectal examination and/or a positive post-treatment biopsy was considered as evidence of local failure, control rates were significantly better. Approximately one third of the study patients had died of cancer or intercurrent disease before the PSA test was used routinely. Of the 244 patients (49%) for whom follow-up PSA values were available, 116 had a normal post-treatment PSA with no evidence of disease; 94 were alive and 22 died with no evidence of prostate cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Ileal bladder augmentation combined with ileal ureter replacement in advanced urogenital tuberculosis.

We report a case of active tuberculosis associated with a right nonfunctioning kidney and nearly total loss of bladder capacity. Percutaneous nephrostomy and right nephroureterectomy were performed while the patient was undergoing triple drug therapy. Definitive surgical treatment consisted of ileal bladder augmentation and ileal ureter replacement. Normal urodynamics of the upper urinary tract and normal voiding with complete return of bladder capacity were achieved. Metabolic acidosis was treated successfully by sodium hydrogen carbonate.

Aged↗
PubMed1994

Comparison of chickens and pheasants as sentinels for eastern equine encephalitis and St. Louis encephalitis viruses in Florida.

Pheasants and chickens were compared as sentinels for monitoring the transmission of arboviruses of public health significance in Florida during 1991-93. Results suggest that pheasants are better sentinels for eastern equine encephalitis (EEE) virus. They detected virus transmission 3-6 weeks earlier in epizootic years, 2-4 times more frequently during the season, and twice as many birds within a flock seroconverted during a given week. Pheasants detected virus transmission at 2 sites during 2 interepizootic years when chickens failed. Although pheasants detected St. Louis encephalitis (SLE) virus activity somewhat later than did chickens, they had greater seroconversion rates than did chickens. Although both bird species can be used to monitor EEE and SLE viruses, pheasants are more sensitive than chickens as sentinels for EEE virus and as sensitive as chickens as sentinels for SLE virus.

Animals↗
PubMed1993

Level dependent signal flow in the light pupil reflex. I. Latency of time domain responses to transient stimuli.

Latency of pupillary responses to light stimuli are smaller for larger steps of light, and larger for smaller steps of light (Alpern 1954; Lowenstein et al. 1964; Lee et al. 1969; Terdiman et al. 1969; Cibis et al. 1977; and many others). Miller and Thompson (1978), however, reported negligible change in pupil cycle time (period of high gain instability oscillations) with increased mean brightness. Sandberg and Stark (1968) reported a negligible reduction in phase lag of pupillary responses to sinusoidal light stimuli as the modulation coefficient (m) increased. To resolve the inconsistency between the well-documented dependence of latency upon brightness, and the apparent absence of level dependence in the phase characteristics (as reflected directly in the responses to sinusoidal stimuli and indirectly in pupil cycle time experiments) we measured: 1. Latency to step stimuli of light, 2. Phase of responses to sinusoidal light stimuli and 3. Period (pupil cycle time) of high gain instability oscillations. The dependence of pupillary latency upon stimulus level (both light and accommodation) and the interaction between accommodation and light responses were investigated. We show that most of the level dependence of light-pupil latency resides in the afferent path. In the companion papers, we demonstrate that: 1. Phase of pupillary response to sinusoidal light stimuli is reduced by increased mean light level, but is independent of pupil size and accommodative stimulus level; and 2. The period of high gain oscillations is shown to decrease with increased mean light level.(ABSTRACT TRUNCATED AT 250 WORDS)

Accommodation, Ocular↗
PubMed1993

Level dependent signal flow in the light pupil reflex. III. Phase velocity in high gain instability oscillations.

The pupil can be excited to sustained oscillations under high gain feedback conditions. The period of these oscillations (cycle time) is reduced by increased average light level by an amount commensurate with reductions in phase lag reported in the companion paper (Myers et al. 1991b). A mathematical model of this phenomenon is used to unify and clarify experimental data presented here and in the literature.

Cybernetics↗
PubMed1993

Venous pressure in idiopathic varicocele.

In 27 patients with clinically identified idiopathic left varicocele, a retrograde venography and a combined pressure measurement in the vena cava, vena renalis and vena spermatica was performed. During Valsalva maneuver the pressure values increased. We could not confirm increased pressure values in the left renal vein dependent on the patient's position. There were no increasing pressure gradients between vena renalis and vena cava in erect position. Therefore an elevated pressure in the left renal vein and especially the 'upper nutcracker' does seem to be of at least limited importance for the pathogenesis of idiopathic varicocele.

Adolescent↗
PubMed1993

[Organ saving therapy of bilateral testicular tumor].

Of 368 patients with unilateral testicular cancer, 12 (3.3%) suffered from a second malignant germ cell tumor; five tumors occurred synchronously, seven were treated by bilateral orchiectomy, five were treated by unilateral organ sparing surgery with enucleation of the germ cell tumor in a pilot study. Enucleation was performed for four seminomas and one embryonal carcinoma; an associated carcinoma was found in situ in three cases. The average follow-up time for patients treated conservatively is 22 months; no local recurrence has been detected. Testosterone synthesis is sufficient to obtain normal serum androgen levels. Organ sparing surgery for testicular cancer is possible if the following prerequisites are met: pT 1-tumor, no infiltration of the rete testis, biopsies of the tumor bed are negative, biopsies from peripheral parenchyma are taken and any associated carcinoma in situ is irradiated with 20 Gy.

Combined Modality Therapy↗
PubMed1992

Treatment of non-small cell lung cancer with external beam radiotherapy and high dose rate brachytherapy.

Between August 1985 and September 1989, 62 patients with medically inoperable or surgically unresectable, non-small cell lung cancer were treated with both external beam radiotherapy and high dose rate bronchial brachytherapy. Treatment consisted of external beam radiotherapy (5000-6000 cGy in 5-6 1/2 weeks) and weekly high dose rate bronchial brachytherapy (three to five fractions, 500 cGy at 1 cm from the source) delivered either concurrently or sequentially. Median survival for all patients was 13 months (m). Stage I and Stage IIIA-B patients had median survivals of 20 m and 10 m, respectively. Patients without nodal disease (No) had a significantly longer median survival compared to patients with regional node metastases (N1-3), 17 m versus 9 m. A total of 54 patients were evaluable for local tumor control analysis. Local tumor control was achieved in six of eight patients who had a normal pre-treatment radiograph. Patients with measurable tumor on the pre-treatment radiograph and negative regional nodes had local tumor control in eight of twenty-two (36%) cases. In patients with regional lymphadenopathy, loco-regional tumor control was achieved in four of eight cases. Additionally, there were sixteen patients with non-measurable tumor due to associated effusion, atelectasis and/or infiltrate. Four of these (25%) were considered to have local tumor control. Of 60 evaluable patients, there were nine occurrences of fatal hemorrhage, one of whom was disease-free (NED) at autopsy. The remaining eight patients had either clinical or pathological evidence of recurrent or persistent tumor. Patients who had follow up bronchoscopies were found to have varying degrees of concentric narrowing in the treated areas. One such patient had total lung collapse with no evidence of tumor. While this form of treatment may yield high local control rates in earlier stages, this study suggests the potential risk of fatal complication. Additional studies are warranted to further investigate the use of this modality in the treatment of lung cancer.

Adenocarcinoma↗
PubMed1992

Accommodation on downward gaze.

A study was conducted with the purpose of examining the possible effects of vertical and horizontal eye movements upon accommodation. A special Badal stimulator was made which was vertically rotatable around the center of an eye. The stimulator was attached to the Three-Dimensional Optometer III (TDOIII), which could measure accommodation, eye movement, and pupil diameter simultaneously. The reliability of the TDOIII measurements of accommodation was checked by comparing with a stigmatoscope measurement. Three young males served as subjects. A small but definite near accommodation was measured dynamically in association with vertical eye movement. We believe this to be the first report of this finding. The amount of near accommodation with downgaze showed a tendency to decrease when the target was brought near.

Accommodation, Ocular↗