ABSTRACT
BACKGROUND: Since the development of minimally invasive surgery (MIS), laparoscopic and robotic approaches have been widely adopted. However, little has been published detailing the learning curve of MIS, especially in infants. OBJECTIVE: To quantify the learning curve of laparoscopic (LP) and robot-assisted laparoscopic pyeloplasty (RAL-P) for treatment of uretero-pelvic junction obstruction (UPJO) in infants evidenced by number of cases, operative time, success and complications. PATIENTS AND METHODS: Between 2009 and 2017, we retrospectively reviewed pyeloplasty cases for treatment of UPJO in infants at three academic institutions. The primary outcome was success. Secondary outcomes were UPJO recurrence, complications, and operative time as a surrogate of skill acquisition. Continuous variables were analyzed by t test, Welch-test, and one-way ANOVA. Non-continuous variables were analyzed by Chi-squared test or Fisher's exact test. Learning curves (LC) were studied by r-to-z transformation and CUSUM. RESULTS: Thirty-nine OP, 26 LP, and 39 RAL-P had mean operative times (OT) of 106, 121, and 151 min, respectively. LCs showed plateau in OT after 18 and 13 cases for LP and RAL-P, respectively. RAL-P showed a second phase of further improvements after 37 cases. At 16 months follow-up, there were similar rates of success and complications between the three groups. CONCLUSIONS: Despite different duration of learning phases, proficiency was achieved in both LP and RAL-P as evidenced by stabilization of operative time and similar success rates and complications to OP. Before and after achievement of proficiency, LP and RAL-P can be safely learned and implemented for treatment of UPJO in infants.
Subject(s)
Laparoscopy , Robotic Surgical Procedures , Robotics , Ureteral Obstruction , Humans , Infant , Kidney Pelvis/surgery , Learning Curve , Retrospective Studies , Treatment Outcome , Ureteral Obstruction/surgery , Urologic Surgical ProceduresABSTRACT
In pursuit of perfect infrared (IR) radiation absorbers, we examined quasi-crystal structures made of graphite wires. Simulations on an array of subwavelength graphitic cages and cage-within-cage frameworks indicate a flat absorption coefficient between 10-30 µm. The concept could be scaled up through the 50-120 µm [far-IR, terahertz (THz)] region by a proper structural design. For cage-within-cage, the IR radiation energy is funneled toward the inner cage, resulting in a rather hot structure. At longer wavelengths (microwave region), the electrical conductivity dominates the negative dielectric effect, and experiments with copper cages indicate scattering resonances. Graphitic structures allude to some absorption even at microwave frequencies. Applications are envisioned as anti-fogging surfaces, adaptable electromagnetic shields, energy harvesting, and efficient absorbers in the far-IR (THz frequencies).
ABSTRACT
Successive locations of individual large earthquakes (Mw > 5.5) over years to centuries can be difficult to explain with simple Coulomb stress transfer (CST) because it is common for seismicity to circumvent nearest-neighbour along-strike faults where coseismic CST is greatest. We demonstrate that Coulomb pre-stress (the cumulative CST from multiple earthquakes and interseismic loading on non-planar faults) may explain this, evidenced by study of a 667-year historical record of earthquakes in central Italy. Heterogeneity in Coulomb pre-stresses across the fault system is >±50 bars, whereas coseismic CST is <±2 bars, so the latter will rarely overwhelm the former, explaining why historical earthquakes rarely rupture nearest neighbor faults. However, earthquakes do tend to occur where the cumulative coseismic and interseismic CST is positive, although there are notable examples where earthquake propagate across negatively stressed portions of faults. Hence Coulomb pre-stress calculated for non-planar faults is an ignored yet vital factor for earthquake triggering.
ABSTRACT
The 28th December 1908 Messina earthquake (Mw 7.1), Italy, caused >80,000 deaths and transformed earthquake science by triggering the study of earthquake environmental effects worldwide, yet its source is still a matter of debate. To constrain the geometry and kinematics of the earthquake we use elastic half-space modelling on non-planar faults, constrained by the geology and geomorphology of the Messina Strait, to replicate levelling data from 1907-1909. The novelty of our approach is that we (a) recognise the similarity between the pattern of vertical motions and that of other normal faulting earthquakes, and (b) for the first time model the levelling data using the location and geometry of a well-known offshore capable fault. Our results indicate slip on the capable fault with a dip to the east of 70° and 5 m dip-slip at depth, with slip propagating to the surface on the sea bed. Our work emphasises that geological and geomorphological observations supporting maps of capable non-planar faults should not be ignored when attempting to identify the sources of major earthquakes.
ABSTRACT
The Soil Moisture Active and Passive (SMAP) mission, launched by the National Aeronautics and Space Administration (NASA) on 31st January 2015, was designed to provide global soil moisture every 2 to 3 days at 9 km resolution by downscaling SMAP passive microwave observations obtained at 36 km resolution using active microwave observations at 3 km resolution, and then retrieving soil moisture from the resulting 9 km brightness temperature product. This study evaluated the SMAP Active/Passive (AP) downscaling algorithm together with other resolution enhancement techniques. Airborne passive microwave observations acquired at 1 km resolution over the Murrumbidgee River catchment in south-eastern Australia during the fourth and fifth Soil Moisture Active Passive Experiments (SMAPEx-4/5) were used as reference data. The SMAPEx-4/5 data were collected in May and September 2015, respectively, and aggregated to 9 km for direct comparison with a number of available resolution-enhanced brightness temperature estimates. The results show that the SMAP AP downscaled brightness temperature had a correlation coefficient (R) of 0.84 and Root-Mean-Squared Error (RMSE) of ~10 K, while SMAP Enhanced, Nearest Neighbour, Weighted Average, and the Smoothing Filter-based Modulation (SFIM) brightness temperature estimates had somewhat better performance (RMSEs of ~7 K and an R exceeding 0.9). Although the SFIM had the lowest unbiased RMSE of ~6 K, the effect of cloud cover on Ka-band observations limits data availability.
ABSTRACT
A Neural Network (NN) algorithm was developed to estimate global surface soil moisture for April 2015 to March 2017 with a 2-3 day repeat frequency using passive microwave observations from the Soil Moisture Active Passive (SMAP) satellite, surface soil temperatures from the NASA Goddard Earth Observing System Model version 5 (GEOS-5) land modeling system, and Moderate Resolution Imaging Spectroradiometer-based vegetation water content. The NN was trained on GEOS-5 soil moisture target data, making the NN estimates consistent with the GEOS-5 climatology, such that they may ultimately be assimilated into this model without further bias correction. Evaluated against in situ soil moisture measurements, the average unbiased root mean square error (ubRMSE), correlation and anomaly correlation of the NN retrievals were 0.037 m3m-3, 0.70 and 0.66, respectively, against SMAP core validation site measurements and 0.026 m3m-3, 0.58 and 0.48, respectively, against International Soil Moisture Network (ISMN) measurements. At the core validation sites, the NN retrievals have a significantly higher skill than the GEOS-5 model estimates and a slightly lower correlation skill than the SMAP Level-2 Passive (L2P) product. The feasibility of the NN method was reflected by a lower ubRMSE compared to the L2P retrievals as well as a higher skill when ancillary parameters in physically-based retrievals were uncertain. Against ISMN measurements, the skill of the two retrieval products was more comparable. A triple collocation analysis against Advanced Microwave Scanning Radiometer 2 (AMSR2) and Advanced Scatterometer (ASCAT) soil moisture retrievals showed that the NN and L2P retrieval errors have a similar spatial distribution, but the NN retrieval errors are generally lower in densely vegetated regions and transition zones.
ABSTRACT
SMAP (Soil Moisture Active and Passive) radiometer observations at ~40 km resolution are routinely assimilated into the NASA Catchment Land Surface Model to generate the 9-km SMAP Level-4 Soil Moisture product. This study demonstrates that adding high-resolution radar observations from Sentinel-1 to the SMAP assimilation can increase the spatio-temporal accuracy of soil moisture estimates. Radar observations were assimilated either separately from or simultaneously with radiometer observations. Assimilation impact was assessed by comparing 3-hourly, 9-km surface and root-zone soil moisture simulations with in situ measurements from 9-km SMAP core validation sites and sparse networks, from May 2015 to December 2016. The Sentinel-1 assimilation consistently improved surface soil moisture, whereas root-zone impacts were mostly neutral. Relatively larger improvements were obtained from SMAP assimilation. The joint assimilation of SMAP and Sentinel-1 observations performed best, demonstrating the complementary value of radar and radiometer observations.
ABSTRACT
Two satellites are currently monitoring surface soil moisture (SM) using L-band observations: SMOS (Soil Moisture and Ocean Salinity), a joint ESA (European Space Agency), CNES (Centre national d'études spatiales), and CDTI (the Spanish government agency with responsibility for space) satellite launched on November 2, 2009 and SMAP (Soil Moisture Active Passive), a National Aeronautics and Space Administration (NASA) satellite successfully launched in January 2015. In this study, we used a multilinear regression approach to retrieve SM from SMAP data to create a global dataset of SM, which is consistent with SM data retrieved from SMOS. This was achieved by calibrating coefficients of the regression model using the CATDS (Centre Aval de Traitement des Données) SMOS Level 3 SM and the horizontally and vertically polarized brightness temperatures (TB) at 40° incidence angle, over the 2013 - 2014 period. Next, this model was applied to SMAP L3 TB data from Apr 2015 to Jul 2016. The retrieved SM from SMAP (referred to here as SMAP_Reg) was compared to: (i) the operational SMAP L3 SM (SMAP_SCA), retrieved using the baseline Single Channel retrieval Algorithm (SCA); and (ii) the operational SMOSL3 SM, derived from the multiangular inversion of the L-MEB model (L-MEB algorithm) (SMOSL3). This inter-comparison was made against in situ soil moisture measurements from more than 400 sites spread over the globe, which are used here as a reference soil moisture dataset. The in situ observations were obtained from the International Soil Moisture Network (ISMN; https://ismn.geo.tuwien.ac.at/) in North of America (PBO_H2O, SCAN, SNOTEL, iRON, and USCRN), in Australia (Oznet), Africa (DAHRA), and in Europe (REMEDHUS, SMOSMANIA, FMI, and RSMN). The agreement was analyzed in terms of four classical statistical criteria: Root Mean Squared Error (RMSE), Bias, Unbiased RMSE (UnbRMSE), and correlation coefficient (R). Results of the comparison of these various products with in situ observations show that the performance of both SMAP products i.e. SMAP_SCA and SMAP_Reg is similar and marginally better to that of the SMOSL3 product particularly over the PBO_H2O, SCAN, and USCRN sites. However, SMOSL3 SM was closer to the in situ observations over the DAHRA and Oznet sites. We found that the correlation between all three datasets and in situ measurements is best (R > 0.80) over the Oznet sites and worst (R = 0.58) over the SNOTEL sites for SMAP_SCA and over the DAHRA and SMOSMANIA sites (R= 0.51 and R= 0.45 for SMAP_Reg and SMOSL3, respectively). The Bias values showed that all products are generally dry, except over RSMN, DAHRA, and Oznet (and FMI for SMAP_SCA). Finally, our analysis provided interesting insights that can be useful to improve the consistency between SMAP and SMOS datasets.
ABSTRACT
The goal of this study was to determine the in vivo conditions that promote activation of the (CD4-independent) CD8+ T cell-mediated rejection pathway. We have previously noted that hepatocellular but not islet allografts readily activate this rejection pathway. In the current study, we utilized these two cell transplant models to investigate whether differences in host cell recruitment to the graft site, expression of T-cell activation markers by CD8+ graft infiltrating cells (GICs), and/or development of delayed-type hypersensitivity (DTH) and cytotoxic T lymphocyte cell-mediated effector functions could account for the differential transplant outcomes. The collective results demonstrate that recruitment of CD8+ T cells to the site of transplant, CD103 or CD69 expression on CD8+ GICs, and activation of alloreactive DTH responses are insufficient to initiate CD4-independent, CD8-dependent transplant rejection. Instead, rejection by alloreactive (CD4-independent) CD8+ T cells correlated with expression of CD25, CD154 and CD43 by CD8+ GICs, in vitro alloproliferation by recipient CD8+ T cells, and the development of in vivo allospecific cytolytic effector function. These results suggest that tissue-derived factors influence the activation and maturation of (CD4-independent) CD8+ T cells into cytolytic effectors, which correlates with transplant rejection.
Subject(s)
CD4-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/immunology , Cell Transplantation , Immunity, Cellular , Lymphocyte Activation/physiology , T-Lymphocyte Subsets/immunology , T-Lymphocytes, Cytotoxic/immunology , Animals , Disease Models, Animal , Graft Rejection/immunology , Graft Rejection/pathology , Hepatocytes/transplantation , Islets of Langerhans Transplantation/methods , Mice , Mice, TransgenicABSTRACT
The purpose of this study was to determine if prosody facilitates the comprehension of sentences containing temporary syntactic ambiguities in control, and left (LHD) and right hemisphere damaged (RHD) subjects. To test for effects of prosodic facilitation, sentences were created where prosodic boundaries coincided with (cooperating), were absent (baseline), or conflicted (conflicting) with syntactic boundaries in three response times (RTs) experiments. Despite differences in overall RTs and response accuracy for each group, all three groups responded faster and more accurately to sentences in the cooperating than in the baseline and conflicting conditions across experiments, indicating that prosody facilitates syntactic parsing in brain-damaged subjects just as it does with normal control subjects. Results are discussed in relation to psycholinguistic theories of syntactic parsing and neurolinguistic theories of hemispheric specialization in processing the acoustic properties of prosodic structures.
Subject(s)
Aphasia/physiopathology , Brain/physiopathology , Functional Laterality/physiology , Linguistics , Speech Perception/physiology , Adult , Aged , Aphasia/diagnosis , Female , Humans , Judgment/physiology , Male , Middle Aged , Phonetics , Pilot Projects , Random Allocation , Reaction Time , Severity of Illness IndexABSTRACT
BACKGROUND AND OBJECTIVE: Diabetic patients undergoing cataract surgery have been demonstrated to have a guarded prognosis. Small incision cataract surgery has been postulated to cause fewer complications than other techniques of cataract extraction. We looked at small incision cataract surgery to see how diabetics fared. PATIENTS AND METHODS: One hundred fifty-four eyes of diabetic patients were evaluated preoperatively through dilated fundus examination and Snellen visual acuity. The eyes then underwent small incision cataract surgery and were followed, undergoing periodic ophthalmoscopy, Snellen visual acuity measurement and additional postoperative therapeutic and surgical intervention. RESULTS: Final visual acuity improved by two Snellen lines or more in 61 out of 154 (40%) eyes. Final visual acuity worsened in 38 out of 154 (25%) eyes. CONCLUSIONS: Our results are similar to those reported for extracapsular surgery and phacoemulsification, suggesting that the prognosis is guarded for diabetics, even when undergoing small incision cataract surgery.
Subject(s)
Cataract Extraction/methods , Cataract/complications , Diabetic Retinopathy/complications , Lens Implantation, Intraocular , Adult , Aged , Aged, 80 and over , Diabetic Retinopathy/diagnosis , Diabetic Retinopathy/surgery , Female , Fluorescein Angiography , Follow-Up Studies , Fundus Oculi , Humans , Laser Coagulation , Male , Middle Aged , Minimally Invasive Surgical Procedures , Prognosis , Reoperation , Visual Acuity , VitrectomyABSTRACT
According to Cloninger, three major personality dimensions, novelty seeking, harm avoidance, and reward dependence, are dependent on central monoaminergic systems. This study examined the relationship between the urinary levels of different monoamines and the above personality dimensions. Fifty normal men answered the Tridimensional Personality Questionnaire (TPQ); their levels of dopamine, norepinephrine, epinephrine, normetanephrine, metanephrine, 3-methoxy-4-hydroxyphenylglycol, vanilmandelic acid, homovanilic acid, and serotonin metabolite 5-hydroxyindolacetic acid were measured in urine on two consecutive nights. Significant and positive correlations were found between reward dependence, 3-methoxy-4-hydroxyphenylglycol, and epinephrine (r = .50 and r = .51, respectively). Monoamine levels explained 44% of the variance of reward dependence. Cluster analysis identified three groups of subjects presenting specific patterns of monoamine excretion. The TPQ scores could discriminate among subjects belonging to these clusters. These results point out a narrow relationship between urinary monoamine excretion and the basic personality dimension of reward dependence.
Subject(s)
Biogenic Monoamines/urine , Personality , Reward , Adult , Catecholamines/urine , Cluster Analysis , Humans , Hydroxyindoleacetic Acid/urine , Male , Personality Inventory , Reference ValuesABSTRACT
BACKGROUND AND OBJECTIVE: The goal was to utilize ultrasound-guided cryotherapy as an immediate, low-risk, noninvasive, precise method of treating retinal tears obscured by vitreous hemorrhage. PATIENTS AND METHODS: Eleven patients with sudden onset of vitreous hemorrhage were referred for diagnosis and management. Ophthalmoscopy with scleral depression was unsuccessful at localizing peripheral retinal tears, and all of the patients were examined with ultrasound using the techniques of standardized echography. The cryoprobe was positioned for cryotherapy using both transverse and longitudinal B-scan approaches following the indentation of the globe as it appeared on the oscilloscope. RESULTS: On follow-up examination after the vitreous hemorrhage cleared, 10 of the 11 tears were examined by ophthalmoscopy and were thought to have been adequately treated. One patient had a retinal detachment after remaining stable for 3 months. Two patients were treated with laser to enhance the cryotherapy seal. One patient was observed by another physician and underwent vitrectomy due to vitreous hemorrhage that persisted 2 months following cryotherapy. After vitrectomy, the physician reported a successful cryotherapy reaction at the treated tear. One final patient in the series required vitrectomy and scleral buckle before the hemorrhage had cleared, and the treatment did not appear to be complete. CONCLUSION: Ultrasound-guided cryotherapy provides a noninvasive, inexpensive treatment alternative for retinal tears obscured by vitreous hemorrhage.
Subject(s)
Cryotherapy/methods , Retinal Perforations/diagnostic imaging , Retinal Perforations/therapy , Vitreous Hemorrhage/complications , Aged , Follow-Up Studies , Fundus Oculi , Humans , Male , Middle Aged , Ophthalmoscopy , Retina/diagnostic imaging , Retina/pathology , Retinal Perforations/complications , Retrospective Studies , Ultrasonography , Vitrectomy , Vitreous Body/diagnostic imaging , Vitreous Body/pathology , Vitreous Body/surgery , Vitreous Hemorrhage/diagnosis , Vitreous Hemorrhage/therapyABSTRACT
Free cortisol, luteinizing hormone (LH), total testosterone and monoamines were measured in two successive nocturnal urine collections in 50 healthy men to assess the influence of anticipatory stress. The first collection (N-2) was two nights before and the second (N-1) was just on the night before a one-day experimental stressor consisting of participation in a one-day clinical research protocol. The mean cortisol level increased from 23.4 (N-2) to 66.6 micrograms (N-1), while mean LH level decreased from 2.68 (N-2) to 1.71 IU (N-1) and the mean testosterone level fell from 1.31 (N-2) to 0.70 microgram (N-1). There were no changes in monoamines. Inhibition of sex hormones is a relatively neglected area of stress research.
Subject(s)
Gonadal Steroid Hormones/urine , Stress, Psychological/urine , Adult , Humans , Hydrocortisone/urine , Luteinizing Hormone/urine , Male , Reference Values , Testosterone/urineABSTRACT
Spatial learning in old mice (19 or 24 months old), some of which had been calorically restricted beginning at 14 weeks of age, was compared to that of young mice, in two separate experiments using a Morris water maze. In the first experiment, only old mice reaching criterion performance on a cued learning task were tested in a subsequent spatial task. Thus, all old mice tested for spatial learning had achieved escape latencies equivalent to those of young controls. Despite equivalent swimming speeds, only about half the old mice in each diet group achieved criterion performance in the spatial task. In the second experiment, old and young mice all received the same number of training trials in a cued task and then in a spatial task. Immediately following spatial training, they were given a 60-s probe trial, with no platform in the pool. Both groups of old mice spent significantly less time in the quadrant where the platform had been and made significantly fewer direct crosses over the previous platform location than did the young control group. As in Experiment 1, calorie restriction failed to provide protection against aging-related deficits. However, in both experiments, some individual old mice evidenced performance in spatial learning indistinguishable from that of young controls. Separate comparisons of "age-impaired" and "age-unimpaired" old mice with young controls may facilitate the identification of neurobiological mechanisms underlying age-related cognitive decline.
Subject(s)
Energy Intake/physiology , Maze Learning/physiology , Space Perception/physiology , Aging/psychology , Animals , Cues , Diet , Male , Mice , Mice, Inbred C57BLABSTRACT
The urine of 44 normal men was collected during 2 nights to evaluate components of biological variation, i.e., intraindividual day-to-day variability and interindividual variability in monoamines excretion. Monoamines presented important interindividual variability [interindividual coefficients of variation (%): dopamine 18.3, norepinephrine 66.7, epinephrine 85.3, normetanephrine 22.4, metanephrine 76.8, 3-methoxy-4-hydroxyphenylglycol (MHPG) 77.0, vanilmandelic acid (VMA) 64.3, homovanilic acid (HVA) 71.3, 5-hydroxyindolacetic acid (5-HIAA) 20.4]. The reliability of these amounts was high, with intraclass correlation coefficients ranging from 0.43 (P < 0.001) for MHPG free form to 0.65 (P < 10(-6)) for dopamine and normetanephrine (intraindividual coefficients of variation (%): dopamine 8.5, norepinephrine 39.9, epinephrine 45.9, normetanephrine 10.3, metanephrine 46.3, MHPG 37.5, VMA 30.7, HVA 41.0, 5-HIAA 12.3).
Subject(s)
Dopamine/urine , Epinephrine/urine , Homovanillic Acid/urine , Hydroxyindoleacetic Acid/urine , Methoxyhydroxyphenylglycol/urine , Norepinephrine/urine , Normetanephrine/urine , Vanilmandelic Acid/urine , Adult , Clinical Protocols , Humans , Male , Reproducibility of ResultsABSTRACT
1. Steady-state protein and mRNA levels of the Na+/Ca2+ exchanger were studied in old (24-month) and young (3-month) brains of male Fischer 344 rats by Western and Northern analysis. 2. Northern analysis with a cDNA proble for the Na+/Ca2+ exchanger amplified from human brain RNA indicated the presence of two transcripts for the Na+/Ca2+ exchanger (6 and 16 kb). Both transcripts were present in similar abundance in the cerebrum and hippocampus. In the cerebellum the 6-kb transcript predominated. The cerebellum had the highest overall level of expression. There were no significant age-related effects seen on the level of expression of either transcript in each of the brain areas tested. 3. Western analysis of plasma membrane vesicles purified from cerebral cortex identified a single protein of 116 kDa. Consistent with the Northern analysis, no age-related effect on protein levels was seen. 4. The mechanisms underlying altered Na+/Ca2+ exchange activity in aging rat brain (Michaelis, 1989) most likely do not involve changes in gene expression and are therefore more likely to represent posttranslation modifications of the protein.
Subject(s)
Aging/metabolism , Brain/metabolism , Carrier Proteins/biosynthesis , Gene Expression Regulation, Developmental , Analysis of Variance , Animals , Base Sequence , Blotting, Northern , Blotting, Western , Brain/growth & development , Calcium/metabolism , Carrier Proteins/analysis , Cerebellum/metabolism , DNA Primers , DNA Probes , Hippocampus/metabolism , Humans , Male , Molecular Sequence Data , Polymerase Chain Reaction , RNA, Messenger/analysis , RNA, Messenger/biosynthesis , Rats , Rats, Inbred F344 , Sodium/metabolism , Sodium-Calcium Exchanger , Transcription, GeneticABSTRACT
We have reported a case of colitis cystica profunda, an uncommon, benign disease of the colon presumably due to chronic inflammation, characterized by submucosal mucus-filled cysts. It may be premalignant, having been associated with ulcerative colitis and rectal adenocarcinoma. Diagnosis requires a high degree of suspicion and adequate biopsies, and treatment is by simple excision.
Subject(s)
Colitis/diagnosis , Adult , Colitis/pathology , Colitis/surgery , Humans , Intestinal Mucosa/pathology , Male , Mucocele/pathology , Rectum/pathology , Rectum/surgeryABSTRACT
We recently reported trophic response of transplantable mouse colon cancer cells (MC-26) to pentagastrin, in vivo, and demonstrated gastrin receptors on MC-26 cells, in vitro. In the present study, growth of MC-26 cells in mice, in response to pentagastrin, was studied in relation to binding kinetics and capacity of gastrin receptor. Gastrin receptor levels on mouse fundic and colonic membranes and on MC-26 cellular membranes were determined before MC-26 cell inoculation and designated as Day 0 levels. Four groups of mice were next inoculated with MC-26 cells and given injections of either pentagastrin (treated) or normal saline (control) for 10 or 15 days. At the end of the treatment periods, body, tumor, fundic, and colon weights were noted and gastrin receptor measured. tumor and fundic weights increased significantly within 15 days of pentagastrin treatment, compared to control values. In control (non-pentagastrin treated) mice, the binding affinity of gastrin receptor on tumor membranes was significantly decreased and associated with the complete loss of high-affinity gastrin receptor (Kd = less than 0.5 nM) by Day 15 of tumor growth. On the other hand, both the binding affinity and gastrin receptor levels of tumor membranes were maintained at Day 0 values by pentagastrin treatment. Endogenous gastrin was therefore ineffective in maintaining high-affinity gastrin receptor on control tumors. A significant number of low-affinity gastrin-binding sites (Kd = less than 2 nM) appeared in control tumors by Day 15, which could reflect rapid dedifferentiation or conformational changes of gastrin receptor in the absence of high levels of normal regulatory hormones. These studies demonstrate that the trophic effects of gastrin on MC-26 cells are probably mediated by its regulation and maintenance of the binding affinity and capacity of gastrin receptor on the cancer cells, in vivo.