Biomedical subjects

T Wang

Publications and source records attributed to T Wang.

At least 217 records · Page 12Linked to original sources

PubMed2000

Coupling of solvent semimicroextraction with capillary electrophoresis using ethyl acetate as sample matrix.

This paper reports a strategy to couple liquid-liquid semimicroextraction (LLsME) with capillary electrophoresis (CE) based on a newly introduced on-column decomposable sample matrix, ethyl acetate (EA). LLsME was performed in volumetric flasks of 100 mL. Samples containing an aqueous phase were first saturated with EA. Then, an extra 500 microL of EA was added to extract the samples. Sample injection in CE could be made in hydrodynamic mode by dipping the injection end of the capillary into the organic (EA) phase in the volumetric flasks. As a demonstration, alkylphenones in water samples were extracted by LLsME into EA and subjected to separation by micellar electrokinetic chromatography (MEKC). Alkylphenones of C8-C12 with concentrations of about 10 ppb can be concentrated and detected after extraction; extraction efficiencies range from 72- to 334-fold. Linearity of extraction was determined and the effect on reproducibility by spiking an internal standard was studied. The method developed is time-saving and requires no further special experimental device other than a basic CE setup. Therefore, it would be readily acceptable for routine analysis, especially in analytical laboratories dealing with environmental samples.

Acetates↗

PubMed2000

Derivatization, extraction and concentration of amino acids and peptides by using organic/aqueous phases in capillary electrophoresis with fluorescence detection.

We report a novel method that facilitates sample pretreatment and detection in amino acid analysis by coupling solvent extraction with capillary electrophoresis. Amino acids and peptides were fluorescently labeled, concentrated into an organic solvent, and then separated by capillary zone electrophoresis with fluorescence detection. To achieve this, acetophenone was first employed to dissolve the derivatizing reagent, fluorescamine. The products, which possessed both hydrophilic and hydrophobic moieties, could be extracted and concentrated into the organic phase by suppressing the deprotonation of carboxyl groups, thus enhancing the hydrophobicity of the resulting molecules through pH modification in the aqueous solution. Furthermore, by fine-tuning the pH value, individual amino acids and short peptide molecules could be separated selectively from the sample bulk. This convenient, chemically controllable concentration technique may be useful in sample concentration and purification of biologically related samples such as amino acids and short peptides.

Amino Acids↗

PubMed2000

Stem cell factor (SCF) can regulate the activation and expansion of murine intraepithelial lymphocytes.

Murine intraepithelial lymphocytes (IEL) express c-kit, the receptor for stem cell factor (SCF). SCF induced a low but significant proliferative response in IEL, but not in splenic T cells. SCF stimulation of IEL resulted in an expansion of the c-kit(+), TCRgammadelta(+)cell population. SCF-induced proliferation was dependent upon SCF-c-kit interactions, since antibody to c-kit blocked this response, and IEL obtained from c-kit mutant (W/W(v)) mice failed to respond to SCF. SCF acted synergistically with anti-TCRgammadelta and with concavalin A (Con A) to induce proliferation and interferon gamma (IFN-gamma) production in IEL. Finally, mice injected with SCF had a significant increase in the number of IEL in the small intestine. SCF-treated mice had increased numbers of TCRalphabeta(+)and TCRgammadelta(+)cell populations, as well as increased numbers of c-kit(+)and c-kit(-)IEL. These data suggest that SCF-c-kit interactions play an important role in regulating IEL expansion and activation.

Animals↗

PubMed2000

New members of the parathyroid hormone/parathyroid hormone receptor family: the parathyroid hormone 2 receptor and tuberoinfundibular peptide of 39 residues.

The parathyroid hormone (PTH) family currently includes three peptides and three receptors. PTH regulates calcium homeostasis through bone and kidney PTH1 receptors. PTH-related peptide, probably also through PTH1 receptors, regulates skeletal, pancreatic, epidermal, and mammary gland differentiation and bladder and vascular smooth muscle relaxation and has a CNS role that is under investigation. Tuberoinfundibular peptide of 39 residues (TIP39) was recently purified from bovine hypothalamus based on selective PTH2 receptor activation. PTH2 receptor expression is greatest in the CNS, where it is concentrated in limbic, hypothalamic, and sensory areas, especially hypothalamic periventricular neurons, nerve terminals in the median eminence, superficial layers of the spinal cord dorsal horn, and the caudal part of the sensory trigeminal nucleus. It is also present in a number of endocrine cells. Thus TIP39 and PTH2 receptor-influenced functions may range from pituitary and pancreatic hormone release to pain perception. A third PTH-recognizing receptor has been found in zebrafish.

Amino Acid Sequence↗

PubMed2000

Study on angiogenesis factor of human osteosarcoma.

Angiogenesis factor of human osteosarcoma was partially purified and its biological features were studied. The active peptide with 8000 to 10,000 u molecular weight in the conditioned medium obtained from the cultivation of human osteosarcoma cells were partially purified by ultrafiltration, chromatography and dialysis. The angiogenic effects of the fractions were assessed by proliferation assay of human umbilical vein and pig aorta thoracic endothelial cells. The results showed that the chromatography fractions of 4 to 6 could significantly promote the proliferation of the endothelial cells. It was suggested that the human osteosarcoma cells could synthesize and secrete angiogenesis factor with a molecular weight of 8000 to 10,000 u.

Angiogenesis Inducing Agents↗

PubMed2000

Bovine calcined bone for the repair of radial defect in a rabbit model.

In order to investigate the bovine calcined bone's ability of repairing segmental bone defect and seek a new artificial bone substitute material, the bovine calcined bone (450 degrees C, 32 h) was implanted into the 10-mm middle radial defect of rabbits with tricalcium phosphate ceramics as the control. By using the methods of histology, radiology and biomechanics their osteogenic ability were measured. It was found that the bovine calcined bone's ability of repairing bone defect was better than that of tricalcium phosphate ceramics. The histological Nilsson's scores at 3rd, 5th, 9th week after operation were significantly increased (P < 0.01). At 12th week after operation the bending strength of radius in experimental group was much higher than that of control group and turned normal. It was suggested that bovine calcined bone is an ideal artificial bone substitute material with good ability of repairing segmental bone defect and some degree of mechanical strength.

Animals↗

PubMed2000

Mechanism of quinolone resistance in Staphylococcus aureus.

The resistance mechanisms to fluoroquinolones in Staphylococcus aureus were clarified by analyzing mutations in the genes encoding target enzymes, and examining the expression of the efflux pump, and determining the inhibitory activities of fluoroquinolones against the altered enzymes. Mutations in the grlA and gyrA genes of 344 clinical strains of S. aureus isolated in 1994 in Japan were identified by combinations of methods - single-strand conformation polymorphism analysis, restriction fragment length analysis, and direct sequencing - to identify possible relationships with fluoroquinolone resistance. Five types of single-point mutations and four types of double mutations were observed in the grlA gene in 204 strains (59.3%). Four types of single-point mutations and four types of double mutations were found in the gyrA gene in 188 strains (54.7%). Among these mutations, the grlA mutation of TCC --> TTC or TAC (Ser-80 --> Phe or Tyr) and the gyrA mutation of TCA --> TTA (Ser-84 --> Leu) were the principal ones, being detected in 137 (39.8%) and 121 (35.2%) isolates, respectively. A total of 15 types of mutation combinations within both genes were related to ciprofloxacin resistance (MIC greater than or equal 3.13 microg/ml) and were present in 193 mutants (56.1%). Strains containing mutations in both genes were highly resistant to ciprofloxacin (MIC50 =50 microg/ml). Those strains with the Ser-80 --> Phe or Tyr alteration in grlA, but wild type in gyrA showed a lower level of ciprofloxacin resistance (MIC50 less than or equal 12.5 microg/ml). Levofloxacin was active against 68 of 193 isolates (35.2%) with mutations at codon 80 of grlA in the presence or absence of concomitant mutations at codons 73, 84, or 88 in gyrA (MIC less than or equal 6.25 microg/ml). Sitafloxacin (DU-6859a) showed good activity in 186 of 193 isolates (96.4%), with an MIC of less than or equal 6.25 microg/ml. The contribution of membrane-associated multidrug efflux protein (NorA) expression to fluoroquinolone resistance was clarified by the checker-board titration method for determining the MIC of norfloxacin alone and in combination with carbonyl cyanide m-chlorophenylhydrazone. Among 344 clinical isolates, 139 strains (40.4%), in which the MIC of norfloxacin varied from 1.56 to >800 microg/ml, overexpressed the NorA protein. GrlA and GrlB proteins of topoisomerase IV, and GyrA and GyrB proteins of DNA gyrase encoded by genes with or without mutations were purified separately. The inhibitory activities of fluoroquinolones against the topoisomerase IV which contained a single amino acid change (Ser --> Phe at codon 80, Glu --> Lys at codon 84 of grlA, and Asp --> Asn at codon 432 of grlB) were from 5 to 95 times weaker than the inhibitory activities against the non-altered enzyme. These results suggest that the mutations in the corresponding genes may confer quinolone resistance; the active efflux pump, NorA, was considered to be the third quinolone-resistance mechanism. The numerous and complicated mutations seen may explain the rapid and widespread development of quinolone resistance described in S. aureus. Sitafloxacin showed good antibacterial activity against ciprofloxacin- or levofloxacin-resistant mutants because of its high inhibitory activity against both topoisomerase IV and DNA gyrase.

DNA Topoisomerase IV↗

PubMed2000

The role of cardioplegia induction temperature and amino acid enrichment in neonatal myocardial protection.

BACKGROUND: Warm cardioplegic induction improves the ischemically "stressed" adult heart. However, it is rarely used in infants, despite the fact that many newborn hearts are stressed by other factors such as hypoxia. The need for amino acids as well as their mechanism of action has also not been studied. METHODS: We first assessed the role of cardioplegic induction temperature in 10 nonhypoxic neonatal piglets undergoing 70 minutes of multidose blood cardioplegic arrest. Five piglets (group 1) received a cold (4 degrees C) induction, and 5 (group 2) a warm (37 degrees C) induction. Twenty-six other piglets underwent ventilator hypoxia (fraction of inspired oxygen, 8% to 10%) for 60 minutes before cardiopulmonary bypass (stress). Six piglets (group 3) then underwent 70 minutes of cardiopulmonary bypass without ischemia (hypoxia controls), and 20 underwent 70 minutes of cardioplegic arrest. Five of these (group 4) received cold cardioplegic induction, and 15 received warm induction; in 5 of these (group 5), the warm cardioplegic solution contained amino acids, in 5 others (group 6), it was unsupplemented, and in the remaining 5 (group 7), nitroglycerin was added to determine the role of vasodilation. Myocardial function was assessed by pressure-volume loops (expressed as a percent of control), and coronary vascular resistance was measured with cardioplegic infusions. RESULTS: In nonhypoxic (normal) piglets, cold (group 1) and warm (group 2) induction completely preserved systolic function (end-systolic elastance, 100% versus 104%) and preload recruitable stroke work (100% versus 102%), with minimal increase in diastolic compliance (162% versus 156%). Hypoxia-reoxygenation alone (group 3) depressed systolic function (end-systolic elastance, 51%+/-2%) and preload recruitable stroke work (54%+/-3%), and raised diastolic stiffness (260%+/-15%). The detrimental effects of reoxygenation persisted (unchanged from reoxygenation alone) with cold induction (group 4) or warm induction without amino acids (groups 6 and 7). In contrast, warm induction with amino acids (group 5) restored systolic function (end-systolic elastance, 105%+/-3%; p < 0.001 versus groups 3, 4, 6, and 7) and preload recruitable stroke work (103%+/-2%; p < 0.001 versus groups 3, 4, 6, and 7), and decreased diastolic stiffness (154%+/-7%; p < 0.001 versus groups 3, 4, 6, and 7). However, there was no difference in myocardial oxygen consumption in hypoxic hearts receiving a warm induction (6.9 versus 6.5 versus 7.3 mL/g per 5 minutes) (groups 5, 6, 7), and coronary vascular resistance was lowest with nitroglycerin (group 7). CONCLUSIONS: Cardioplegic induction can be given either warm or cold in nonhypoxic neonatal hearts. In contrast, only warm induction with amino acids repairs the hypoxic injury, but the primary mechanism of action is not related to increased metabolic activity or vasodilation.

Adenosine↗

PubMed2000

Reducing postischemic reperfusion damage in neonates using a terminal warm substrate-enriched blood cardioplegic reperfusate.

BACKGROUND: In adult cardiac operations, a warm cardioplegic reperfusate ("hot shot") before removing the aortic cross-clamp improves postbypass myocardial function and metabolic recovery. This modality, however, is rarely used in infants, despite the fact that postbypass cardiac dysfunction remains problematic, especially in cyanotic ("stressed") patients. METHODS: To produce stress, 15 neonatal piglets underwent 60 minutes of ventilator hypoxia (fraction of inspired oxygen, 8% to 10%). All piglets then received similar protection with multidose cold blood cardioplegic solution during 70 minutes of arrest and were separated into three groups to examine the role of a warm reperfusate as well as possible augmentation by aspartate and glutamate enrichment. In 5 piglets (group 1), the cross-clamp was simply removed; in 5 (group 2), an unsupplemented warm blood cardioplegic reperfusate was given; and in 5 (group 3), the warm reperfusate was enriched with aspartate and glutamate. Myocardial function was assessed using pressure-volume loops and expressed as a percentage of control. RESULTS: Compared with hearts receiving reperfusion with unmodified blood (group 1), a warm unsupplemented cardioplegic reperfusate (group 2) slightly improved systolic contractility (end-systolic elastance, 41% versus 50%; p < 0.05 versus group 1) and preload recruitable stroke work (41% versus 52%; p < 0.05 versus group 1), reduced diastolic stiffness (263% versus 245%; p < 0.05 versus group 1), and increased adenosine triphosphate (10.7 versus 11.9 microg/g tissue, p < 0.05 versus group 1). However, if aspartate and glutamate was included in the warm reperfusate (group 3), there was complete recovery of systolic function (end-systolic elastance, 105%+/-3%; p < 0.001 versus all groups) and preload recruitable stroke work (103%+/-2%; p < 0.001 versus all groups), a minimal rise in diastolic stiffness (154%+/-7%; p < 0.001 versus all groups), and preservation of adenosine triphosphate (15.5+/-0.5 microg/g; p < 0.001 versus all groups). CONCLUSIONS: A warm cardioplegic reperfusate helps reduce the reperfusion injury, resulting in improved myocardial function and metabolic recovery in hypoxic (stressed) neonatal hearts, and this effect is maximized if the reperfusate is enriched with aspartate and glutamate, which completely preserves myocardial function.

Adenosine Triphosphate↗

PubMed2000

Lowering reperfusion pressure reduces the injury after pulmonary ischemia.

BACKGROUND: Controlled reperfusion with a modified solution limits pulmonary injury following ischemia. Our initial studies infused this modified reperfusate at a pressure of 40 to 50 mm Hg to insure distribution. However, perhaps a lower pressure, which is closer to the normal physiologic pressure in the lung, would improve results by decreasing sheer stress. METHODS: Fifteen adult pigs underwent 2 hours of lung ischemia by clamping the left bronchus and pulmonary artery. Five (group 1) then underwent uncontrolled reperfusion by removing the vascular clamps and allowing unmodified blood to reperfuse the lung at a pulmonary artery pressure of 20 to 30 mm Hg. The other 10 pigs underwent controlled reperfusion by mixing blood from the femoral artery with a crystalloid solution, and infusing this modified reperfusate into the ischemic lung through the pulmonary artery for 10 minutes before removing the arterial clamp. In 5 (group 2), the modified solution was infused at a pressure of 40 to 50 mm Hg, and in 5 (group 3) 20 to 30 mm Hg. Lung function was assessed 60 minutes after reperfusion and expressed as percentage of control. RESULTS: Compared to uncontrolled reperfusion (group 1), controlled reperfusion at a pressure of 40 to 50 mm Hg (group 2) significantly improved postreperfusion pulmonary compliance (77% versus 86%; p<0.001 versus group 1), and arterial/alveolar ratio (a/A) ratio (27% versus 52%; p<0.001 versus group 1); as well as decreased pulmonary vascular resistance (PVR) (198% versus 154%; p<0.001 versus group 1), lung water (84.3% versus 83.5%; p<0.001 versus group 1), and myeloperoxidase (0.35 versus 0.23 optical density/min/mg protein). Reducing the pressure of the modified reperfusate to 20 to 30 mm Hg further improved postreperfusion compliance (92%+/-1%; p<0.001 versus groups 1 and 2) and a/A ratio (76%+/-1%; p<0.001 versus groups 1 and 2); and lowered PVR (133%+/-2%; p<0.001 versus groups 1 and 2), lung water (82.7%+/-0.1%; p<0.001 versus groups 1 and 2), and myeloperoxidase (0.16%+/-0.01%; p<0.001 versus groups 1 and 2). CONCLUSIONS: After 2 hours of pulmonary ischemia, a severe lung injury occurs following uncontrolled reperfusion, controlled reperfusion with a modified solution reduces this reperfusion injury, and lowering the pressure of the modified reperfusate to more physiologic levels (20 to 30 mm Hg) further reduces the reperfusion injury improving pulmonary function.

Animals↗

PubMed2000

Distribution of parathyroid hormone-2 receptor-like immunoreactivity and messenger RNA in the rat nervous system.

The parathyroid hormone-2 receptor is a member of the secretin family of guanine nucleotide-binding protein-coupled receptors. The human parathyroid hormone-2 receptor is activated by parathyroid hormone and a recently purified hypothalamic polypeptide, tubero-infundibular peptide of 39 residues, while the rat parathyroid hormone-2 receptor is poorly activated by parathyroid hormone and is potently activated by tubero-infundibular peptide of 39 residues. In order to provide a foundation for studies on the physiological role of the parathyroid hormone-2 receptor and tubero-infundibular peptide of 39 residues, we investigated the cellular distribution of the parathyroid hormone-2 receptor in the rat CNS using both immunohistochemistry and in situ hybridization histochemistry. The receptor is found in discrete groups of neurons in many regions. It is present in scattered small cells throughout the cerebral cortex, in small and medium-sized cells in the striatum, and is quite abundant in the septum and the midline thalamic nuclei. Its expression is high in the hypothalamus, particularly in the periventricular and arcuate nuclei. Fibers and terminals in the external zone of the median eminence, and in the superficial layers of the caudal spinal trigeminal tract and the spinal cord dorsal horn, are strongly and dramatically labeled by a parathyroid hormone-2 receptor-selective antibody. The localization of parathyroid hormone-2 receptor suggests a role in the regulation of pituitary hormone secretion, sensory information processing and homeostatic regulation.

Animals↗

PubMed2000

A multi-element ICP-MS survey method as an alternative to the heavy metals limit test for pharmaceutical materials.

A multi-element inductively coupled plasma-mass spectrometry (ICP-MS) survey method has been demonstrated as an alternative to the antiquated 'heavy metals limit test' prescribed by United States Pharmacopoeia (USP), European Pharmacopoeia (EP), and British Pharmacopoeia (BP), for drug substances, intermediates, and raw materials. The survey method is simple, fast, sensitive, semi-quantitative to quantitative, and includes all the elements which can be analyzed by atomic spectroscopy.

Calibration↗

PubMed2000

Syntheses and biological activity of C-3'-difluoromethyl-taxoids.

A series of new taxoids bearing difluoromethyl group at the C-3' position and modifications at the C-10 and C-14 positions has been synthesized and their biological activities studied. The in vitro cytotoxicity assay results indicate that these newly developed taxoids exhibit comparable to several times better activity against drug-sensitive cell line LCC6-WT, and 40-70 times better activity against the corresponding drug-resistant cancer cell line LCC6-MDR as compared to that of paclitaxel. Apoptosis analysis has revealed the exceptional activity of SB-T-12843 (1e) in inducing apoptosis in both MDR-bearing and MDR-negative cancer cells.

Antineoplastic Agents, Phytogenic↗

PubMed2000

Synthesis and evaluation of 6-[(18)F]fluoro-3-(2(S)-azetidinylmethoxy)pyridine as a PET tracer for nicotinic acetylcholine receptors.

Both ABT-594 ((R)-2-chloro-5-(2-azetidinylmethoxy)pyridine) and A-85380 (3-[2(S)-2-azetidinylmethoxy]pyridine), novel nicotinic agonists that possess potent non-opioid analgesic properties, have high affinity for neuronal nicotinic acetylcholine receptors (nAChR) but do not elicit the pronounced toxicity of epibatidine. 6-[(18)F]Fluoro-3-(2(S)-azetidinylmethoxy)pyridine (6-[(18)F]fluoro-A-85380), a F-18 labeled analogue of these two compounds, is therefore a promising radioligand for positron emission tomography (PET) studies in humans. The use of trimethylammonium as a leaving group in nucleophilic aromatic substitution reactions has proven to be a versatile and efficient strategy, and offers several advantages over other leaving groups. Here, we report the synthetic strategy for the preparation of a precursor, as a trimethylammonium iodide salt, and its use in the radiosynthesis to 6-[(18)F]fluoro-A-85380. Preliminary compartative PET studies of 6-[(18)F]fluoro-A-85380 and 2-[(18)F]fluoro-A-85380 were carried out in baboon to examine their suitability as tracers for studying nAChR system.

Animals↗

PubMed2000

Red blood cells from the South American rattlesnake (Crotalus durissus terrificus) regulate volume incompletely following osmotic shrinkage and swelling in vitro.

The ability of rattlesnake (Crotalus durissus terrificus) red blood cells to volume regulate in vitro has been investigated. Blood was drawn through a catheter inserted in the dorsal aorta and equilibrated to gas mixtures of different composition. Cells shrunken osmotically by increasing the extracellular osmolarity from approximately 291 mosm l(-1) (n=3) to approximately 632 mosm l(-1) (calculated) only partially regulated their volume back towards the original volume either at pH 7.51+/-0.05 (mean+/-S.D., n=5) or pH 7. 20+/-0.06 (mean+/-S.D., n=3). There was no improvement of the regulatory volume increase at low haemoglobin oxygen saturation. The limited volume restoration was inhibited by separate additions of amiloride (10(-4) M) or DIDS (10(-4) M) suggesting involvement of the Na(+)/H(+) and Cl(-)/HCO(3)(-) exchangers. Cells that were swollen osmotically by an approximately 30% dilution of the extracellular medium also exhibited a limited ability to recover their volume. Therefore, these cells show little ability to volume regulate when exposed to in vitro conditions that shrink or swell the cell.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed2000

Ghost cells in calcifying odontogenic cyst express enamel-related proteins.

The so-called ghost cell is a unique cell type occurring in a variety of odontogenic and non-odontogenic lesions. However, the true nature of ghost cells has not been determined. In the present study, we examined the immunoreactivity of ghost cells in calcifying odontogenic cysts and dermal calcifying epitheliomas, with antibodies against amelogenin, enamelin, sheath protein (sheathlin) and enamelysin, in an attempt to clarify the nature of this unique cell. The cytoplasm of ghost cells in calcifying odontogenic cysts demonstrated distinct immunolocalization of the enamel-related proteins, while similar in the calcifying epitheliomas of the skin showed a negative reaction. The results indicate that the ghost cells in calcifying odontogenic cysts, as opposed to ghost cells in dermal calcifying epitheliomas, contain enamel-related proteins in their cytoplasm accumulated during the process of pathological transformation.

Amelogenin↗

PubMed2000

One-step sandwich enzyme immunoassay using monoclonal antibodies for detection of human enamelysin (MMP-20).

A one-step sandwich enzyme immunoassay (EIA) system for human matrix metalloproteinase 20 (MMP-20, enamelysin) was established by use of a solid-phase monoclonal antibody and a separate peroxidase-labeled monoclonal antibody. The EIA system was shown to be sensitive and quantitative for the detection of MMP-20. As little as 1.0 ng/ml (50 pg/assay) of MMP-20 protein could be reliably detected. The EIA system was linear over a range of 2.5-160 ng/ml (125-8,000 pg/assay), and the EIA system was versatile in that it was capable of detecting with equal sensitivity proMMP-20, active MMP-20, and MMP-20 with COOH-terminal deletions. The EIA system was validated by the successful detection of MMP-20 in the culture medium of Chinese hamster ovary cells (CHO-K1) that were transfected with an MMP-20 expression vector. No MMP-20 was detected in normal human serum, normal saliva, or in selected tumors. However, when recombinant human MMP-20 was added to human saliva, the EIA system did detect quantifiable amounts of the MMP-20, indicating that the system will work within the framework of complex in biological fluids.

Adenocarcinoma↗

PubMed2000

Time-of-day effects on response of natural killer cells to acute stress in men and women.

Diurnal influences on natural killer (NK) cell changes to acute stress were assessed in 21 men and 21 women assigned to either an acute stress (mental arithmetic) or control task condition. Sessions began at either 8 a.m. or 2 p.m. Number of NK (CD3-CD56+) cells and NK activity were measured at baseline, during the 5-min task, and 60 and 90 min after the task. Both morning and afternoon stress participants had elevated NK cell numbers during the task. After the task, number of NK cells decreased in morning stress participants but remained significantly above baseline levels 60 and 90 min posttask. NK cell numbers in afternoon stress participants decreased to below baseline levels 60 and 90 min after the task. Changes in NK activity were driven primarily by diurnal influences. NK activity increased in all morning participants and stayed increased 60 and 90 min posttask. NK activity of all afternoon participants also increased during the task but dropped below baseline 60 and 90 min later. Greater increases in NK levels and activity during the task were associated with greater heart rate changes.

Adolescent↗