Microplastic (MP) has become ubiquitous in the marine environment. Its threat to marine organisms has been demonstrated under laboratory conditions, yet studies on wild populations still face ...methodological difficulties. We reviewed the methods used to separate MP from soft animal tissues and highlighted a lack of standardised methodologies, particularly critical for synthetic microfibres. We further compared enzymatic and a potassium hydroxide (KOH)-based alkaline digestion protocols on wild crabs (Carcinus aestuarii) collected from three coastal lagoons in the north Adriatic Sea and on laboratory-prepared synthetic polyester (PES) of different colour and polypropylene (PP). We compared the cost-effectiveness of the two methods, together with the potential for adverse quantitative or qualitative effects on MP that could alter the capability of the polymers to be recognised via microscopic or spectroscopic techniques. Only 5.5% of the 180 examined crabs contained MP in their gastrointestinal tracts, with a notably high quantitative variability between individuals (from 1 to 117 particles per individual). All MP found was exclusively microfibres, mainly PES, with a mean length (±SE) of 0.5 ± 0.03 mm. The two digestion methods provided comparable estimates on wild crabs and did not cause any visible physical or chemical alterations on laboratory-prepared microfibres treated for up to 4 days. KOH solution was faster and cheaper compared to the enzymatic extraction, involving fewer procedural steps and therefore reducing the risk of airborne contamination. With digestion times longer than 4 days, KOH caused morphological alterations of some of the PES microfibres, which did not occur with the enzymatic digestion. This suggests that KOH is effective for the digestion of small marine invertebrates or biological samples for which shorter digestion time is required, while enzymatic extraction should be considered as alternative for larger organisms or sample sizes requiring longer digestion times.
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•It is fundamental to identify cost-effective methods to separate MP from biota.•The effects of the digestion treatments on plastic microfibres were evaluated.•Extensive contamination and plastic overestimation controls were implemented.•Crabs contained very variable quantitative of synthetic particles (from 0 to 117).•Digestion with KOH is the most cost-effective procedure for the extraction of MP.
Only 5.5% of crabs contained microplastic in their gastrointestinal tracts, with a high quantitative variability between individuals. Enzymatic and KOH digestion methods did not cause any visible alterations of microfibres.
1 Aging Study Unit, Geriatric
Research, Education, and Clinical Center, Veterans Affairs Health Care
System, and Division of Gerontology, Endocrinology, and Metabolism,
Stanford University Medical ...School, Palo Alto, California 93404;
2 Thermal and Mountain Division,
US Army Research Institute of Environmental Medicine, Natick,
Massachusetts 01760; 3 Department
of Integrative Biology, University of California, Berkeley, California
94720; 4 Womens Health Research
Center, University of Colorado, Denver 80262; and
5 Department of Kinesiology and
Applied Physiology, University of Colorado, Boulder, Colorado 80309
To evaluate the hypothesis that
exposure to high altitude would reduce blood glucose and total
carbohydrate utilization relative to sea level (SL), 16 young women
were studied over four 12-day periods: at 50% of peak
O 2 consumption in different
menstrual cycle phases (SL-50), at 65% of peak
O 2 consumption at SL (SL-65), and
at 4,300 m (HA). After 10 days in each condition, blood glucose rate of
disappearance (R d ) and
respiratory exchange ratio were measured at rest and during 45 min of
exercise. Glucose R d during exercise at HA (4.71 ± 0.30 mg · kg 1 · min 1 )
was not different from SL exercise at the same absolute intensity (SL-50 = 5.03 mg · kg 1 · min 1 )
but was lower at the same relative intensity (SL-65 = 6.22 mg · kg 1 · min 1 ,
P < 0.01). There were no
differences, however, when glucose R d was corrected for energy
expended (kcal/min) during exercise. Respiratory exchange ratios
followed the same pattern, except carbohydrate oxidation remained lower
( 23.2%, P < 0.01) at HA than
at SL when corrected for energy expended. In women, unlike in men,
carbohydrate utilization decreased at HA. Relative abundance of
estrogen and progesterone in women may partially explain the sex
differences in fuel utilization at HA, but subtle differences between
menstrual cycle phases at SL had no physiologically relevant effects.
stable isotope; hypobaric hypoxia; substrate utilization; glucose
flux; gender differences; ovarian hormones; menstrual cycle
E. E. Wolfel, M. A. Selland, R. S. Mazzeo and J. T. Reeves
Cardiovascular Pulmonary Research Laboratory, University of Colorado Health Sciences Center, Denver 80262.
Residence at high altitude has ...been associated with elevation in systemic
arterial blood pressure, but the time course has been little studied and
the mechanism is unknown. Because plasma epinephrine (E) and norepinephrine
(NE) also increase at altitude, we hypothesized that heightened
sympathoadrenal activity may cause increased arterial pressure. We measured
ambulatory blood pressure by cuff monitor in relation to 24-h urinary
excretion of E and NE at sea level and during 3 wk of residence at 4,300 m
(Pikes Peak, CO) in 11 healthy men. In five subjects taking placebo,
arterial pressure progressively increased at 4,300 m from 82 +/- 1 (SE)
mmHg at sea level to 88 +/- 3 on day 2, 91 +/- 3 on day 8, and 97 +/- 6 on
day 17. In six subjects, propranolol (240 mg/day) decreased pressure from
85 +/- 4 to 77 +/- 1 mmHg at sea level but did not prevent sustained
increase in pressure at 4,300 m (84 +/- 1, 81 +/- 1, and 85 +/- 3 mmHg on
days 2, 8, and 17, respectively). Compared with the placebo group, blood
pressure did not increase further over the initial elevation observed on
day 2 in the propranolol group. There was interindividual variability in
the blood pressure responses in both groups, with some subjects
demonstrating a more marked increase in blood pressure. Urinary excretion
of NE increased concomitantly with pressure at altitude in both groups,
with a greater rise in the placebo group.
In carotid endarterectomy (CEA), EEG and somatosensory evoked potentials (SEPs) are the most commonly used monitoring techniques to prevent perioperative stroke. However, which of these methods is ...the most appropriate is not definitely established. Here we evaluated retrospectively simultaneous EEG and SEP recordings. Our CEA series was analyzed backward to identify 30 patients requiring carotid shunt. Shunting was performed in 7.1% of 420 consecutive CEA over a 20-month period. All CEAs were continuously monitored by multi-channel EEG and SEPs before, during and 20 min following carotid cross-clamping. The most reliable SEP criterion for shunting was marked amplitude reduction or disappearance of cortical components (N20, P25), usually associated or preceded by a unilateral or bilateral suppression of EEG activity. Three of the shunted patients had minor postoperative neurological deficits. Amongst the 390 non-shunted patients, 1 had a postoperative ischemic stroke and 1 one had a cerebral hemorrhage. Findings confirm that SEPs are less sensitive but more specific than EEG for the detection of cerebral ischemia in CEA. The number of shunting and major ischemic events in non-shunted patients associated to simultaneous EEG and SEP monitoring was lower than those commonly reported in the literature of CEA.
1 Department of Kinesiology and Applied Physiology,
University of Colorado, Boulder, Colorado 80309; and
2 Department of Physiology and Biophysics, Case Western
Reserve University, Cleveland, Ohio ...44106
The purpose of this study was to
examine the effect of acute (24 h) and chronic (5 wk) hypobaric hypoxic
exposure equivalent to a simulated altitude of 4,300 m (446 mmHg) on
the enzymes of fat metabolism. Heart, liver, and skeletal muscle were
taken from 32 male Sprague-Dawley rats. Altitude exposure did not
affect the activity of citrate synthase in any of the tissues,
suggesting that mitochondrial content was unchanged. Carnitine
palmitoyltransferase-I (CPT-I) activity was significantly reduced in
the heart by both acute and chronic high altitude exposure compared
with controls. A similar reduction was found for CPT-I activity in
extensor digitorum longus after acute and chronic exposure
compared with control animals. CPT-I activity was not affected by
altitude exposure in the soleus muscle or the liver. 3-Hydroxyacyl-CoA
dehydrogenase ( -HAD) activity was significantly depressed in the
hearts of chronically exposed animals compared with controls. No
difference between acute and control animals was found in the heart for
-HAD activity. Liver -HAD activity was also significantly
decreased in the acclimatized as well as in the acute animals compared
with the control group. Quadriceps -HAD activity was reduced for the chronic animals only compared with controls. These data suggest that
acclimatization to high altitude selectively decreases key enzymes in
fat utilization and oxidation in the heart, liver, and select skeletal muscles.
hypobaric hypoxia; 3-hydroxyacyl-CoA dehydrogenase; carnitine
palmitoyltransferase-I
A. C. Roberts, J. T. Reeves, G. E. Butterfield, R. S. Mazzeo, J. R. Sutton, E. E. Wolfel and G. A. Brooks
University of California, Berkeley 94720, USA.
To test the hypothesis that altitude exposure ...increases glucose utilization
and that this increment is mediated by a beta-adrenergic mechanism, the
effects of hypobaric hypoxia and beta-blockade on glucose rates of
appearance (Ra), disappearance (Rd), oxidation (Rox), and leg uptake G =
2(arteriovenous glucose difference)(1 - leg blood flow) were measured
during rest and a given submaximal exercise task. We studied six healthy
beta-blocked (beta) men 26.7 +/- 1.2 (SE) yr, 74.0 +/- 6.6 kg and five
matched controls (C; 26 +/- 1.2 yr, 69.3 +/- 2.6 kg) in energy and nitrogen
balance during rest and leg cycle-ergometer exercise at sea level, on acute
altitude exposure to 4,300 m (barometric pressure = 463 Torr), and after 3
wk of habituation. Subjects received a primed continuous infusion of
6,6-2H- and 1-13Cglucose, rested for > or = 90 min, and then
immediately exercised for 45 min at 89 W, which elicited 49% of sea-level
peak O2 consumption (VO2peak; 65% of altitude VO2peak). At sea level,
resting Ra was 1.47 +/- 0.19 and 1.66 +/- 0.16 mg x kg-1 x min-1 for C and
beta, respectively, and increased to 3.04 +/- 0.25 and 3.56 +/- 0.27 mg x
kg-1 x min-1, respectively, during exercise. Thus glucose Ra was
significantly increased by beta-blockade during rest and exercise at sea
level. At sea level, beta-blockade increased leg G, which accounted for 49
and 69% of glucose disposal during exercise in C and beta, respectively. On
acute altitude exposure, glucose Ra rose significantly during rest and
exercise relative to sea level, whereas blockade continued to augment this
increment. During exercise on acute exposure, G increased more than at sea
level and accounted for a greater percentage (80 and 97%, respectively) of
Rd in C and beta during exercise. Similarly, Rox values, particularly
during exercise, were increased significantly at altitude relative to sea
level, and beta-blockade potentiated this effect. During a given submaximal
exercise task after acclimatization, glucose Ra, Rox, and G were increased
relative to sea level, but these increments were less than those in
response to exercise measured on acute exposure. We conclude that altitude
exposure increases glucose use during rest and a given submaximal exercise
bout and beta-blockade exaggerates the response.
R. S. Mazzeo and P. Marshall
Department of Kinesiology, University of Colorado, Boulder 80309.
This investigation examined the relationship among plasma catecholamines,
the blood lactate threshold ...(TLa), and the ventilatory threshold (TVE) in
highly trained endurance athletes. Six competitive cyclists and six varsity
cross-country runners performed a graded exercise test via two different
modalities: treadmill running and bicycle ergometry. Although maximal
oxygen consumption (VO2 max) did not differ significantly for the cyclists
for treadmill running and cycling (64.6 +/- 1.0 and 63.5 +/- 0.4 ml
O2.kg-1-min-1, respectively), both TLa and TVE occurred at a relatively
earlier work load during the treadmill run. The opposite was true for the
runners as TLa and TVE appeared at an earlier percent of VO2max during
cycling compared with treadmill running (60.0 +/- 1.7 vs. 75.0 +/- 4.0%,
respectively, TLa). The inflection in plasma epinephrine shifted in an
identical manner and occurred simultaneously with that of TLa (r = 0.97)
regardless of the testing protocol or training status. Although a high
correlation (r = 0.86) existed for the shift in TVE and TLa, this
relationship was not as strong as was seen with plasma epinephrine. The
results suggest that a causal relationship existed between the inflection
in plasma epinephrine and TLa during a graded exercise test. This
association was not as strong for TVE and TLa.
1 Department of Kinesiology and Applied Physiology,
University of Colorado, Boulder, Colorado 80309; 2 Palo Alto
Veterans Affairs Health Care System, Palo Alto, California 94304;
and 3 University ...of Colorado Health Sciences Center, Denver,
Colorado 80262
Interleukin-6
(IL-6), an important cytokine involved in a number of biological
processes, is consistently elevated during periods of stress. The
mechanisms responsible for the induction of IL-6 under these conditions
remain uncertain. This study examined the effect of -adrenergic
blockade on the IL-6 response to acute and chronic high-altitude
exposure in women both at rest and during exercise. Sixteen healthy,
eumenorrheic women (aged 23.2 ± 1.4 yr) participated in the
study. Subjects received either -adrenergic blockade (prazosin, 3 mg/day) or a placebo in a double-blinded, randomized fashion.
Subjects participated in submaximal exercise tests at sea level and on
days 1 and 12 at altitude (4,300 m). Resting
plasma and 24-h urine samples were collected throughout the duration of
the study. At sea level, no differences were found at rest for plasma
IL-6 between groups (1.5 ± 0.2 and 1.2 ± 0.3 pg/ml for
placebo and blocked groups, respectively). On acute ascent to altitude,
IL-6 levels increased significantly in both groups compared with
sea-level values (57 and 84% for placebo and blocked groups,
respectively). After 12 days of acclimatization, IL-6 levels remained
elevated for placebo subjects; however, they returned to sea-level
values in the blocked group. -Adrenergic blockade significantly
lowered the IL-6 response to exercise both at sea level (46%) and at
altitude (42%) compared with placebo. A significant correlation
( P = 0.004) between resting IL-6 and urinary
norepinephrine excretion rates was found over the course of time while
at altitude. In conclusion, the results indicate a role for
-adrenergic regulation of the IL-6 response to the stress of both
short-term moderate-intensity exercise and hypoxia.
hypoxia; catecholamines; norepinephrine; epinephrine; cytokines
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