Role of ultrasound in detection of lymph nodes metastasis in gynecological cancers: systematic review and meta-analysis

OBJECTIVE

To assess the diagnostic performance of transvaginal ultrasound (TVUS) for preoperative evaluation of lymph node metastasis in gynecological cancers.

METHODS

A systematic review and meta-analysis was performed. All studies published between January 1990 to May 2023 evaluating the role of ultrasound for detecting lymph node metastasis (index test) in gynecological cancers, using histopathological analysis, as reference standard were included. Quality was assessed using QUADAS-2. Pooled sensitivity, specificity and diagnostic odds ratio of TVUS were estimated.

RESULTS

The search identified 2638 citations. Eight studies comprising 967 women were included. The mean prevalence of pelvic lymph nodes metastasis was 24.2%, [14%-65.6%]. The risk of bias was low for most domains assessed. Overall pooled sensitivity, specificity and diagnostic odds ratio of TVUS were 41% (95% confidence interval [CI] =26%-58%), 98% (95%CI=93%-99%) and 32 (95%CI=14-72), respectively. Heterogeneity in TVUS evaluation was high between studies, both for sensitivity and specificity. No publication bias was found (p=0.46).

CONCLUSION

TVUS showed a high-pooled specificity for the detection of pelvic lymph node metastasis in gynecological cancers. However, pooled sensitivity was low. This article is protected by copyright. All rights reserved.

Response to OKN-007 and NAC in a Patient with Unilateral Hearing Loss and Chronic Tinnitus from Vestibular Schwannoma

BACKGROUND

Tinnitus is the perception of sound in the absence of external acoustic stimulation. Being one of the most common diseases of the ear, it has a global prevalence ranging from 4.1 to 37.2%. To date, it has been difficult to treat tinnitus as its pathophysiology is poorly understood and there are limited treatment options.

OBJECTIVE

To investigate the effect of OKN-007 (also known as HPN-07), a nitrone-based investigational drug, in combination with oral N-acetylcycsteine (NAC), for the treatment of hearing loss and chronic tinnitus under an individual expanded access protocol.

PATIENT CASE

We report the case of a patient who presented with left-sided ear fullness, mild tinnitus, and mild high frequency sensorineural hearing loss with 100% word recognition. A large enhancing mass seen on MRI revealed a vestibular schwannoma. He underwent subtotal resection of the tumor resulting in a moderate-to-profound sensorineural hearing loss and catastrophic tinnitus. The patient was treated with intravenous OKN-007 at 60 mg/kg dosed three times per week and oral NAC 2500 mg twice daily.

RESULTS

Post-treatment audiometric testing revealed an average of 16.66 dB in hearing threshold improvement in three frequencies (125, 250 and 500 Hz) with residual hearing in the affected left ear. His tinnitus loudness matching improved from 90 dB to 19 dB post-treatment. His Tinnitus Handicap Inventory improved from 86/100 (Catastrophic) to 40/100 (Moderate). He also experienced improvements in sleep, concentration, hearing, and emotional well-being, and reported significantly decreased levels of tinnitusrelated distress.

CONCLUSIONS

This case report highlights the feasibility and therapeutic potential of the combination of OKN-007 and NAC in treating hearing loss and tinnitus that warrants further investigation.

CTNI-51. FEASIBILITY AND SAFETY OF NEUROSURGICAL RESECTION AND INTRA-OPERATIVE RADIATION THERAPY USING THE XOFT AXXENT ELECTRONIC BRACHYTHERAPY SYSTEM AND BEVACIZUMAB IN RECURRENT GLIOBLASTOMA

Glioblastoma (GBM) is the most common and aggressive primary brain tumor. External beam radiation therapy (EBRT) is widely recognized as an effective treatment for primary GBM. EBRT applied after GBM resection is associated with an increase in overall survival. Beyond upfront therapy with radiation and temozolomide chemotherapy, there is no standard therapy that has been proven effective. Re-irradiation with ERBT is minimally effective and with significant comorbidities. Our study uses IORT at the time of re-resection in patients who have recurrent, operable GBM after failure of who received primary EBRT and temozolamide in their first course of treatment. IORT allows the delivery of a large effective radiation dose applied directly to the tumor bed at the time of resection. This affords direct radiation to be delivered to the micro- and macroscopic tumor remnants in the vicinity of the resection cavity immediately following gross resection. In contrast, the more distant, surrounding brain tissue does not receive high radiation exposure. This Phase II study continues to accrue subjects with the primary endpoint of overall survival and several secondary endpoints that includes progression free survival, quality of life, and adverse events/safety. To date, five patients have been treated on this protocol. The technical feasibility and safety of administering intraoperative radiation with the Xoft System has been established in this cohort. Preliminary GLIOX Trial findings demonstrate the safety and feasibility of using the Xoft Axxent® Electronic Brachytherapy System to administer intracranial radiation during resection of recurrent glioblastomas. We will report new and expansive study results to include these early findings.

BETA PRIME: Phase I study of AdAPT-001 as monotherapy and combined with a checkpoint inhibitor in superficially accessible, treatment-refractory solid tumors

AdAPT-001 is an investigational therapy consisting of a replicative type 5 adenovirus armed with a TGF-β receptor-immunoglobulin Fc fusion trap, designed to neutralize isoforms 1 and 3 of the profibrotic and immunosuppressive cytokine, TGF-β. In preclinical studies with an immunocompetent mouse model, AdAPT-001 eradicated directly treated 'cold' tumors as well as distant untreated tumors, and, from its induction of systemic CD8+ T cell-mediated antitumor immunity, protected the mice from rechallenge with tumor cells. AdAPT-001 also sensitized resistant tumors to checkpoint blockade. This manuscript describes the rationale and design of the first-in-human phase I, dose-escalation and dose-expansion study of AdAPT-001 alone and in combination with a checkpoint inhibitor in adults with treatment-refractory superficially accessible solid tumors.

[Interpretation of ventilator curves in patients with acute respiratory failure]

Mechanical ventilation is a therapeutic intervention involving the temporary replacement of ventilatory function with the purpose of improving symptoms in patients with acute respiratory failure. Technological advances have facilitated the development of sophisticated ventilators for viewing and recording the respiratory waveforms, which are a valuable source of information for the clinician. The correct interpretation of these curves is crucial for the correct diagnosis and early detection of anomalies, and for understanding physiological aspects related to mechanical ventilation and patient-ventilator interaction. The present study offers a guide for the interpretation of the airway pressure and flow and volume curves of the ventilator, through the analysis of different clinical scenarios.

Hydrodynamics of nanoscopic capillary waves

The dynamics of nanoscopic capillary waves on simple liquid surfaces is analyzed using molecular dynamics simulations. Each Fourier mode of the surface is obtained from the molecular positions, and its time behavior compared with the hydrodynamic prediction. We trace the transition from propagating to overdamped modes, at short wavelengths. The damping rate is in very good agreement with the hydrodynamic theory up to surprisingly small wavelengths, of about four molecular diameters, but only if the wave number dependent surface tension is considered. At shorter scales, surface tension hydrodynamics break down and we find a transition to a molecular diffusion regime.

Success rate and patient satisfaction with the Essure™ sterilisation in an outpatient setting: a prospective study of 857 women

After 857 women with Essure system inserted for tubal obstruction as a method of sterilization in an outpatient setting, insertion is achieved in close to 99% of the women. Physician described the procedure as very difficult in 15% of the cases, mainly due to anatomical tubal anomalis or tubal spasm, and women felt highly satisfied in all cases.

Bovine trypanosomosis in the Bolivian Pantanal

Trypanosomosis caused by Trypanosoma vivax has been a constraint for cattle production in the Bolivian lowlands, since it was introduced in 1996. Flooded areas like the Bolivian Pantanal have a suitable environment for the presence and transmission of Salivarian trypanosomes and farmers from that region often report trypanosomosis-like problems on their farms. The objective of the present study, therefore, was to characterize the epidemiology of bovine trypanosomosis in the Bolivian Pantanal. In order to achieve this objective, 202 cattle from the province of Angel Sandoval and 209 cattle from the province of German Busch were randomly sampled (the Pantanal is located in both provinces). Twenty-nine farms in both provinces were visited, the farmers interviewed, and biologic samples collected from their cattle. Samples were submitted for parasitological and PCR evaluation and the prevalence of bovine trypanosomosis was estimated for each province. Laboratory results were correlated with the sampled animals packed cell volume (PCV) and body condition (BC) scores and the observed T. vivax parasites measured for morphometry analysis. Results from this study show differences in morphometric measures between T. vivax parasites from each province. Differences between provinces were also observed in the T. vivax-related disease situation. While in Angel Sandoval the PCV and BC of T. vivax-affected animals were significantly lower than those of the T. vivax-negative animals, in German Busch no differences were observed in the PCV and BC of T. vivax-positive or negative animals. Animal prevalence of T. vivax in Angel Sandoval was 27.79% (95% CI: 14.52-44.28) and in German Busch was 19.03% (95% CI: 9.19-30.75). The T. evansi animal prevalence in each province was 0.99% (95% CI: 0.27-2.99) and 5.71% (95% CI: 2.43-12.19), respectively. Based on questionnaire and laboratory results, it was concluded that trypanosomosis is a primary constraint for cattle production in the Bolivian Pantanal.

Sensitivity of different Trypanosoma vivax specific primers for the diagnosis of livestock trypanosomosis using different DNA extraction methods

There are several T. vivax specific primers developed for PCR diagnosis. Most of these primers were validated under different DNA extraction methods and study designs leading to heterogeneity of results. The objective of the present study was to validate PCR as a diagnostic test for T. vivax trypanosomosis by means of determining the test sensitivity of different published specific primers with different sample preparations. Four different DNA extraction methods were used to test the sensitivity of PCR with four different primer sets. DNA was extracted directly from whole blood samples, blood dried on filter papers or blood dried on FTA cards. The results showed that the sensitivity of PCR with each primer set was highly dependant of the sample preparation and DNA extraction method. The highest sensitivities for all the primers tested were determined using DNA extracted from whole blood samples, while the lowest sensitivities were obtained when DNA was extracted from filter paper preparations. To conclude, the obtained results are discussed and a protocol for diagnosis and surveillance for T. vivax trypanosomosis is recommended.

Aggregation models at high packing fraction

Dense phases of micellar aggregates have strong molecular correlation at two different levels: that of the molecules forming a micelle and that between micelles, leading to a possible phase transition from a micellar fluid to a micellar crystal. The global phase diagram may also include lamellar and other dense phases, which do not have a micellar structure. We present here a generic approach to deal with these systems through a two-level density-functional description, to first describe an isolated micellar aggregate and then the dense micellar system, obtaining the free energy in a self-consistent way from the molecular interactions. Nonmicellar dense phases are included with the same density-functional approach applied at the first level. The results are shown to be very accurate for a one-dimensional model with exact solution, and the method is then applied to a three-dimensional amphiphile model that had been successfully used to describe the properties of diluted amphiphile solutions.

High throughput liquid chromatography-mass spectrometry assessment of the metabolic activity of commercially available hepatocytes from 96-well plates

We have assessed the metabolic activity of freshly isolated and commercially preserved rat, monkey, and human primary hepatocytes in a 96 well plate format utilizing eight beta-adrenolytic drugs as model compounds. Sample introduction from 96 well plates, HPLC solvent delivery, mass spectrometric (MS) detection, and/or UV detection were fully integrated and operated unattended. After drugs were incubated with hepatocytes for three or six hr, LC-MS analyses were carried out to determine the amount of drug which was not metabolized. Two LC-MS methods were used which had a sample throughput of 4 samples/hr and 12 samples/hr. Under optimal conditions, this hepatic assay could screen 300 samples/week or 1200 samples/month. Although freshly isolated hepatocytes were more active, commercially available rat, monkey, and human primary isolated hepatocytes metabolized drug substrates in similar relative rank orders. This drug-hepatocyte assay provides useful information for prioritizing pharmaceutical leads in relative rank orders or in a high/low manner according to their resistance toward liver metabolism.

Mitochondrial Ca2+ transients in cardiac myocytes during the excitation-contraction cycle: effects of pacing and hormonal stimulation

Using laser scanning confocal microscopy, our objective was to measure mitochondrial, nuclear, and cytosolic free ionized Ca2+ in adult rabbit cardiac myocytes loaded with Ca2+-indicating fluorophores. When myocytes were loaded with Fluo 3 at 37 degrees C, the fluorophore was loaded extensively into the cytosol and nucleus, but poorly into mitochondria, and Fluo 3 fluorescence transients after field stimulation were confined to the cytosol and nucleus. In contrast, after loading at 4 degrees C, Fluo 3 also entered mitochondria, and large transients of mitochondrial Fluo 3 fluorescence then occurred after stimulation. Isoproterenol (1 microM) increased the magnitude of Ca2+ transients and their subsequent rate of decay, an effect more marked in the cytosol and nucleus than in mitochondria. As pacing frequency was increased from 0.5 to 2 Hz, diastolic mitochondrial Ca2+ rose markedly in the absence but not in the presence of isoproterenol. Resting Ca2+ estimated by Indo 1 ratio imaging using UV/visible laser scanning confocal microscopy was about 200 nM in all compartments. During field stimulation, Ca2+ transiently increased to 671, 522, and 487 nM in cytosol, interfibrillar mitochondria, and perinuclear mitochondria, respectively. Isoproterenol increased these respective peak values to 1280, 750, and 573 nM. These results were consistent with those obtained in Fluo 3 experiments. We conclude that rapid mitochondrial Ca2+ transients occur during excitation-contraction coupling in adult rabbit cardiac myocytes, which may be important in matching mitochondrial metabolism to myocardial ATP demand during changes in cardiac output.

Mitochondrial free calcium transients during excitation-contraction coupling in rabbit cardiac myocytes

Mitochondrial free Ca2+ may regulate mitochondrial ATP production during cardiac exercise. Here, using laser scanning confocal microscopy of adult rabbit cardiac myocytes co-loaded with Fluo-3 to measure free Ca2+ and tetramethylrhodamine methylester to identify mitochondria, we measured cytosolic and mitochondrial Ca2+ transients during the contractile cycle. In resting cells, cytosolic and mitochondrial Fluo-3 signals were similar. During electrical pacing, transients of Fluo-3 fluorescence occurred in both the cytosolic and mitochondrial compartments. Both the mitochondrial and the cytosolic transients were potentiated by isoproterenol. These experiments show directly that mitochondrial free Ca2+ rises and falls during excitation-contraction coupling in cardiac myocytes and that changes of mitochondrial Ca2+ are kinetically competent to regulate mitochondrial metabolism on a beat-to-beat basis.

The pH paradox in ischemia-reperfusion injury to cardiac myocytes

During myocardial ischemia, a large reduction of tissue pH develops, and tissue pH returns to normal after reperfusion. In recent studies, we evaluated the role of pH in ischemia/reperfusion injury to cultured cardiac myocytes and perfused papillary muscles. Acidosis (pH < or = 7.0) protected profoundly against cell death during ischemia. However, the return from acidotic to normal pH after reperfusion caused myocytes to lose viability. This worsening of injury is a 'pH paradox' and was mediated by changes of intracellular pH (pH(i)), since manipulations that caused pH(i), to increase more rapidly after reperfusion accelerated cell killing, whereas manipulations that delayed the increase of pH(i) prevented loss of myocyte viability. Specifically, inhibition of the Na+/H+ exchanger with dimethylamiloride or HOE694 delayed the return of physiologic pH(i) after reperfusion and prevented reperfusion-induced cell killing to both cultured myocytes and perfused papillary muscle. Dimethylamiloride and HOE694 did not reduce intracellular free Ca2+ during reperfusion. By contrast, reperfusion with dichlorobenzamil, an inhibitor of Na+/Ca2+ exchange, decreased free Ca2+ but did not reduce cell killing. Thus, the pH paradox is not Ca(2+)-dependent. Our working hypothesis is that ischemia activates hydrolytic enzymes, such as phospholipases and proteases, whose activity is inhibited at acidotic pH. Upon reperfusion, the return to normal pH releases this inhibition and hydrolytic injury ensues. Increasing pH(i) may also induce a pH-dependent mitochondrial permeability transition and activate the myofibrillar ATPase, effects that increase ATP demand and compromise ATP supply. In conclusion, acidotic pH is generally protective in ischemia, whereas a return to physiologic pH precipitates lethal reperfusion injury to myocytes.

Distribution of electrical potential, pH, free Ca2+, and volume inside cultured adult rabbit cardiac myocytes during chemical hypoxia: a multiparameter digitized confocal microscopic study

Exploiting the optical sectioning capabilities of laser scanning confocal microscopy and using parameter-specific fluorescent probes, we determined the distribution of pH, free Ca2+, electrical potential, and volume inside cultured adult rabbit cardiac myocytes during ATP depletion and reductive stress with cyanide and 2-deoxyglucose ("chemical hypoxia"). During normoxic incubations, myocytes exhibited a cytosolic pH of 7.1 and a mitochondrial pH of 8.0 (delta pH = 0.9 units). Sarcolemmal membrane potential (delta psi) was -80 mV, and mitochondrial delta psi was as high as -100 mV, yielding a mitochondrial protonmotive force (delta p) of -155 mV (delta P = delta psi - 60 delta pH). After 30 min of chemical hypoxia, mitochondrial delta pH decreased to 0.5 pH units, but mitochondrial delta psi remained essentially unchanged. By 40 min, delta pH was collapsed, and mitochondrial and cytosolic free Ca2+ began to increase. Mitochondrial and sarcolemmal delta psi remained high. as Ca2+ rose, myocytes shortened, hypercontracted, and blebbed with a 30% decrease of cell volume. After hypercontraction, extensive mitochondrial Ca2+ loading occurred. After another few minutes, mitochondrial depolarized completely and released their load of Ca2+. After many more minutes, the sarcolemmal permeability barrier broke down, and viability was lost. These studies demonstrate a sequence of subcellular ionic and electrical changes that may underlie the progression to irreversible hypoxic injury.

Inhibition of Na+/H+ exchange preserves viability, restores mechanical function, and prevents the pH paradox in reperfusion injury to rat neonatal myocytes

Rat neonatal myocytes exposed to 2.5 mM CaCN and 20 mM 2-deoxyglucose at pH 6.2 (chemical hypoxia) quickly lose viability when pH is increased to 7.4, with or without washout of inhibitors--a 'pH paradox'. In this study, we evaluated the effect of two Na+/H+ exchange inhibitors (dimethylamiloride and HOE694) and a Na+/Ca2+ exchange inhibitor (dichlorobenzamil) on pH-dependent reperfusion injury. Intracellular free Ca2+ and electrical potential were monitored by laser scanning confocal microscopy of rat neonatal cardiac myocytes grown on coverslips and co-loaded with Fluo-3 and tetramethylrhodamine methylester. After 30-60 min of chemical hypoxia at pH 6.2, mitochondria depolarized and Ca2+ began to increase uniformly throughout the cell. Free Ca2+ reached levels estimated to exceed 2 microM by 4 h. Washout of inhibitors at pH 7.4 (reperfusion), with or without dichlorobenzamil, killed most cells within 60 min, despite a marked reduction of Ca2+ in dichlorobenzamil-treated cells. Reperfusion at pH 7.4 in the presence of 75 microM dimethylamiloride or 20 microM HOE694, or at pH 6.2, prevented cell death. HOE694-treated cells placed into culture medium recovered mitochondrial membrane potential. In most cells, this occurred before normal Ca2+ was restored. Contracted myocytes re-extended over a 24-h-period. By 48 hours, most cells contracted spontaneously and showed normal Ca2+ transients. Our results indicate that Na+/H+ exchange inhibition protects against pH-dependent reperfusion injury and facilitates full recovery of cell function.

Intracellular pH and Ca2+ homeostasis in the pH paradox of reperfusion injury to neonatal rat cardiac myocytes

Ischemia is characterized by anoxia and a large decrease of tissue pH. After a critical period of ischemia, reperfusion precipitates irreversible injury. Previous work showed that reperfusion injury to cultured neonatal myocytes was precipitated by a rapid return to physiological pH, a "pH paradox" (Bond, J., B. Herman, and J. Lemasters. Biochem. Biophys. Res. Commun. 179: 798-803, 1991). The aim of this study was to measure intracellular pH (pHi) and cytosolic free Ca2+ during the pH paradox of reperfusion injury to cultured neonatal rat cardiac myocytes. pHi and free Ca2+ were measured by ratio imaging of 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein and fura 2 fluorescence. To simulate ATP depletion and acidosis of ischemia, myocytes were incubated with 20 mM 2-deoxyglucose plus 2.5 mM NaCN at pH 6.2. During simulated ischemia, pHi dropped to < 6.5 and subsequently remained constant. During this time, some blebbing but little hypercontraction occurred. After 3 or 4 h of simulated ischemia, inhibitors were removed and cells were incubated at pH 7.4 to simulate reperfusion. pHi began to increase, blebbing accelerated, and myocytes hypercontracted. As pHi increased, viability was lost. The same occurred if pH was increased but metabolic inhibitors were not removed. Monensin, a Na(+)-H+ ionophore, accelerated the increase of pH after reperfusion and hastened cell killing. Hypercontraction, blebbing, and loss of viability did not occur when inhibitors were removed at pH 6.2 or in the presence of dimethylamiloride, an inhibitor of Na(+)-H+ exchange. Protection was associated with maintenance of an acidotic pHi. Free Ca2+ progressively increased during simulated ischemia. After simulated reperfusion, free Ca2+ increased further.(ABSTRACT TRUNCATED AT 250 WORDS)

A digitized-fluorescence-imaging study of mitochondrial Ca2+ increase by doxorubicin in cardiac myocytes

The objective of the present study was to investigate the role of mitochondrial Ca2+ in doxorubicin-induced cell injury. The effect of doxorubicin on cultured cells was investigated by digitized fluorescence imaging. The Ca2+ sensitive fluorescent dye fura-2 was used to estimate cytosolic, mitochondrial and total cellular Ca2+. Rhodamine 123 was used to estimate the mitochondrial membrane potential, and cellular ATP was determined by h.p.l.c. The data showed that doxorubicin induced greater-than-2-fold increases in mitochondrial Ca2+ before changes in cytosolic Ca2+ could be detected. An increase in mitochondrial Ca2+ paralleled the observed dissipation in mitochondrial membrane potential. Cellular ATP levels appeared to decrease as a result of mitochondrial dysfunction, which in turn produced greater-than-2-fold increases in cytosolic Ca2+. The data suggest that doxorubicin-induced alterations in mitochondrial Ca2+ homoeostasis are associated with a dissipation in energy conservation, which may result in cell injury.

Radiation-induced syntheses in cometary simulated models

The behavior of an aqueous-dominant multicomponent cometary model is examined at high doses of ionizing radiation. The system is composed of a water mixture of HCN (0.2 mol dm-3), CH3CN (0.04 mol dm-3), C2H5CN (0.02 mol dm-3), CH3OH (0.12 mol dm-3) and HCO2H (0.01 mol dm-3. It was exposed to gamma rays at doses up to 18.5 MGy. The chemical kinetic database used in the computer treatment of experimental data consists of 79 reactions. A complex mixture of products has been synthesized: gases, amino acids, carboxylic acids and polymeric material. The results suggest that the pristine material in cometary nuclei may have been chemically altered by the action of cosmic rays and embedded radionuclides.

Mitochondrial regulation of superoxide by Ca2+: an alternate mechanism for the cardiotoxicity of doxorubicin

Mitochondrial Ca2+ accumulation and the formation of reactive oxygen species are processes dependent on the electron transport system. The production of superoxide by respiring rat heart mitochondria was decreased by either chelating extramitochondrial Ca2+ with EGTA or by blocking mitochondrial Ca2+ uptake with ruthenium red. Mitochondrial experiments with doxorubicin showed an enhanced stimulation of reactive oxygen species, which was also inhibited by EGTA or ruthenium red. Myocardial cell cultures treated with doxorubicin showed an enhanced formation of intracellular reactive oxygen species, which preceded cell damage. Ruthenium red not only attenuated the enhanced formation of intracellular reactive oxygen species, but also increased cell viability. The relationship between mitochondrial Ca2+ transport and the formation of superoxide suggests that a disruption in mitochondrial Ca2+ homeostasis by doxorubicin may be involved in the release of reactive oxygen species and its cardiotoxicity.

Influence of progressive defoliation of a grass sward on the eating behaviour of cattle

Changes in sward structure, diet selection and eating behaviour of cattle (grazing time, biting, bite size and estimated intake) were studied as contrasting swards of Setaria anceps cv. Kazungula were progressively defoliated. In one experiment three replicates in time of 9-week autumn regrowths were grazed down over 14-day periods, and a further two time replicates of 5-week regrowths were grazed down over 10-day periods in spring. A second experiment investigated the causes of changes in grazing behaviour. In the early stages of defoliation cows selected mainly leaf (> 80%) from the uppermost layers of the sward. As the quantity of leaf on offer became less, the animals took smaller bites, increased the time spent grazing (up to a mean of 646 min in autumn and 593 min in spring), and increased the rate of biting (up to 62.4 and 59.4 eating bites min-1 in autumn and spring respectively) and the total number of eating bites (up to 39,500 and 34,000 day-1 in autumn and spring). At this stage bulk in the rumen appeared to limit intake of herbage. Peak grazing time and highest number of bites occurred when leaf yields averaged 1000 kg dry matter ha-1, although total yield and dry green yield varied between swards. In the later stages of defoliation, grazing time and eating bites declined and, together with a reduced bite size (as low as 66 and 79 mg organic matter per bite eaten in experiments 1 and 2 respectively), resulted in a low intake of herbage. Stem and senescent material in the diet increased up to 77%, but bulk was not the major cause of reduced intake. Nitrogen and mineral levels appeared sufficient for maximum intake. Low leaf density prevented animals harvesting large quantities of herbage from the swards. It was concluded that leaf is the most important component of the sward and that leaf yield, percentage leaf and bulk density of green material (leaf and stem) are the major sward factors influencing intake by grazing animals.