The squirrel monkey as an animal model of pelvic relaxation: an evaluation of a large breeding colony

OBJECTIVE

Findings of pelvic relaxation have been reported in up to 50% of older adult female squirrel monkeys. To evaluate further the potential use of the squirrel monkey as an animal model of pelvic relaxation, we objectively observed and described the perineal findings of 160 adult females. The aim of this study was to examine the relationship of perineal findings to age and parity, factors thought to predispose women to pelvic relaxation.

STUDY DESIGN

The urethra, cervix, and anterior and posterior segments of the vagina were evaluated. The degree of support loss at each site was documented. Genital measurements were obtained by previously reported methods. The findings were tested for association with elements of obstetric history, age, and subspecies.

RESULTS

The females represented three subspecies and ranged from 3 to 17 years old with parities of 0 to 10. The proportion of females with normal support was inversely related to increasing parity and age. Although birth weights, frequency of dystocia at term, and requirement for cesarean section did not differ significantly between females with and without evidence of prolapse, animals with multiple sites of prolapse tended to have infants with higher birth weights. Animals without prolapse were significantly younger and less likely to have been delivered of a term infant (p < 0.001). Subspecies differences unrelated to age or parity were found for each of the genital measurements. Differences were also found between animals with normal perineal findings and those with findings of prolapse. Animals with prolapse had shorter perineal bodies (p < 0.001), greater genital hiatal ratios (p < 0.001), and wider genital hiatal measurements (p < 0.001). Females with abnormal pelvic findings were of increased parity (4.0 vs 1.6, p < 0.001) and age (9.4 vs 6.3 years, p < 0.001) compared with those normal pelvic findings.

CONCLUSION

Analysis of genital prolapse in a large population of breeding squirrel monkeys demonstrated an association of loss of pelvic support with age and parity. A tendency for loss of support at multiple sites was associated with obstetric complications. These observations support continuing investigation into the nature and cause of spontaneous pelvic relaxation in this species and support the potential use of this nonhuman primate as an animal model.

On the correction for radioactive decay in pharmacokinetic modeling

The question of how to include radioactive decay during biological modeling with first-order differential equations was considered. Modeling may involve either experimental data y(t) or decay-corrected data z(t) [identical to exp(lambda t)y(t) where lambda is the decay constant] for each compartment. It is sometimes assumed that the latter are solutions to corresponding purely pharmacokinetic models (no decay). We primarily compared the two analyses in the case where the model did not require simultaneous consideration of both labeled and unlabeled material. A general theorem was found which limits the use of decay-corrected data to pharmacokinetic models containing linear, homogeneous differential equations. By way of verification, an example of this model type was analyzed for a chimeric monoclonal antibody biodistribution in man. Even in this case, statistically significant differences between the two solutions showed that one may find different model parameters depending upon which data set (y or z) was analyzed. For other mathematical forms, the analyst must include the physical decay in all relevant compartments. By analyzing an open, quadratic model, effects of not including decay were seen to be maximized if the biological rate constant was > or = lambda, the physical decay constant. Finally, using monoclonal antibody-antigen reactions, similar discrepancies between the z functions and the pharmacokinetic variables were demonstrated. This result was found to persist even if competitive molecules were included. We conclude that decay-corrected data may be shown, but should not be entered into the modeling equations unless the latter are of the linear, homogeneous form.

Bremsstrahlung radiation dose in yttrium-90 therapy applications

The bremsstrahlung component of the decay scheme of beta emitters has been traditionally ignored in internal dosimetry calculations.

METHODS

We have estimated the radiation dose from the bremsstrahlung component of the decay scheme of 90Y as a function of distance from a point source in a liquid medium and to body organs from distributed sources of 90Y in the liver and spleen.

RESULTS

These estimates agree with measurements of bremsstrahlung dose measured in a Rando phantom, and give an estimate of the importance of this contribution to the overall dosimetry.

CONCLUSIONS

The bremsstrahlung radiation absorbed dose contribution from an organ to itself is very small compared to that from the beta dose, but the contribution to other organs is not always negligible, especially when large amounts of 90Y may be involved, as in therapy applications.

A Study of the Effect of Inhibitors of the Animal Sarcoplasmic/Endoplasmic Reticulum-Type Calcium Pumps on the Primary Ca2+-ATPases of Red Beet

The inhibitor sensitivity of the endoplasmic reticulum (ER) and plasma membrane (PM) calcium pumps of red beet (Beta vulgaris L.) were studied by measuring the ATP-driven accumulation of 45Ca2+ into isolated membrane vesicles. Both transporters were strongly inhibited by 50 [mu]mol m-3 erythrosin B, but only by 50% in the presence of 100 mmol m-3 vanadate. A number of inhibitors considered to be specific for the sarcoplasmic reticulum (SR)/ER-type calcium pump in animal cells were used to further characterize the PM and ER Ca2+-ATPases in red beet and were compared with their effect on the transport and hydrolytic activities of the PM and tonoplast H+-ATPases. The hydroquinones 2,5-di(tert-butyl)-1,4-benzohydroquinone and 2,5-di(tert-amyl)-1,4-benzohydroquinone produced around 20 and 40% inhibition of activity, respectively, of the PM and ER calcium pumps and the PM H+-ATPase when present at concentrations of 30 mmol m-3. In contrast, the vacuolar proton pump displayed a much higher sensitivity to these two compounds. Nonylphenol appeared to have a general inhibitory effect on all four membrane transport proteins and gave almost complete inhibition when present at a concentration of 100 mmol m-3. Thapsigargin and the structurally related compound trilobolide produced 50% inhibition of both the ER and PM calcium pumps at concentrations of 12.5 and 24 mmol m-3, respectively. The PM and tonoplast proton pumps were also sensitive to these compounds. The ER and PM calcium pumps were almost completely insensitive to cyclopiazonic acid (CPA) up to a concentration of 20 mmol m-3. When present at 100 mmol m-3 CPA caused 30% inhibition of the transport properties of all four ATPases. The high concentrations of all of the inhibitors of the SR/ER Ca-ATPase required to inhibit the red beet ER calcium pump, together with the similar effects on the PM calcium pump and the PM and tonoplast proton pumps, suggests that these hydrophobic compounds have a general nonselective action in red beet, possibly through disruption of membrane lipid-protein interactions.

Application of the cross-organ beta dose method for tissue dosimetry in tumor-bearing mice treated with a 90Y-labeled immunoconjugate

BACKGROUND

Radioimmunotherapy of nude mice bearing human tumor xenografts using 90Y-labeled monoclonal antibodies has resulted in slower tumor growth, decreased tumor burden, and increased survival times. Dosimetry estimates in the murine model usually were based on biodistribution data and standard Medical Internal Radiation Dose approaches. A new dosimetric model for the mouse that takes into consideration the small dimensions, mass, and proximity of murine organs has been developed based on self-organ absorbed and cross-organ doses.

METHODS

Nude mice bearing carcinoembryonic antigen-expressing WiDr human colon cancer xenografts were injected with 240 microCi 90Y-anti-carcinoembryonic-antigen monoclonal antibodies and then killed at 12, 24, 72, 120, and 168 hours. Tumors and major organs were removed, weighed, and counted on a gamma counter. Using the resulting biodistribution data, the radiation doses to tumor and normal organs were calculated using the new dosimetric model for the mouse.

RESULTS

Three organs (the liver, kidneys, and large bowel) directly received > 50% of the total absorbed beta dose from radioactivity. Lungs, stomach, and marrow received the highest percentage (70-75%) of the total absorbed dose from adjacent organs. Tumor absorbed dose, estimated with the new dosimetric model, was three times less than that obtained with a MIRD-style calculation without correction for self-absorbed and cross-organ doses.

CONCLUSIONS

The new dosimetric model, which accounts more accurately for self-organ absorbed and cross-organ beta dose fraction, allows the calculation of tumor and organ doses in the murine model. Accurate estimation of radiation doses to tumor and critical organs, such as the marrow, spleen and kidneys, is important in determining the efficacy and toxicity of radioimmunotherapy regimens in animals and in subsequent human applications.

A method including edge effects for the estimation of radioimmunotherapy absorbed doses in the tumor xenograft model

The temporal relationship of radiolabeled monoclonal antibody (Mab) uptake to tumor size in a nude mouse human colon cancer xenograft model (LS174T) was evaluated as an aid to developing a method for estimation of radioimmunotherapy absorbed dose. Tumors of heterogeneous size were treated with 4.4 MBq (120 microCi) of 90Y-labeled anti-Carcinoembryonic Antigen Mab (90Y-ZCE025). Regression analysis demonstrated an inverse log-log relationship of antibody uptake (%ID/g) to tumor mass in four time intervals investigated (N > 10 points/interval):12-24 h, 2-3 d, 5-7 d, and 10-14 d. Curves of predicted radionuclide concentration vs time were then constructed for a range of constant tumor sizes. Xenograft radiation dose was obtained by temporal integration of each curve and application of appropriate dose estimation formulas. For each assumed tumor mass, an edge correction for loss of beta energy outside the target volume was applied assuming a spherical tumor shape. Estimated average absorbed doses were found to vary only from 13.8-10.3 Gy for a 20-fold change in tumor sizes (0.1-2.0 g, respectively). Such constancy of dose may explain xenograft stasis observed by our group in earlier experiments at this level of administered 90Y activity.

A mouse model for calculating cross-organ beta doses from yttrium-90-labeled immunoconjugates

BACKGROUND

The organs of laboratory mice used in radioimmunotherapy experiments are relatively small compared to the ranges of high-energy yttrium-90 (Y-90) beta particles. Current Medical Internal Radiation Dose (MIRD) dosimetry methods do not account for beta energy that escapes an organ. A dosimetry model was developed to provide more realistic dose estimates for organs in mice who received Y-90-labeled antibodies by accounting for physical and geometric factors, loss of beta dose due to small organ sizes, and cross-organ doses.

METHODS

The dimensions, masses, surface areas, and overlapping areas of different organs of 10 athymic nude mice, each weighing approximately 25 g, were measured to form a realistic geometric model. Major organs in this model include the liver, spleen, kidneys, lungs, heart, stomach, small intestine, large intestine, thyroid, pancreas, bone, marrow, and carcass. A subcutaneous tumor mass also was included in the model. By accounting for small organ absorbed fractions and cross-organ beta doses, the MIRD methodology was extended from humans to mice for beta dose calculations.

RESULTS

Absorbed fractions of beta energy were calculated using the Berger's point kernels and the electron transport code EGS4. Except for the tumor and carcass, the self-organ absorbed fractions ranged from 15% to 20% in smaller organs (the marrow and thyroid) to 65%-70% in larger organs (the liver and small intestine). Cross-organ absorbed fractions also were calculated from estimates of the overlapping surface areas between organs.

CONCLUSION

The mathematic mouse model presented here provides more realistic organ dosimetry of radiolabeled monoclonal antibodies in the nude mouse, which should, in turn, contribute to a better understanding of the correlation of biodistribution study results and organ-tumor toxicity information.

Restoration of oocyte maturational competency during the nonbreeding season with follicle-stimulating hormone stimulation in squirrel monkeys (Saimiri boliviensis boliviensis)

The in vitro maturation potential of oocytes retrieved during the nonbreeding season with or without prior in vivo low-dose FSH stimulation was studied in adult squirrel monkeys (Saimiri boliviensis boliviensis). Additionally, the adequacy of various protein supplements in media used for oocyte maturation was investigated. Ovaries were removed from animals in the nonbreeding season (n = 9) with or without prior treatment with a low dose (1 mg) of FSH for four days before ovariectomy. Minimal estradiol elevation was observed in serum even with stimulation. For oocyte collection, ovaries were placed in warmed 21 mM HEPES-buffered Ham's F-10. Oocytes from unstimulated ovaries were retrieved and cultured (47 of 62 recovered) in bicarbonate-buffered Ham's F-10 medium containing 0.5% BSA as protein supplement. Negligible maturation was observed at 48 h (3 of 47; 6%), and no fertilization was seen after insemination. Immature oocytes from animals stimulated with a low dose of FSH were cultured (69 of 94 recovered). With prior FSH stimulation, oocytes placed in 0.5% BSA medium matured (13 of 24; 54%) and fertilized (7 of 21; 33%) in marked contrast to oocytes from the nonstimulated monkeys. Additionally, 20% monkey serum and 20% human follicular fluid were studied as alternative protein supplements for the FSH-pretreated oocytes; these produced similar maturation rates (10 of 22, 45%; 10 of 23, 43%, respectively) and fertilization rates (8 of 21, 38%; 6 of 21, 29%, respectively). In some cases, 2 pronuclei were observed at 16 h and 4 cells were observed at 40 h. Of those activated, 63% showed cleavage ranging from 2 to 8 cells by 96 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Benefits of clinical pharmacy services in a community hospital

The purpose of this analysis was to itemize the long term cost-avoidance and benefits of the Clinical Pharmacy Program at York Hospital and compare them to the cost of the program. It was assumed that the major actual reduction in drug cost would occur within the first year of clinical activities. Therefore, to determine the long term benefits, the hypothetical cost-avoidance of drug expenditures were calculated for the subsequent years after the clinical programs were instituted. For fiscal year 1991 these significant benefits amounted to an estimated monetary cost-avoidance of $416,000, a reduction in numerous hours in preparations and administration of 39,000 IVs, and numerous non-quantifiable benefits. The cost of the program in fiscal year 1991 for the pharmacist and administrative salaries related to the Pharmacy Clinical Program was approximately $140,000. Thus, the Clinical Pharmacy Program was cost-effective at York Hospital.

Pharmacokinetics of an anti-carcinoembryonic antigen monoclonal antibody conjugated to a bifunctional transition metal carborane complex (venus flytrap cluster) in tumor-bearing mice

An anticarcinoembryonic antigen (CEA) monoclonal antibody, T84.66, has been conjugated to a metallocarborane complex (Venus flytrap cluster, VFC) containing 57Co. This radioimmunoconjugate, 57Co-VFC-T84.66, retained > 90% immunoreactivity, was stable in serum (7 days) and demonstrated good localization in LS174T tumor xenografts. Pharmacokinetics of 57Co-VFC-T84.66 in tumor-bearing mice were compared to T84.66 Mab conjugated with either DTPA or its benzylisothiocyanate derivative (BzDTPA) labeled with 111In. Whole-body half-life for VFC-T84.66 was less (t1/2 = 62 hr) than that for either DTPA-T84.66 (t1/2 = 157 hr) or BzDTPA-T84.66 (t1/2 = 167 hr). Blood clearance was similar for all three radioimmunoconjugates (t1/2 = 22 hr). Hepatic uptake of the radiolabel was rapid and remained constant for 7 days for both DTPA radioimmunoconjugates (DTPA radioimmunoconjugate = 13.7 +/- 1.5 %ID/g; BzDTPA radioimmunoconjugate = 10.4 +/- 1.7%ID/g). For VFC, however, liver radioactivity decreased from 19.1 +/- 0.6%ID/g at 1 hr to 0.9 +/- 0.1 %ID/g 7 days postinjection, suggesting a possible role for VFC radioimmunoconjugate in the imaging and therapy of liver metastases.

Considerations on the calibration of small thermoluminescent dosimeters used for measurement of beta particle absorbed doses in liquid environments

An investigation has been carried out on the factors which affect the absolute calibration of thermoluminescent dosimeters (TLDs) used in beta particle absorbed dose evaluations. Four effects on light output (LO) were considered: decay of detector sensitivity with time, finite TLD volume, dose linearity, and energy dependence. Most important of these was the decay of LO with time in culture medium, muscle tissue, and gels. This permanent loss of sensitivity was as large as an order of magnitude over a 21-day interval for the nominally 20-microns-thick disc-shaped CaSO4(Dy) TLDs in gel. Associated leaching of the dosimeter crystals out of the Teflon matrix was observed using scanning electron microscopy. Large channels leading from the outside environment into the TLDs were identified using SEM images. A possibility of batch dependence of fading was indicated. The second most important effect was the apparent reduction of light output due to finite size and increased specific gravity of the dosimeter (volume effect). We estimated this term by calculations as 10% in standard "mini" rods for beta particles from 90Y, but nearly a factor of 3 for 131I beta particles in the same geometry. No significant nonlinearity of the log (light output) with log (absorbed dose) over the range 0.05-20.00 Gy was discovered. Energy dependence of the LO was found to be not detectable, within measurement errors, over the range of 0.60-6.0 MeV mean energy electrons. With careful understanding of these effects, calibration via gel phantom would appear to be an acceptable strategy for mini TLDs used in beta absorbed dose evaluations in media.(ABSTRACT TRUNCATED AT 250 WORDS)

Investigation of the Calcium-Transporting ATPases at the Endoplasmic Reticulum and Plasma Membrane of Red Beet (Beta vulgaris)

Calcium-transporting ATPases were compared in endoplasmic reticulum (ER)- and plasma membrane-enriched fractions of red beet (Beta vulgaris L.) storage tissue by measuring 45Ca uptake and calcium-dependent phosphoenzyme formation. The plasma membrane fraction was prepared by aqueous two-phase partitioning of a microsomal fraction and collecting the upper phase. The ER-enriched fraction was obtained by submitting a sucrose-gradient ER-enriched fraction to aqueous two-phase partitioning and collecting the lower phase; this reduced contaminating plasma membrane, which partitioned into the upper phase. The ATP-dependent calcium uptake observed in both fractions was released by the calcium ionophore A23187. Calcium uptake showed saturation kinetics for calcium with Km values of 0.92 mmol m-3 for the ER fraction and 1.24 mmol m-3 for the plasma membrane fraction. Uptake into both fractions was inhibited by vanadate and erythrosin B, although the plasma membrane system was slightly more sensitive to both inhibitors. Cyclopiazonic acid and thapsigargin, at low concentrations, had no marked effect on uptake. The plasma membrane system was less substrate-specific for ATP than the ER system, since it was able to use GTP and ITP to drive calcium transport at up to 50% of the level obtained with ATP. Following phosphorylation with [[gamma]-32P]ATP, two high molecular mass, calcium-dependent phosphoproteins (119 and 124 kD) and a low molecular mass, calcium-independent phosphoprotein (17 kD) were observed in the plasma membrane fraction. The ER fraction showed one high molecular mass phosphoprotein (119 kD) in the presence of calcium and two low molecular mass phosphoproteins (17 and 20 kD) that showed no calcium dependence. The low molecular mass phosphoproteins were insensitive to hydroxyl-amine, but they did show turnover. The identity of these proteins is unknown, but they do not have the properties of phosphorylated intermediates of calcium-ATPases. In contrast, the high molecular mass phosphoproteins displayed properties consistent with their representing phosphorylated intermediates of E1E2-type ATPases; they were hydroxylamine-sensitive, showed rapid turnover, and were inhibited by vanadate. Because they showed calcium-dependent phosphorylation and were sensitive to erythrosin B, the 119- and 124-kD phosphoproteins may be phosphorylated intermediates of the ER and plasma membrane calcium ATPases. These phosphoproteins were characterized further with respect to inhibitor sensitivity, responses to ions, and substrate specificity.

Uptake of radiolabeled anti-CEA antibodies in human colorectal primary tumors as a function of tumor mass

An inverse correlation has been demonstrated between tumor uptake (u, in units of % injected dose/kg) of monoclonal antibody (Mab) and tumor mass (m, in units of g) for colorectal carcinoma in a series of 19 consecutive patients. The correlation (rho = -0.510), developed using surgical samples was of the form u = amb and was significant at the 2% level of confidence. All tumors were positive for carcinoembryonic antigen (CEA) and the radiopharmaceutical was an iodine-131 labeled anti-CEA Mab. Such correlations have been predicted earlier from murine and rat tumor uptake data. The slope parameter (b) was -0.362, a number consistent with the previous value (-0.382) found in anti-CEA experiments in mice bearing human xenograft LS174T tumors.

Dosimetry of solid tumors

Dosimetry data arising from a decade of radioimmunotherapy are summarized along with techniques utilized to arrive at the reported dose estimates. Generality of the MIRD methodology allows it to serve as a vehicle for the calculation of solid tumor dosimetry although several limitations exist. Nonstandard geometries of solid tumors will ultimately necessitate determination of absorbed fractions for the individual tumors. Several approaches currently under investigation are described. For reasons of practicality, solid tumor dosimetry estimates continue to use the assumption of homogeneous activity distribution in a source organ, accounting for either all radiation or only nonpenetrating radiation. As computation tools become available for incorporating inhomogeneous cellular level data, the currently used "average dose" as an index of tumor sterilization will likely be replaced with a statistical distribution based on the number of viable cells in the tumor volume. Estimates of a tumor control dose would be based upon a linear extension of dose coupled with a threshold dose for cell sterilization.

Multicellular dosimetry for beta-emitting radionuclides: autoradiography, thermoluminescent dosimetry and three-dimensional dose calculations

Inhomogeneities in activity distributions over distances from 10 to 10(4) microns are observed in many tumors treated with radiolabeled antibodies. Resulting nonuniformities in absorbed dose may have consequences for the efficacy of radioimmunotherapy. Activity variations may be directly studied with quantitative autoradiography (ARG). Converting these data to absorbed dose distributions requires additional information about pharmacokinetics, the use of a point source function and consideration of the complete three-dimensional activity distribution, as obtained from sequential autoradiographic slices. Thermoluminescent dosimetry with specially prepared CaSO4:Dy dosimeters implanted into tissue can directly measure absorbed dose in selected regions. The conditions under which thermoluminescent dosimeters (TLD) are used differ markedly from "normal" use conditions in external beam radiotherapy. Therefore special calibration and quality assurance precautions are needed to assure the precision of this technique. Procedures and pitfalls in the use of both techniques in radioimmunotherapy are described.

Comparison of radioimmunotherapy and external beam radiotherapy in colon cancer xenografts

Radioimmunotherapy and external beam radiotherapy were compared in a nude mouse human colon cancer model. Radioimmunotherapy was delivered by intraperitoneal injection of 90Y-labeled anticarcinoembryonic antigen monoclonal antibody (anti-CEA MAB). Single fraction external beam radiotherapy was delivered using a 60Co teletherapy unit. Control groups received saline, unlabeled anti-CEA monoclonal antibody and labeled nonspecific monoclonal antibody. Subcutaneous CEA-expressing LS174T human colon carcinoma tumors were measured over time. Tumor growth suppression was expressed as delay to reach 2g compared to saline controls. Unlabeled anti-CEA monoclonal antibody and labeled nonspecific monoclonal antibody had no effect. External beam radiotherapy of 300, 600, 1000 and 2000 cGy produced growth delays of 3, 12, 17, and 22 days, respectively. Radioimmunotherapy with 120 microCi, 175 microCi, and 225 microCi resulted in growth delays of 20, 34, and 36 days. Estimated absorbed tumor dose was 1750 cGy in the 120 microCi group. Similar comparisons were done with the more radioresistant WiDr human colon carcinoma cell line. External beam radiotherapy doses of 400, 800, 1200, and 1600 cGy resulted in growth delays of 6, 21, 36 and 48 days, respectively. Radioimmunotherapy of 120 microCi and 175 microCi resulted in growth delays of 9 and 19 days, respectively. The 120 microCi dose delivered an estimated absorbed tumor dose of 1080 cGy to WiDr tumors. In summary, for the radiosensitive LS174T line, radioimmunotherapy produced biologic effects that were comparable to a similar dose of single fraction external beam radiotherapy. For the more radioresistant WiDr tumor, radioimmunotherapy produced a biologic effect which was less than a similar dose of single fraction external beam radiotherapy. These studies suggest that a tumor's response to radioimmunotherapy relative to that of external beam radiotherapy is, in part, dependent on tumor radiosensitivity and repair capacity.

Origin of urinary epidermal growth factor in humans: excretion of endogenous EGF and infused [131I]-human EGF and kidney histochemistry

1. This study examined (i) whether blood-infused epidermal growth factor (EGF) can pass into urine; (ii) whether infused labelled EGF behaves like endogenous plasma immunoreactive EGF; and (iii) which parts of the human nephron show morphological evidence of EGF synthesis? 2. We infused human [131I]-EGF into a volunteer. After 6 min, only 66% of the plasma counts represented intact EGF. At the end of infusion, the T1/2 of EGF was calculated to be 1.6 min. The tail of the curve lasted for at least another 2 h. The total excretion of the labelled EGF was 2.45% of the infused dose and was proportional to the urine volume. 3. After a water load, the excretion of endogenous EGF was, on the contrary, inversely related to urine volume. 4. Immunohistochemically, human kidneys were not stained by monoclonal anti-EGF antibodies but showed positive in situ hybridization for EGF mRNA in the nuclei of glomerular mesangial cells, distal convoluted tubules and collecting tubules. 5. We conclude that human kidneys synthesize EGF and release it into urine. Plasma-derived EGF constitutes under normal conditions only a small part of the urinary EGF. Contrasting volume-dependency of the excretion of endogenous and [131I]-EGF requires further study and cautions against extrapolating results obtained with labelled EGF to physiological conditions.

A technical analysis of an intraoperative radiation detection probe

A technical evaluation was made of a commercial intraoperative radiation probe. This device utilizes a CsI (T1) scintillation detector and light pipe arrangement to count gamma radiation in vivo. After determining the optimal window and threshold setting, additional evaluations included linearity, distance response function, detector dead time, counter reproducibility, detector sensitivity, angular resolution, and energy resolution. Detector dead time (21.2 microseconds) was found to be characteristic of a nonparalysable system. Activity response for each radionuclide was linear (R = 0.99) both with and without collimation. Energy resolution, 25% at 210 keV, was not sufficient to separate the two photons (172 and 247 keV) emitted by 111In. Detector sensitivity was 1136 and 626 counts per s per microcurie of 111In and 99mTc, respectively. The mean effective distance from the face of the uncollimated probe to the crystal was determined to be 2.03 cm in air.

An immunoradiometric assay for squirrel monkey prolactin

Determination of immunoreactive prolactin in squirrel monkeys has been hampered by the lack of specific antibodies. We investigated the adaptability of a commercially available immunoradiometric assay for human prolactin, which employs two separate monoclonal antibodies (MAb I and II) to human prolactin, to determine the presence of squirrel monkey prolactin. We found that immunoreactivity curves for prolactin in squirrel monkey pituitary homogenates and serum were parallel to human prolactin standards, suggesting that the epitopes recognized by these antibodies were common to both human and squirrel monkey prolactin. Both nonglycosylated (23 kD) and glycosylated (26 kD) forms of squirrel monkey prolactin were detected in squirrel monkey pituitary homogenates by Western blot analysis using [125I]-MAb II. Neither sheep nor rat prolactin was recognized by Western blot analysis, indicating that the assay may be specific for primate prolactins. We examined the effect of ketamine HCl, an anesthetic that has been shown to elevate serum prolactin levels in other primates, on prolactin secretion in squirrel monkeys. Serum prolactin levels increased greater than fourfold after the administration of ketamine HCl (30 mg/kg b.w., i.m.) compared with control levels. Serum prolactin levels were unaffected by anesthesia with pentobarbital sodium (15 mg/kg b.w., i.v.). This assay provides a reliable and sensitive method for determining immunoreactive squirrel monkey prolactin.

Gamma-interferon enhancement of carcinoembryonic antigen expression in human colon carcinoma xenografts

Athymic nu/nu mice bearing a subcutaneous human colon cancer xenograft (WiDr, low CEA expression) were treated with gamma-interferon (gamma IFN) at varying doses, frequencies, and periods of duration. CEA content (micrograms/g) and uptake of radiolabeled anti-CEA monoclonal antibody (MAB) (percent injected dose per gram, % ID/g) were measured at 48 h following administration of the MAB, The optimal enhancement of tumor CEA content and tumor localization of [111In] anti-CEA monoclonal antibody (MAB) was seen at gamma IFN doses of 100,000 U i.p. every 8 h for 4 days (4.7 micrograms/g; 29% ID/g) compared to control animals (0.9 micrograms/g; 10% ID/g). The effects of gamma IFN on CEA content and MAB localization were less pronounced when administered (a) at lower doses: 5,000 to 50,000 U i.p. every 8 h, (b) at varying frequencies: 300,000 U/day delivered in divided doses every 4 or 24 h, or (c) for varying periods: 2 or 6 days of therapy. In each case, the biologic effects on tumor CEA content and uptake of [111In]MAB correlated closely with the serum gamma IFN level. Therefore, we conclude that enhancement of in vivo CEA expression by gamma IFN may have clinical relevance for tumor imaging and therapy using radiolabeled monoclonal antibodies.

Characterization of solute/proton cotransport in plasma membrane vesicles from Ricinus cotyledons, and a comparison with other tissues

Plasma membrane vesicles, purified by aqueous two-phase partitioning, were used to investigate the presence of sugar and amino acid carriers in cotyledons and roots of Ricinus communis L. and in roots of red beet (Beta vulgaris L.). Artificial pH and electrical gradients were generated across the plasma membrane, and [(14)C]acetate and [(14)C]tetraphenylphosphonium were used to demonstrate the presence of an internal alkaline pH gradient and an internal negative membrane potential, respectively. In Ricinus cotyledons, uptake of sucrose was more strongly inhibited than that of glutamine by p-chloromercuribenzenesulphonic acid, phlorizin and phenylglyoxal. The sucrose transport system showed a high degree of substrate specificity with only the presence of maltose and phenyl-α-glucoside significantly affecting sucrose uptake; in contrast, the glutamine transport system was inhibited by a number of other amino acids. ΔpH+gDψ-driven glutamine uptake showed saturation kinetics with a K m of 0.35 mol · m(-3). Sucrose and glutamine Δψ-driven uptake was pH dependent with an optimum in the acidic range (pH 6.25) and a decrease at higher pH values. Vesicles obtained from cotyledons and roots of Ricinus showed different transport properties. In the cotyledons, gDH+gDψ-driven transport for both sucrose and glutamine were observed at similar levels; however, in the root tissue, δpH-Δψ-driven glutamine transport was the dominant uptake process. Uptake rates for glucose and fructose were low in the cotyledons whereas, in the roots, glucose and sucrose transport were slightly higher than that of fructose. In vesicles from red beet tissue there was a different uptake profile, with evidence of proton-coupled cotransport systems for sucrose and glucose, but lower uptake of glutamine and fructose. The results are discussed in relation to the reported different pathways for loading and unloading of solutes in these tissues.

Developmental changes in ECG associated with heart rate are similar in squirrel monkey and human infants

Interest in refining noninvasive methods of diagnosis and further characterization of squirrel monkeys (Saimiri sp.) as a model for pediatric cardiology studies led to this investigation of electrocardiogram (ECG) changes associated with changes in age and position. During a single delivery season, ECGs were performed at 1 day, 1 month, and 1 year of age. For each age group, ECGs were recorded with animals in dorsal, ventral, and right lateral recumbency. The 1-day-old group had the lowest heart rates (271 +/- 10, right lateral recumbency, mean +/- SEM) relative to the other age groups. One-year-old monkeys had heart rates of 333 +/- 18. One-month-old infants had rates significantly higher than the other two age groups (366 +/- 4). The QRS frontal-plane axis showed an age-related leftward change from 1 day (151 +/- 28 degrees) to 1 year of age (121 +/- 44 degrees) while the P-wave frontal plane axis remained nearly constant over a narrow range at all ages. The pattern of heart rate changes with age were similar to those in humans, although the ranges of absolute heart rates were markedly different. These data suggest that factors that influence maturational changes in heart rate, conduction time (as reflected by ECG intervals) and cardiac chamber size and position (inferred from axis and voltage) are similar among primates of widely variant body sizes.