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W Block

Publications and source records attributed to W Block.

At least 55 records · Page 3Linked to original sources
PubMed1998

Diagnostic value of a superparamagnetic iron oxide in MR imaging of chronic liver disease in an animal model.

OBJECTIVE: The enhancement characteristics and the diagnostic value of a cell-specific superparamagnetic contrast agent (NSR 0430) in different degrees of liver fibrosis and cirrhosis were experimentally studied in an animal model. MATERIALS AND METHODS: Chronic liver damage was induced in rats either by oral administration of carbon tetrachloride (CCl4) for 15 weeks (n = 37) or by oral administration of thioacetamide (TAA) in drinking water for 24-26 weeks (n = 48). Twenty-six animals served as control subjects. T1 and T2 relaxation times for the liver and the spleen were measured in vitro with a spectrometer at 40 MHz. In vivo MR imaging at 1.5 T also was performed using T2-weighted turbo spin-echo sequences before and 1 hr after administration of NSR 0430. All data were correlated with the histologic degree of liver fibrosis and cirrhosis and the amount of connective tissue in the liver, which was measured morphometrically. RESULT: CCl4 produced liver fibrosis in most of the animals, and TAA predominantly caused liver cirrhosis. NSR 0430 caused a T2 relaxation time decrease in the control animals by 49%; in the CCl4 group with light and moderate liver fibrosis, by 25%; in the CCl4 group with severe liver fibrosis or cirrhosis, by 16%; and in the TAA group with cirrhosis, by 30%. On the T2-weighted turbo spin-echo sequences, liver signal-to-noise ratios (SNRs) decreased after contrast agent administration in the control animals by 81% and 79%, depending on the TE parameter. In the CCl4 group, liver SNRs decreased by 96% and 61% in animals with light or moderate fibrosis and by 44% and 55% in animals with severe fibrosis or cirrhosis, depending on the TE parameter. In the TAA group, liver SNR decreased by 61% and 67%, depending on the TE parameter. CONCLUSION: Enhancement of the superparamagnetic contrast agent NSR 0430 is decreased in the presence of liver fibrosis and cirrhosis in an animal model. However, the reduced enhancement is not directly related to the degree of chronic liver damage, which limits the diagnostic value of superparamagnetic contrast agents in the assessment of chronic liver disease.

Animals↗
PubMed1997

Effect of cytochrome P450 induction on phosphorus metabolites and proton relaxation times measured by in vivo 31P-magnetic resonance spectroscopy and 1H-magnetic resonance relaxometry in human liver.

Experimental and clinical studies have led to the hypothesis that the phosphodiester signal obtained by 31P magnetic resonance (MR) spectroscopy may be a specific marker for the hepatic induction of oxidative metabolism (P450 induction) by phenobarbitone or ethanol. Systematic studies in humans are lacking. Therefore, we studied 10 volunteers who received rifampin (600 mg/d) for 6 days, resulting in a documented induction of oxidative metabolism as measured by an increase in urinary 6-beta-hydroxycortisol output in all volunteers (P = .0004). 31P-MR spectroscopy and 1H-MR relaxometry were performed before and after hepatic P450 induction. As shown by 31P-MR spectroscopy, the median phosphomonoester concentration (PME) relative to nucleoside triphosphate (NTP) increased by 21% from 0.63 (range, 0.40-0.89) before induction to 0.76 (0.49-1.67) after induction (P = .0451). The median level of phosphodiesters (PDE) relative to NTP increased by 28% from 4.82 (3.41-6.67) before induction to 6.18 (4.63-11.63) after induction (P = .0091). An increase in the level of inorganic phosphates (Pi) relative to NTP was observed, but changes were not significant. As shown by 1H-MR relaxometry, a nonsignificant trend of the liver parenchyma to shorter relaxation times was observed after P-450 induction. In conclusion, both PME/NTP and PDE/NTP ratios (measured by in vivo 31P-MR spectroscopy) increased significantly after hepatic induction with rifampin. Further clinical studies with 31P-MR spectroscopy must take into account the potential effects of P450-inducing agents.

Adult↗
PubMed1997

RARE spiral T2-weighted imaging.

Spiral imaging has a number of advantages for fast imaging, including an efficient use of gradient hardware. However, inhomogeneity -induced blurring is proportional to the data acquisition duration. In this paper, we combine spiral data acquisition with a RARE echo train. This allows a long data acquisition interval per excitation, while limiting the effects of inhomogeneity. Long spiral k-space trajectories are partitioned into smaller, annular ring trajectories. Each of these annular rings is acquired during echoes of a RARE echo train. The RARE refocusing RF pulses periodically refocus off-resonant spins while building a long data acquisition. We describe both T2-weighted single excitation and interleaved RARE spiral sequences. A typical sequence acquires a complete data set in three excitations (32 cm FOV, 192 x 192 matrix). At a TR = 2000 ms, we can average two acquisitions in an easy breath-hold interval. A multifrequency reconstruction algorithm minimizes the effects of any off-resonant spins. Though this algorithm needs a field map, we demonstrate how signal averaging can provide the necessary phase data while increasing SNR. The field map creation causes no scan time penalty and essentially no loss in SNR efficiency. Multiple slice, 14-s breath-hold scans acquired on a conventional gradient system demonstrate the performance.

Abdomen↗
PubMed1997

Consistent fat suppression with compensated spectral-spatial pulses.

Reliable fat suppression is especially important with fast imaging techniques such as echo-planar (EPI), spiral, and fast spin-echo (FSE) T2-weighted imaging. Spectral-spatial excitation has a number of advantages over spectrally selective presaturation techniques, including better resilience to B0 and B1 inhomogeneity. In this paper, a FSE sequence using a spectral-spatial excitation pulse for superior fat suppression is presented. Previous problems maintaining the CPMG condition are solved using simple methods to accurately program radio-frequency (RF) phase. Next an analysis shows how B0 eddy currents can reduce fat suppression effectiveness for spectral-spatial pulses designed for conventional gradient systems. Three methods to compensate for the degradation are provided. Both the causes of the degradation and the compensation techniques apply equally to gradient-recalled applications using these pulses. These problems do not apply to pulses designed for high-speed gradient systems. The spectral-spatial FSE sequence delivers clinically lower fat signal with better uniformity than spectrally selective pre-saturation techniques.

Adipose Tissue↗
PubMed1997

Temperature Regulation of Supercooling and Gut Nucleation in Relation to Diapause of Pyrrhocoris apterus (L.) (Heteroptera)

The heteropteran Pyrrhocoris apterus (L.) does not survive freezing of its body fluids; there is a good correlation between values of survival at subzero temperatures and the supercooling point (SCP), i.e., the temperature at which body fluids start to freeze. The decrease of the SCP and thus the increase in cold hardiness is regulated by photoperiod and temperature. The relative importance of these factors depends on the physiological state of the insect. The SCP is about -7°C at the onset of prediapause and a decrease of about 4-5°C is associated with the development of the diapause syndrome in adults; these processes both are induced by a short-day photoperiod with temperature playing a secondary role. The induction of the diapause syndrome is a prerequisite for the subsequent decrease of the SCP by about 5-6°C during cold acclimation. An intermediate temperature of 15°C, or fluctuating outdoor temperatures and short-day photoperiods, are more suitable for the decrease of SCP than 5°C in continuous darkness. The sensitivity to photoperiod gradually disappears during the development of diapause; after the termination of diapause around the winter solstice the SCP irreversibly increases at a high temperature of 26°C even if exposed to a short-day photoperiod. The SCPs of hemolymph, gut, fat body, and gonads were compared to whole-body SCP. The gut was identified as the primary site of ice nucleation because its SCP value was very similar to the value for the whole body in both short-day and long-day insects. The SCPs of other organs, including the hemolymph, were always lower than the whole body SCP. Food was not a source of ice nucleating agents because the SCP of freshly ecdysed adults remained high after 2 weeks of starvation. In contrast, feeding was a prerequisite for the decrease of the SCP during prediapause. In postdiapause insects, the SCP increased at high temperatures in spite of the absence of food.

Journal Article↗
PubMed1997

Differential scanning calorimetry studies on an Antarctic nematode (Panagrolaimus davidi) which survives intracellular freezing.

Differential scanning calorimetry was used to characterize thermal events associated with freezing and melting of suspensions and extracts of Panagrolaimus davidi, an Antarctic nematode which can survive intracellular freezing. Nematode suspensions produced a single freezing exotherm with a shoulder on the peak representing the freezing of the nematodes. A shoulder on the peak of melting endotherms indicates the melting of the nematodes and of the water surrounding them. Exotherms were also detected from individual nematodes mounted in liquid paraffin. The freezing of nematodes was very rapid and in marked contrast to that of freezing-tolerant insects and vertebrates, which take hours or days to freeze. Eighty-two percent of the nematodes' body water froze. High levels of survival were obtained in nematodes exposed to temperatures down to -40 degrees C. No additional thermal events were observed after the freezing event and before the melting of samples cooled to -40 degrees C, indicating no changes in the proportion of body water frozen. Ice nucleating activity is present in nematode suspensions but not in supernatants from nematode extracts. No thermal hysteresis activity was detected in nematode extracts.

Animals↗
PubMed1997

Aspects of the Cryobiology of the Intertidal Harpacticoid Copepod Tigriopus brevicornis (O. F. Muller)

Cold-resistance studies of marine invertebrates have concentrated on intertidal sedentary organisms, which are often subjected to subzero air temperatures in winter. Mobile rock pool inhabitants have been rarely studied because such habitats are thought to buffer environmental variation. However, it is not uncommon for small upper-shore rock pools ( approximately 2 by 1 cm) to become completely frozen. Such supralittoral habitats are subject to extreme physicochemical fluctuations especially in salinity (0 to 300 per thousand) and temperature (-1 to +32degreesC) due to evaporation and dilution. The dominant invertebrate in such habitats is the harpacticoid copepod Tigriopus brevicornis. Aspects of the cryobiology of T. brevicornis were investigated using differential scanning calorimetry (DSC). Thermograms obtained from DSC allowed determinations of freeze-onset (supercooling point, SCP), melt-onset, and melt-peak (melting point, MP) temperatures, together with estimation of the proportion of water freezing in the samples. The effects of acclimation salinity, temperature, starvation, and reproductive state on these cryobiological parameters were investigated. Acclimation to increasing salinity depressed the SCP, with the highest salinity (70 per thousand) producing the lowest SCP, melt-onset, and MP temperatures at -27.5, -15.2, and -9.5degreesC respectively. The highest acclimation temperature (20degreesC) produced the lowest SCP (-23.4degreesC). Starvation significantly increased the SCP, melt-onset, and MP temperatures in comparison to fed individuals acclimated to the same salinity. The presence of eggs or ovaries in individual copepods elevated the SCP compared to nongravid females and males. LT50 studies showed that acclimation to high salinity improved the ability of T. brevicornis to survive in frozen seawater. Seventy parts per thousand acclimated individuals had an LT50 of 64.9 h compared with just 1.4 h for 5 per thousand acclimated individuals in frozen seawater at -5degreesC. The study shows that the cold-resistance capabilities of T. brevicornis can be affected by several different factors, and the link between the osmoconforming nature of this species and its cold resistance is discussed. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Responses to desiccation in four Coleopterans from sub-Antarctic South Georgia.

RATES OF WATER LOSS WERE DETERMINED FOR FOUR COLEOPTERA SPECIES: the herbivores Hydromedion sparsutum, Perimylops antarcticus (Family Perimylopidae) and the carnivores Trechisibus antarcticus, Oopterus soledadinus (Family Carabidae) collected during summer from a range of terrestrial habitats at South Georgia. A recording microbalance enabled measurement of individual weight loss with time in <5% r.h. at 10, 20, 30 and 35 degrees C. Adults of T. antarcticus had significantly higher rates of water loss than any other species over all temperatures. Individuals of both herbivores exhibited the slowest water loss rates under the experimental conditions. Within species, rates at 10 or 20 degrees C were slower than at the higher temperatures. Adult P. antarcticus had significantly greater amounts of body water than adult H. sparsutum for each of the four temperatures. Within species and life-stages of both herbivores, body water contents after drying at 10 degrees C were significantly lower than individuals dried at 30-35 degrees C, but no such differences were observed for the carnivores. At each temperature, rates of water loss were negatively correlated with initial live weight in all four species, but this was not the case within species or between adults and larvae. Maximum survival times during desiccation declined as temperature increased, but did not differ between species at 10 degrees C. Over 30-35 degrees C, survival times of both herbivores were significantly longer than either of the carnivores. Smaller insects (e.g. the carabids) had faster rates of water loss than the larger perimylopids under the same environmental conditions. The latter had greater resistance to desiccation than the former. It is suggested that the larger body water content of P. antarcticus enables it to resist desiccation more than the other three species, which correlates with its ecological distribution. Differences in water contents after drying individuals at low and high temperatures may be caused either by the water binding properties of cells and tissues or by reduction in energy stores in order to maintain metabolism at lower environmental temperatures causing a body weight loss. Whilst both herbivores show some physiological adaptations to drying conditions, it is suggested that the two carnivorous beetles may have adapted behaviourally to the South Georgia environment.

Journal Article↗
PubMed1997

[Shortening of the measurement time by 1H-MR turbo spectroscopic imaging of the brain].

PURPOSE: Development of a new technique for reduction of measurement time in 1H-MR spectroscopic imaging of the brain. Optimisation of the sequence parameters in volunteer and in patient examinations and comparison to the results obtained with conventional 2 D-SI. METHODS: Examination of 20 healthy volunteers and 5 patients in a 1.5 T whole-body MR system. In "turbo-spectroscopic imaging" (TSI) sequences, a train of spin-echo signals with different phase encoding is acquired after each 90 degrees excitation. 32 x 32 matrix elements covered a field of view of 20 cm, and additional volume selection was performed by double spin echo excitation. Measurement duration 9 min with acquisition of four phase encoding steps per TR interval, whereas the corresponding 2 D-SI sequence (TR/TE 2000/272 ms) took 30 min. RESULTS: The TSI data sets yielded maps of the regional distribution of metabolite concentrations with a quality comparable to the 2 D-SI results. Signal homogeneity and delineation of brain lesions, however, were superior in conventional spectroscopic imaging. The T2 relaxation of the metabolites required a reduced sampling interval for each phase-encoded echo, and hence the frequency resolution of the corresponding TSI spectra was not always sufficient for separating choline and creatine signals. CONCLUSION: With measurement durations < 10 min the TSI technique allows in clinical studies a combination with single-voxel MRS for accurate quantification and with a diagnostic MRI within a total examination time of less than one hour.

Adult↗
PubMed1997

[MR relaxation time measurements with and without selective fat suppression (SPIR) in endocrine orbitopathy].

PURPOSE: To determine the value and utility of relaxation time measurements with magnetic resonance (MR) imaging in patients with Graves' ophthalmopathy (G.O.). MATERIALS AND METHODS: 20 orbits were studied in control subjects and 58 orbits in patients with G.O. T2 relaxation times of extraocular muscles and retrobulbar fat tissue were calculated. The thickness of the eye muscles was correlated with the calculated T2 times. 18 orbits were measured before and after retro-orbital radiation therapy. RESULTS: Upper limits of determined normal T2 values were 60 ms in extraocular eye muscles and 40 ms in retrobulbar fat tissue. 89% (17/19) of the patients with G.O. had prolonged T2 times in extraocular eye muscles. The retrobulbar fat tissue in 5 of 38 orbits revealed minimal edema with the use of fat saturated sequences. T2 relaxation times decreased significantly (p < 10(-4)) after 10 Gy radiation therapy. No correlation was found between enlargement and T2 relaxation times in extraocular eye muscles (r = 0.44 in patients before radiation therapy). CONCLUSION: In patients with G.O. the determination of the enlargement of extraocular eye muscles in computed tomography is not a sufficient parameter for an antiinflammatory therapy, since CT cannot visualise eye muscle edema. T2 relaxation time measurements with MR imaging allow differentiation between edematous and fibrotic changes. This is the diagnostic method of choice in patients with Graves' ophthalmopathy.

Adipose Tissue↗
PubMed1997

Relationship between cytochrome P-450 induction by rifampicin, hepatic volume and portal blood flow in man.

OBJECTIVE: Induction of hepatic cytochrome P-450-dependent oxidative metabolism is related to an almost identical increase (30%) in both the liver weight and portal blood flow in animals. In humans by contrast, an increased liver blood flow (44%) but no significant increase in liver volume has been reported. DESIGN: Therefore, we studied prospectively the relationship between P-450 induction by rifampicin, hepatic volume and portal blood flow in 10 healthy volunteers. METHODS: After a pre-treatment phase (day 1 to 7) the 10 volunteers received 600 mg/day of rifampicin from day 7 to 12. The urinary 6-beta-hydroxycortisol output as a measure of oxidative metabolism (CYP3A4) and portal blood flow (pulsed Doppler ultrasound) were determined on days 1, 7, 11 and 13. Hepatic magnetic resonance volumetry was performed on days 1 and 13. RESULTS: Urinary 6-beta-hydroxycortisol output increased in all volunteers (P = 0.0051) from a median of 2.15 micrograms/day/kg (1.8-3.3 micrograms/day/kg) on day 1 to 9.9 micrograms/day/kg (5.7-14 micrograms/day/kg) on day 13. In 9 of 10 volunteers induction by rifampicin was related to an increase (P = 0.0218) in liver volume from a median of 1570 cm3 (1390-1830 cm3) to a median of 1690 cm3 (1420-1860 cm3). The portal flow as assessed by colour Doppler ultrasound did not change significantly between day 1 (median 22 cm/s (15-35 cm/s)) and day 13 (median 19 cm/s (16-39 cm/s)). CONCLUSION: A fourfold increase of urinary 6-beta-hydroxycortisol output after induction of cytochrome P-450 by rifampicin is associated with a significant but less than 10% increase in human liver volume. No increase of portal perfusion as assessed by Doppler ultrasound could be detected in this study.

Adult↗
PubMed1996

A gE deleted infectious bovine rhinotracheitis marker vaccine for use in improved bovine herpesvirus 1 control programs.

Based on a glycoprotein E (gE) deleted bovine herpesvirus 1 (BHV1) strain (Kaashoek et al., 1994) a killed virus as well as a modified live virus marker vaccine have been developed that allow differentiation between immunized and BHV1 infected cattle. Safety and efficacy of both vaccines were tested extensively following the current European Union (EU) requirements for the development of bovine vaccines. The minimum vaccine dose, vaccination regimen, route of administration and duration of immunity were evaluated for both vaccines in comprehensive vaccination/challenge trials in cattle. The most potent adjuvant formulation for the killed virus vaccine was also selected by experimental challenge infections. For the modified live virus marker vaccine it could be demonstrated that maternally derived BHV1 specific antibodies did not interfere with vaccination. Safety could be demonstrated for both the killed virus and the modified live virus vaccine in all target animal categories including veal calves, beef cattle, bulls, heifers and dairy cattle, including pregnant animals.

Animals↗
PubMed1995

[1H-MR spectroscopic imaging in patients with clinically diagnosed Alzheimer's disease].

PURPOSE: To detect regional differences in accompanying metabolic changes, 1H-Magnetic Resonance Spectroscopic Imaging (MRSI) was performed in 16 patients with Alzheimer's disease (AD); the clinical diagnosis was based upon DSM-III-R and NINCDS-ADRDA guidelines. METHODS: In the hippocampal region metabolic maps of the local distribution of N-acetylaspartate (NAA), choline (Cho), creatine compounds (P(Cr)) and lactate were determined. Ratios of Cho/NAA, (P)Cr/NAA and Cho/(P)Cr calculated from selected hippocampal spectra were compared to those from healthy volunteers (n = 17). RESULTS: AD patients demonstrated an increase of Cho/NAA and (P)Cr/NAA ratios caused by increased choline compounds and decreased NAA. These alterations were observed in 11/12 cases in the hippocampal and in 7/12 in the temporo-occipital region. Hippocampal Cho/NAA ratios (0.56 +/- 0.19) were significantly elevated compared with controls (0.33 +/- 0.04; p < 0.0001). CONCLUSION: The observed elevation of choline compounds in the hippocampus supports the hypothesis that alterations in the cholinergic system play an important role in Alzheimer's disease. The observed reduction of NAA is due to neuronal degeneration.

Aged↗
PubMed1995

Safety aspects in the development of an infectious bovine rhinotracheitis marker vaccine.

Clinical trials in cattle demonstrated that the IBR marker modified live vaccine based on the gE-deleted IBR strain Difivac is immunogenic and safe for bovines of all ages. Potential effects of the vaccine virus have also been tested in swine and sheep and proved safe for these species as well. For evaluation of other environmental aspects, the spread of the vaccine virus after immunisation was investigated. The data indicated that the vaccine virus may be shed by immunised animals but that it has a limited ability to pass from animal to animal. It was also demonstrated that the attenuated Difivac strain does not revert to virulence during calf passage. Preliminary results indicated that the gE-deleted vaccine virus of the IBR marker vaccine cannot be reactivated after dexamethasone treatment, an important advantage for a vaccine strain. Furthermore, immunisation with the Difivac strain reduced the ability of a superinfecting challenge virus to become latent or to be reactivated.

Animals↗
PubMed1994

Mitochondrial encephalomyopathy: correlation of P-31 exercise MR spectroscopy with clinical findings.

PURPOSE: To evaluate the sensitivity of standardized exercise phosphorus-31 magnetic resonance (MR) spectroscopy in screening for subclinical muscle involvement in mitochondrial encephalomyopathy and to estimate if changes seen at biopsy have functional consequences. MATERIALS AND METHODS: Exercise MR spectroscopy was performed in 52 examinations of 18 healthy volunteers and 14 patients with defects of mitochondrial respiratory chain enzymes. Calculation and kinetic analysis of the phosphocreatine (PCr) index and pH time courses were standardized with a microcomputer program. RESULTS: PCr index scores and conventional test scores matched in 10 of 14 cases. No obvious correlation existed between pH parameters and clinical score. Muscle affection, according to pH parameter score, was rated moderate (n = 3), severe (n = 1), or maximum (n = 2) in six of 14 cases in which clinical test scores showed only mild affection. CONCLUSION: Exercise MR spectroscopic PCr index parameters provide diagnostic information on skeletal muscle involvement in patients with mitochondrial encephalopathy. The sensitivity of the PCr index parameter seems equal or superior to that of conventional diagnostic tests. The role of pH parameters, however, has yet to be defined.

Adult↗
PubMed1992

Cerebrospinal fluid protein variations in common to Alzheimer's disease and schizophrenia.

Analysis of silver stained two-dimensional (2D) gels of cerebrospinal fluid (CSF) from 27 patients with schizophrenia (SCZ) and 10 patients with Alzheimer's disease (AD) revealed an increase in the relative amount of a polypeptide of 18,000M(r) and isoelectric point of 6.5 when compared to the appropriate controls. This protein was identified by its electrophoretic characteristics and by immune analysis of Western blots as an isoform of alpha-2 haptoglobin, provisionally identified as alpha-2FS haptoglobin. Alzheimer's disease versus control CSF samples showed a 6.8-fold increase in the percent mean density value of this haptoglobin isoform (n = 10 AD vs 11 control; P > 0.025) while a 4.4-fold increase was observed in the schizophrenic patients (n = 17 SCZ vs 10 control; P > 0.001). Two additional polypeptides (proteins '127' and '128') of 40,000 M(r) and isoelectric points 5.7 and 5.9, respectively, described previously by this laboratory, were found in the CSF of 27% of schizophrenics, 23% of the Alzheimer's disease patients, and 4% of the controls in the current study. The presence of proteins 127 and 128, as well as the increased concentrations of alpha-2 haptoglobin in the CSF of Alzheimer's disease and schizophrenic patients, may be useful as diagnostic biological markers. They may also indicate a common pathophysiology between these diseases.

Acute-Phase Proteins↗
PubMed1990

Cold resistance in all life stages of two blowfly species (Diptera, Calliphoridae).

1. Freezing was lethal in the eggs, larvae, pupae and adults of the blowflies Calliphora vicina R-D. and Calliphora vomitoria (L.), but varying degrees of supercooling were found. 2. Cold resistance (as determined by their supercooling capacity) was greatest in eggs (to c. -25 degrees C), and moderate in other life stages (range -7 to -13 degrees C), which was evident from the distributions of their supercooling points. 3. Water contents of all life stages varied from 63% to 77% of fresh weight; pupae of C. vomitoria contain the smallest proportion of water. No relationship between the amount of body water and supercooling ability was detected. 4. Glucose was the major compound in all life stages of C. vicina, with a maximum concentration of 8.22 micrograms mg-1 fresh weight in the adults. In addition, five other potential cryoprotectants occurred in concentrations greater than 0.1% of fresh weight. No correlation between solute concentration and supercooling was observed. 5. Both C. vicina and C. vomitoria have sufficient cold hardiness to avoid lethal freezing in sheltered habitats in southern Britain, which may render diapause unnecessary in both species.

Animals↗