Biomedical subjects

Z Syed

Publications and source records attributed to Z Syed.

5 recordsLinked to original sources

PubMed2001

1-octen-3-ol isolated from bont ticks attracts Amblyomma variegatum.

Volatiles from various life-stages of the bont ticks Amblyomma variegatum and A. hebraeum were collected by using solid-phase microfibers and charcoal traps. An octenol isomer was found to be a major constituent of most of the tick material sampled and was identified as 1-octen-3-ol by gas chromatography-mass spectrometry and by using antenna of the tsetse fly Glossina brevipalpis in gas chromatography-linked antennogram detection. Release of this compound increased during molt to adulthood and following mechanical disturbance of adult ticks. (R)-(-)-1-Octen-3-ol and racemate 1-octen-3-ol both induce an increase in upwind walk to the odor source from A. variegatum in an airstream on a servosphere. Volatiles from tick exuviae plus feces and from dead ticks also attracted A. variegatum, suggesting that 1-octen-3-ol may contribute to the aggregation response of Amblyomma spp. on such substrates. 2,6-Dichloroanisol and 2,5-dimethylpyrazine also were detected in volatiles from the ticks but induced no behavioral responses on the servosphere. The suspected tick pheromone component, 2,6-dichlorophenol, was detected from A. variegatum adults cut into pieces but had no effect on the behavior of A. variegatum on the servosphere at a range of doses.

Animals↗

PubMed2001

The occurrence of sleep-disordered breathing among patients with head and neck cancer.

OBJECTIVE: To identify the incidence of obstructive sleep apnea (OSA) in patients treated for head and neck cancer. Obstructive sleep apnea is a relatively common and highly morbid condition that affects 9.1% of male and 4% of female middle-aged adults.1 Patients who have been successfully treated for head and neck cancer may often have a partially obstructed upper airway which is functional during the day, but collapses during sleep. STUDY DESIGN/METHODS: Twenty-four patients successfully treated for tumors of the tongue-base, pharynx, or supraglottic larynx were enrolled. Through OSA-related questionnaires, physical examination, and polysomnography, the incidence of OSA in this patient population was determined and compared with that of the general population. RESULTS: The incidence of OSA (91.7%) in this head and neck cancer patient population was found to be significantly (P =.001) higher than that of the general population. (In a random sampling of middle-aged adult males between the ages of 30 and 60 years old with a respiratory disturbance index (RDI) >15, the prevalence was previously reported to be 9.1%.1) Sixteen of 24 patients (72.7%) had clinically defined symptoms of sleep apnea. Ten of 24 patients (41.7%) received radiation therapy; all had an RDI >15. Eleven of the 14 patients (78.5%) who did not receive radiation therapy also had an RDI >15. Eight patients (33.3%) continue to regularly use continuous positive airway pressure with significant improvement in symptoms. CONCLUSIONS: Identification and treatment of OSA may be an important factor in improving quality of life for patients with head and neck cancer.

Body Mass Index↗

PubMed2000

ICD waveform optimization: a randomized, prospective, pair-sampled multicenter study.

The theoretical tissue model-based estimates of phase 1 and phase 2 duration of biphasic waveforms are considerably shorter than the pulse widths currently used in ICDs with standard tilt. This study used a tissue resistance/capacitance (RC) model to identify optimal biphasic pulse widths. By paired step-down defibrillation threshold (DFT) testing, the efficacy of standard versus "tuned" biphasic waveforms was evaluated in 91 patients. Standard waveforms consisted of a phase 1 set to 65% tilt and phase 2 = phase 1. The tuned waveform was based on an RC model of membrane characteristics with a time constant of 3.5 ms. The optimal phase 1 truncation point is at the peak of membrane response. The optimal phase 2 duration ends with a membrane response near or just below 0. In paired analysis, no significant differences were found in DFT or impedance between standard and tuned waveforms. In patients with DFTs > 400 V, the tuned waveform lowered the DFT by an average of 38 V (P < 0.05). Multivariate analyses showed a significant inverse relationship between DFT and impedance (P < 0.001). As impedance increased, the tuned waveform was associated with DFTs comparable to the standard waveform with shorter pulse duration and lower delivered energy. No single tilt value allowing an easy calculation of delivered energy was related to ICD waveform efficacy. The use of ICDs with tuned optimal pulse durations offer a greater flexibility of choice for patients with high DFTs.

Aged↗

PubMed1994

Kinesin and tau bind to distinct sites on microtubules.

We have used a fluorescent derivative of kinesin, AF-kinesin (kinesin conjugated with 5-(iodoacetamido)fluorescein), to investigate the binding site of kinesin on microtubules and to compare this site with that to which tau binds. Microtubules saturated with tau will bind AF-kinesin in the presence of the ATP analogue, 5'-[beta,gamma-imino]triphosphate (AdoPP[NH]P). This shows that there are distinct binding sites for the two proteins. Further evidence comes from digestion studies where taxol-stabilised microtubules were treated with subtilisin, resulting in the cleavage of C-terminal residues from both the alpha- and beta-tubulin subunits. These treated microtubules can no longer bind tau, but are able to bind AF-kinesin in the presence of AdoPP[NH]P. Finally, AF-kinesin will support the gliding of subtilisin-digested microtubules in the presence of ATP at rates comparable to those obtained with non-digested microtubules. These results show directly that the binding site for kinesin is outside the C-terminal region of tubulin that is removed by subtilisin and is distinct from the binding site of tau.

Adenylyl Imidodiphosphate↗

PubMedDate not supplied

Skeletal effects of primary hyperparathyroidism.

OBJECTIVE: To review the effect of primary hyperparathyroidism on bone mass and occurrence of fractures as well as the advances in medical management of this relatively common condition. METHODS: We conducted a MEDLINE search of peer-reviewed publications for the period from 1960 to 1999. Studies reviewed were those that evaluated bone mass and fracture risk in primary hyperparathyroidism in both male and female populations. Studies that assessed intervention with hormone replacement therapy, bisphosphonates, calcimimetic agents, and surgical treatment and their effect on bone mass and fracture were also reviewed. Preference was given to prospective studies, but retrospective, cross-sectional, and case-control studies were also evaluated. RESULTS: Most densitometry studies completed to date have been limited by their design. Some cross-sectional studies that used both single-photon absorptiometry and dual-energy x-ray absorptiometry have demonstrated preferential bone loss at cortical skeletal sites. Bone density seems to be relatively well preserved at cancellous bone sites. The absence of large prospective controlled trials makes it difficult to evaluate fracture incidence associated with hyperparathyroidism. Retrospective and case-control studies have found conflicting results relative to fracture incidence in patients with primary hyperparathyroidism. Parathyroidectomy has been shown to be of value in improving bone mineral density at both the lumbar spine and the femoral neck. Hormone replacement therapy in postmenopausal women with primary hyperparathyroidism has also been effective in improving bone mineral density and decreasing bone turnover. Bisphosphonates are currently being evaluated for effectiveness in improving bone mineral density and reducing the risk of fracture. Early results with alendronate treatment have demonstrated improvements in bone mass. Calcimimetic agents are a new treatment option that may become useful in the medical management of primary hyperparathyroidism. CONCLUSION: Although conflicting findings have been reported, bone loss has been noted in patients with primary hyperparathyroidism, especially at cortical skeletal sites. Medical management does not seem to be associated with increased morbidity or mortality in patients with asymptomatic primary hyperparathyroidism. Bone densitometry is advised, particularly for monitoring of bone mass at the midradius or femoral neck, in patients with primary hyperparathyroidism.

Bone Density↗