Otolith-brain stem connectivity: evidence for differential neural activation by vestibular hair cells based on quantification of FOS expression in unilateral labyrinthectomized rats

1. The effects of acute and chronic labyrinthectomies on Fos-defined neuronal activity induced by rotation were determined with the use of quantitative image analysis procedures. Unilateral sodium arsanilate labyrinthectomies (UL) were performed either 24 h (acute) or 2 wk (chronic) before exposure to a 90 min, 2-G centripetal acceleration along the interaural axis that stimulated the intact otolith organs. The results obtained from both acute and chronic UL animals subjected to centripetal acceleration were compared with data obtained from nonrotated UL animals and fully intact, normal animals exposed to centripetal acceleration. Such comparisons allowed the definition of functional projections from the otolith organs of one labyrinth to vestibular related and inferior olivary brain stem nuclei in the rat. 2. The effect of the labyrinthectomy on nonrotated animals was first assessed. After acute UL, asymmetric Fos expression was present in the medial and inferior vestibular nuclei, the prepositus hypoglossi (bilaterally), the ipsilateral (with respect to the side of UL) dorsolateral periaqueductal gray, and the contralateral inferior olivary beta subnucleus, as previously described (Kaufman et al., 1992b). Except for minimal labeling in the contralateral prepositus hypoglossi and the dorsolateral periaqueductal gray, the Fos labeling that was present in the brain stem of acute UL animals was absent in chronic UL animals. Thus Fos neuronal activity appears to define a pattern of brain stem activation associated with the initial events that underlie vestibular compensation. 3. In acute UL rats, which were rotated, the contralateral beta subnucleus of the inferior olive had greater labeling (compared with nonrotated UL animals) when the lesion was away from the axis of rotation. In contrast, the ipsilateral beta subnucleus labeled when the lesion was towards the axis of rotation. Fos expression was observed bilaterally in the prepositus hypoglossi when the lesioned side was oriented toward the axis of rotation but was observed only in the contralateral prepositus nucleus when the lesioned side was oriented away from the axis of rotation. Finally, the dorsomedial cell column of the inferior olive (DMCC) was heavily labeled when the lesioned side was oriented towards the axis of rotation but was unlabeled when the lesioned side was oriented away from the axis of rotation. In acute UL nonrotated animals the DMCC was only lightly labeled. All other brain stem nuclear labeling was similar between the acute UL rotated and nonrotated animals.(ABSTRACT TRUNCATED AT 400 WORDS)

Gravimetric measurements of cerebral edema in a rabbit brain tumor model

The development of tumor-induced cerebral edema was studied in rabbits to establish a data base for future work using this brain tumor model to correlate the degree of edema with other functional and morphological parameters. The VX-2 carcinoma was implanted into the brains of New Zealand White rabbits. Animals were killed 9 and 13 days later, and gravimetric analysis was used to measure the specific gravity of gray and white matter in both the tumor-bearing implanted and contralateral nonimplanted hemispheres. Studies were conducted in untreated tumor-bearing rabbits as well as in those receiving dexamethasone daily for 4 days before death. Tumor tissue and peritumoral gray and white matter and contralateral gray and white matter were analyzed. In all cases, at both 9 and 13 days after tumor cell implantation, tumor tissue exhibited extremely high specific gravity values exceeding the range detectable by the assay procedure. Compared with controls, specific gravity values in tumor-bearing animals generally increased in gray matter and decreased in white matter as a function of tumor growth. This trend was seen in both peritumoral gray and white matter as well as in contralateral gray and white matter areas. However, in most cases, the changes in specific gravity values as compared with controls were not statistically significantly different. The primary exception to this was in peritumoral white matter, in which mean specific gravity values at both 9 and 13 days after implantation were statistically significantly lower than for the corresponding site in control non-tumor-bearing animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Monitoring blood flow to colorectal liver metastases using laser Doppler flowmetry: the effect of angiotensin II

Many colorectal liver metastases are hypovascular, and their low level of perfusion is associated with limited drug uptake and poor response rates with regional chemotherapy. We have previously shown that hepatic arterial vasoconstrictors may increase drug delivery to liver tumours, but the underlying haemodynamic changes have not been defined. Using intraoperative laser Doppler flowmetry (LDF) we have assessed the effect of intraarterial angiotensin II (AI) on tumour blood flow in ten patients with colorectal liver metastases. Measurements were performed during placement of infusion catheters for regional chemotherapy. Blood flow was recorded continuously with a Periflux PF3 perfusion monitor via a probe held on the tumour surface, following hepatic arterial infusion of 15 micrograms AII over 90 s. Six patients with isolated small metastases (< 5 cm in diameter) showed increases in flow, which reached a peak at 170-240 s from the start of AII infusion, and which were closely correlated with the corresponding increase in arterial pressure (r = 0.92, P = 0.009). Of the four patients with large confluent tumour deposits, two showed smaller transient increases in flow over the first 60 s of AII infusion and two had no measurable flow response. Increased blood flow following AII infusion may increase the exposure of tumour to therapeutic agents. This study suggests that both tumour size and the effect upon systemic arterial pressure may be important determinants of the blood flow response to AII. LDF may provide useful information about the potential of AII and other vasoconstrictors to enhance targeting precision.

Fos-defined activity in rat brainstem following centripetal acceleration

To identify rat brainstem nuclei involved in the initial, short-term response to a change in gravito-inertial force, adult Long-Evans rats were rotated in the horizontal plane for 90 min in complete darkness after they were eccentrically positioned off the axis of rotation (off-axis) causing a centripetal acceleration of 2 g. Neural activation was defined by the brainstem distribution of the c-fos primary response gene protein, Fos, using immunohistochemistry. The Fos labeling in off-axis animals was compared with that of control animals who were rotated on the axis of rotation (on-axis) with no centripetal acceleration, or who were restrained but not rotated. In the off-axis animals there was a significant labeling of neurons: in the inferior, medial, and y-group subnuclei of the vestibular complex; in subnuclei of the inferior olive, especially the dorsomedial cell column; in midbrain nuclei, including the interstitial nucleus of Cajal, nucleus of Darkschewitsch, Edinger-Westphal nucleus, and dorsolateral periaqueductal gray; in autonomic centers including the solitary nucleus, area postrema, and locus coeruleus; and in reticular nuclei including the lateral reticular nucleus and the lateral parabrachial nucleus. Also, there was greater Fos expression in the dorsomedial cell column, the principal inferior olive subnuclei, inferior vestibular nucleus, the dorsolateral central gray, and the locus coeruleus in animals who had their heads restrained compared to animals whose heads were not restrained. As one control, the vestibular neuroepithelium was destroyed by injecting sodium arsanilate into the middle ear, bilaterally. This resulted in a complete lack of Fos labeling in the vestibular nuclei and the inferior olive, and a significant reduction in labeling in other nuclei in the off-axis condition, indicating that these nuclei have a significant labyrinth-sensitive component to their Fos labeling. The data indicate that several novel brainstem regions, including the dorsomedial cell column of the inferior olive and the periaqueductal gray, as well as more traditional brainstem nuclei including vestibular and oculomotor related nuclei, respond to otolith activation during a sustained centripetal acceleration.

In vivo evaluation of iophendylate-cyanoacrylate mixtures

Cyanoacrylate glue is a rapidly polymerizing agent used for vascular embolization. Polymerization occurs when the glue comes into contact with ions in the blood or on the vascular endothelium. Mixing iophendylate with cyanoacrylate causes slowing of polymerization, allowing flow-directed embolization into the nidus of an arteriovenous malformation (AVM) or the central neovascularity of a tumor or hemangioma. The authors attempted to define the relationship between the iophendylate-glue ratio and polymerization time with an in vivo swine model. In this model, glue setup occurred much more rapidly than predicted on the basis of in vitro studies. This appeared to be due to glue polymerizing on the endothelium at vessel bifurcations and at areas of acute angulation or marked vessel narrowing. On the basis of these data, the authors substantially increased the iophendylate-glue ratio in their most recent AVM embolization procedures and achieved nidus occlusion in each case. With use of the authors' guidelines, it is possible to achieve optimal distal flow-directed embolization with cyanoacrylate.

Saphenous vein grafts for anatomical variations encountered at surgical insertion of a hepatic artery catheter

Fifty-five consecutive patients, with colorectal metastases confined to the liver, underwent surgical placement of a hepatic artery catheter. At angiography, abnormal hepatic arterial anatomy was present in 33% of patients. In the majority of patients, the hepatic artery catheter was inserted in the conventional manner. In eleven patients with unusual arterial anatomy, a saphenous vein graft was used to create a conduit for the catheter. Satisfactory perfusion was obtained in all patients.

Brainstem Fos expression following acute unilateral labyrinthectomy in the rat

Detection of Fos protein expression with a polyclonal antibody was used to identify brainstem neurons responding to acute (24 h) effects of a unilateral sodium arsanilate chemical labyrinthectomy in Long-Evans rats. Asymmetrical expression was apparent in the medial and inferior vestibular nuclei, the prepositus hypoglossi, the dorsolateral central gray, and the inferior olivary beta subnucleus. These data suggest different distributions of neural activation compared with previous electrophysiological and 2-deoxyglucose results. In addition, there was some Fos expression bilaterally in the olivary dorsomedial cell column, interstitial nucleus of Cajal and the Darkschewitsch nucleus. These results support the concept of multiple systems participating in vestibular compensation and further define some specific nuclei involved in the acute stage.

Glass yttrium-90 microspheres for patients with colorectal liver metastases

Total calculated uniform liver doses of up to 150 Gy were achieved using glass yttrium-90 microspheres administered via the hepatic artery and targeted to tumour using angiotensin II in seven patients with colorectal liver metastases. No toxicity was observed. Hepatic metastatic progression was delayed in six patients. Median survival was 11 months (range 5-25 + months).

Animal rights and research: common sense must prevail

The advances that radiologic science has experienced in recent history have been earned through many means, one of them being animal research. Since the 1980s, animal research has come increasingly into the public eye, through the efforts of animal welfare and animal rights activist groups. These groups, by their varied means, have exacted changes in how animals are used experimentally and how the public perceives such use. In some cases, their lobbying efforts have resulted in laws that raise the cost of research and provide little improvement in animal welfare. Because of the financial and political power of these groups and the increasing public awareness of such issues, it is extremely important that the medical and scientific communities become more involved in educating the public on the importance of animal research and clarifying the difference between animal welfare and animal rights. Equally important, the medical community must continue to adhere to high standards in research that involves animals.

Transient diaphyseal tibial Tc-99m MDP uptake and bone marrow edema in acute rheumatic fever

The authors describe a patient with acute rheumatic fever and polyarthritis in whom scintigraphy unexpectedly identified Tc-99m MDP uptake in the diaphyses of both tibiae. A dramatic rise in antistreptolysin-O titer and rapid resolution of tibial abnormalities paralleled marked articular improvement. Magnetic resonance imaging demonstrated a pattern consistent with marrow edema in the area of abnormal Tc-99m MDP accumulation. This finding has not been previously described in acute rheumatic fever, and it was suspected that the changes in the tibiae resulted from subclinical diaphyseal hyperemia from the inflammatory process observed in the contiguous joints.

Is there a relationship between regional microsphere distribution and hepatic arterial blood flow?

The relationship between hepatic arterial albumin microsphere distribution and hepatic arterial blood flow and the effects of regional angiotensin II were studied in a rat liver metastases model. Hooded-Lister rats were inoculated subcapsularly with 2 x 10(6) HSN sarcoma cells. At 20 days, hepatic arterial blood flow was measured using the reference microsphere technique. Animals then randomly received 50 microliters hepatic arterial saline or albumin microspheres (40 microns, 20 mg ml-1). Hepatic arterial blood flow measurements were then repeated at 5 min. After 5 min, animals were killed and tissues were weighed and counted in a gamma well counter. There were no significant differences between the hepatic blood flow measurements recorded before and after the control hepatic arterial saline infusion. However, regional albumin microspheres produced a significant reduction in tumour and normal liver blood flow and an 80% reduction in mean T/N blood flow ratio. Regional albumin microspheres were delivered to tumour in greater proportions (mean T/N ratio 3.89, SE 0.49) than would be expected from baseline hepatic arterial blood flow (mean T/N ratio 1.28, SE 0.22. P = 0.006). There was no correlation between T/N for baseline blood flow and albumin microsphere distribution.

Diarrhea rates and risk factors for developing chronic diarrhea in infant and juvenile rhesus monkeys

Ten independent risk factors were evaluated in an effort to identify predictors of problem diarrhea at weaning and chronic diarrhea in infant and juvenile rhesus monkeys (Macaca mulatta) at the California Primate Research Center. None of the variables proved to be a significant predictor of problem diarrhea at weaning; however, two of the variables were significant predictors for developing chronic diarrhea. Odds ratios, adjusted for other variables in the logistic regression model, showed that compared with females, males were nearly three times more likely to develop chronic diarrhea, and nursery-reared animals were 7.5 times more likely to develop chronic diarrhea than were breast-fed animals. The annual incidence rates for problem diarrhea at weaning for 1978, 1979, and 1980 were 49%, 37%, and 41%, respectively. A weighted average annual incidence rate for problem diarrhea at weaning for the 3-year period was 39%. The incidence rate for chronic diarrhea for the 3-year period was 49%.

Elective versus emergency surgery for patients with colorectal cancer

A prospective study of 570 patients presenting with colorectal cancer over a 6-year period was undertaken. Of these, 363 were admitted electively and 207 presented as emergencies. The outcome following elective admission was more favourable than after emergency admission. In the elective group the proportion of resected tumours was greater (77 versus 64 per cent, P less than 0.001), the operative mortality rate lower (9 versus 19 per cent, P less than 0.001) and the 5-year disease-related survival rate higher (37 versus 19 per cent, P less than 0.001). These differences may relate to the greater resection rates in the elective situation. Results of surgical intervention might be improved if emergency colorectal operations were undertaken by surgeons with more experience of this type of surgery.

A phase I study of regional 5-fluorouracil and systemic folinic acid for patients with colorectal liver metastases

A phase I study was undertaken in order to establish the maximum tolerated dose of intra-hepatic arterial 5-fluorouracil (5-FU) when given in combination with systemic folinic acid. Patients with colorectal liver metastases (n = 10) received escalating doses of 5-FU as a 24 h infusion with a fixed dose (400 mg m-2) of intravenous folinic acid once per week. Dose limiting toxicity (WHO grade greater than 2) was encountered at 2 g m-2 5-FU. Principal adverse effects were diarrhoea, vomiting and oral ulceration. The recommended dose for phase II studies is 1.5 g m-2 week-1 24 h 5-FU regional infusion with 400 mg m-2 week-1 intravenous folinic acid.

Skeletal lesions and anemia associated with ascorbic acid deficiency in juvenile rhesus macaques

Young rhesus macaques housed in outdoor corn cribs and fed a commercially prepared primate diet became weak, depressed, were reluctant to move, and expressed locomotor abnormalities. Thirteen severely affected animals were hospitalized for evaluation. Physical examination disclosed swellings and instabilities involving the ends of long bones. Radiography confirmed physeal fractures in 11 of 13 animals. Affected bones included the distal femur, proximal humerus, distal tibia/fibula, and distal radius/ulna. Other, less obvious changes were noted on radiographs. Anemia was a consistent finding. Ascorbic acid deficiency was suspected and therapy was initiated that consisted of vitamin supplements, diet change, cage rest, and support bandages. Feed samples were submitted to a laboratory for analysis and were confirmed deficient in vitamin C. Follow-up radiographs showed large calcifying subperiosteal hematomas in epiphyseometaphyseal regions, consistent with a diagnosis of scurvy. Twelve of 13 animals recovered clinically. Subsequent radiographs documented improvement of initially severe angular deformities associated with displaced fractures.

Biosynthetic human proinsulin. Review of chemistry, in vitro and in vivo receptor binding, animal and human pharmacology studies, and clinical trial experience

OBJECTIVE

To describe the rationale for the preclinical and clinical developmental course of human proinsulin (HPI), the second product after human insulin for the treatment of diabetes mellitus to be manufactured by DNA technology.

RESEARCH DESIGN AND METHODS

The relevant and available published and unpublished preclinical and clinical information generated on pork proinsulin and human proinsulin has been integrated to demonstrate how certain clinically attractive features of pork proinsulin (a soluble intermediate-acting and possibly hepatospecific insulin agonist) led to the development of HPI.

RESULTS

Clinical pharmacology studies demonstrated that HPI was definitely, although marginally, hepatospecific. More striking was the finding that the intrasubject/patient coefficient of variation of response to HPI was significantly less than that observed with NPH insulin. However, the fact that unique efficacy in controlled multicenter studies was not demonstrated suggested that these pharmacological features were not translated into clinical benefit. In one multicenter new patient study there were six myocardial infarctions, including two deaths, in patients treated for greater than or equal to 1 yr with HPI and none in the control group.

CONCLUSIONS

To obtain an independent review of the risks and benefits of HPI, in February 1988, Lilly convened a consultant group that examined all relevant information on HPI available. These experts shared our concerns about the safety of HPI in light of the failure to demonstrate unique efficacy. Accordingly, clinical trials with HPI were suspended in February 1988. Experience with HPI demonstrates the challenge associated with the development of new drugs in general and insulin agonists in particular.

A pharmacokinetic comparison of intravenous versus intra-arterial folinic acid

Recent clinical trials have suggested that a combination of folinic acid and 5-fluorouracil (5-FU) may improve response rates and survival in patients with advanced colorectal cancer. However, this regimen has been complicated by potentially life threatening toxicity. Regional delivery of folinic acid via a hepatic artery catheter might be expected to reduce systemic exposure and subsequent adverse effects. The present study compared the pharmacokinetic profiles of intravenous and intra-hepatic arterial infusions of folinic acid in patients with colorectal liver metastases (n = 6) who were being treated with weekly regional infusions of 5-FU. The mean area under the plasma concentration--time curve, the peak plasma concentration and the steady state volume of distribution were 163 micrograms ml-1 h-1 (SD 41), 18.5 micrograms ml-1 (SD 1.2) and 7.41 m-2 (SD 0.44) respectively following intravenous administration of folinic acid compared with 142 micrograms ml-1 h-1 (SD 45), 14.8 micrograms ml-1 (SD 2.4) and 11.21 m-2 (SD 1.22) following intra-hepatic arterial administration (P less than 0.05). Regional folinic acid was therefore associated with a statistically significant reduction in systemic exposure compared with the intravenous route.

Regional delivery of microspheres to liver metastases: the effects of particle size and concentration on intrahepatic distribution

There is increasing interest in the use of microspheres, loaded with chemotherapeutic agents, for regional therapy to hepatic metastases. It is necessary to deliver these particles predominately to tumour rather than to normal liver. This study investigates factors influencing the distribution of regionally injected microspheres. Discreet tumour was induced in rats by subcapsular hepatic inoculations of HSN cells. At 20 days, 12.5 microns, 25 microns or 40 microns diameter, radiolabelled albumin microspheres were administered, in various concentrations, via the gastroduodenal artery. Tumour to normal liver microsphere distribution ratios were determined and median values ranged from 0.1 (0.2 mg ml-1 12.5 microns microspheres) to 1.8 (20 mg ml 40 microns microspheres). Concentrated suspensions (20 mg ml-1) of large microspheres (40 microns) produced the most favourable tumour to normal liver distribution ratios. These results not only have implications for the therapeutic administration of microspheres but also for their use in blood-flow studies.

Activation of a specific vestibulo-olivary pathway by centripetal acceleration in rat

Unanesthetized Long-Evans (pigmented) rats were subjected to 2.0 G centripetal acceleration for 90 min. Immunohistochemical analysis, using a polyclonal antibody for Fos, revealed a distinct pattern of neuronal activation in the off-axis animals in the dorsomedial cell column (DMCC) of the inferior olivary nucleus. These results are consistent with previous anatomical evidence and indicate that the DMCC is an important component in an otolith-olivocerebellar circuit which may help to define an internal spatial reference.

Impact of transfer from animal-source insulins to biosynthetic human insulin (rDNA E coli) in patients with diabetes mellitus

Six hundred forty-eight patients (50.5% men; 49.5% women) with diabetes mellitus on animal-source insulin therapy for at least five years were studied. In this patient population, approximately 68.7% had Type I insulin-dependent diabetes mellitus and 31.3% had Type II noninsulin-dependent diabetes mellitus, nonetheless requiring insulin therapy. Patients were voluntarily transferred from animal-source insulin to biosynthetic human insulin derived by recombinant DNA technology from genetically altered Escherichia coli [human insulin (rDNAE coli)] and were monitored regularly thereafter. At a mean interval of 14 months after transfer to human insulin (rDNAE coli), these patients had gained 0.8 kg in body weight (P less than 0.01). There was a significant decline in systolic (P less than 0.01) but not in diastolic blood pressure. Insulin requirements while on animal-source insulin averaged 47.6 +/- 22.9 U/day (mean +/- SD); this requirement was not significantly different after transfer to human insulin (rDNAE coli) (47.0 +/- 21.2 U/day). The distribution of regular and modified insulin types prescribed did not change after patients were transferred from animal-source insulin to human insulin (rDNAE coli). However, a significant increase in the number of insulin injections from 1.79 +/- 0.59 to 1.96 +/- 0.61 injections/day was observed (P less than 0.001). Fasting glucose levels declined significantly from 202 +/- 87 mg/dl on animal-source insulin to 178 +/- 66 mg/dl on human insulin (rDNAE coli) (P less than 0.001). Postprandial glucose levels (at two hours) also declined from 227 +/- 83 mg/dl to 212 +/- 80 mg/dl. Glycosylated hemoglobin (HbA1c) decreased from 9.57 +/- 2.01% while taking animal insulin to 8.97 +/- 2.00% on human insulin (rDNAE coli) (P less than 0.001) Serum cholesterol and triglyceride levels insulin (rDNAE coli). Serum high-density lipoprotein cholesterol (HDL-cholesterol) levels increased from 54.2 +/- 15.1 mg/dl on animal insulin to 57.2 +/- 15.5 mg/dl on human insulin (rDNAE coli) (P less than 0.001). These data demonstrate that transfer of patients from animal-source insulins to human insulin (rDNAE coli) was associated with: (1) an improvement in glycemic control parameters; (2) a slight increase in the number of insulin injections in some patients, but no overall alteration in insulin requirements; and (3) no adverse trends in indicators of cardiovascular risks, such as serum lipids. Indeed, overall cardiovascular risk may have declined not only as a result of improvement in glycemic control, but also owing to a reduction in systolic blood pressure and an elevation in HDL-cholesterol levels.

Presence of insulin autoantibodies as regular feature of nondiabetic repertoire of immunity

With an ultrasensitive noncompetitive enzyme-linked immunosorbent assay (ELISA), we tested the hypothesis that the presence of insulin autoantibodies in nondiabetic individuals is a normal event. Plasma and peripheral blood mononuclear cells were obtained from 50 nondiabetic whites for determination of insulin autoantibodies by ELISA and radioimmunoassay (anti-insulin IgG [AI-IgG] and 125I-labeled insulin bound [%]), islet cell antibodies, anti-nuclear antibodies and rheumatoid factor, and HLA class II-type antigens (DR, DRw, and DQ). The range of 125I-insulin binding was significantly less than was seen in pretreatment sera from individuals with diabetes (from -0.4 to 0.4% vs. -0.8 to 7.7%, respectively, P = 0.001). Eighty-eight percent of these nondiabetic individuals had significant levels of AI-IgG with preferential binding to human insulin. The geometric mean of AI-IgG concentrations in individuals with significant levels was 180 pM. Binding to human insulin was seen in 88%, to pork insulin in 42%, and to beef insulin in 24% of individuals (P less than 0.001 overall; P less than 0.05 where more bound to pork than beef insulin). Binding of AI-IgG to human insulin-coated plates was substantially inhibited by preincubation with human insulin (median inhibition 57.6%) with little if any inhibition by glucagon, C-peptide, albumin, or IgG. Four individuals had highly specific human AI-IgG as shown by immunoaffinity studies. AI-IgGs were significantly higher in individuals with the HLA haplotype DR4,DRw53,DQ3 and lower in individuals with DR5,DRw52,DQ1 (P = 0.03 for both).(ABSTRACT TRUNCATED AT 250 WORDS)

Transplacental passage of a human relaxin administered to rhesus monkeys

A synthetic version of the human relaxin encoded by the human gene 2 (hR1x-2) was administered to pregnant rhesus monkeys (Macaca mulatta) on gestational days 141-158. Monkeys (three per group) received doses of 100 micrograms/kg or 2000 micrograms/kg as a continuous i.v. infusion over 2 h into a radial vein. One monkey in the low-dose group received, along with the unlabelled hR1x-2, 25.5 microCi/kg of the test material internally labelled with [35S]cysteine. Immunoreactive hR1x-2, as measured by enzyme-linked immunosorbent assay, appeared in all fetuses within 30 min (the first sampling time) of beginning the infusions. Peak fetal plasma levels of hR1x-2 were only 0.8-1.5% of the maternal values. Only 8-15% of the fetal serum radioactivity was hR1x-2. Radioactivity from maternal urine pooled over the 4-h experiment did not elute at the volume corresponding to hR1x-2, but near the column volume.

Changes in the dynamics of the vertical vestibulo-ocular reflex due to linear acceleration in the frontal plane of the cat

The vertical and horizontal components of the vestibulo-ocular reflex (VOR) were recorded in alert, restrained cats who were placed on their sides and subjected to whole-body rotations in the horizontal plane. The head was either on the axis or 45 cm eccentric from the axis rotation. During off-axis rotation there was a change in the linear force acting on the otolith organs due to the presence of a centripetal acceleration along the animal's vertical axis. Otolith forces (defined to be opposite to the centripetal acceleration) directed ventrally with respect to the animal (negative) decreased both the amplitude and time constant of the first-order approximation to the slow phase eye velocity of the vertical vestibulo-ocular reflex (VVOR). Otolith forces directed dorsally (positive) increased the amplitude and time constant. The effects were greater for the up VOR. The asymmetry in the VVOR time constant also depended on the otolith forces, being less in the presence of negative otolith forces that caused the resultant otolith force to move ventrally, towards the direction along which gravity normally acts when the animal is in the upright position. The effects of otolith forces on the up VVOR were independent of whether the animals were tested in the dark or in the light with a stationary visual surround (i.e., during visual suppression). In contrast, the changes in the time constant of the down VVOR were smaller during visual suppression. Simulations of the eye velocity storage mechanism suggest that the gain of the feedback in the storage integrator was modified by the angle between the resultant otolith force and an animal-fixed reference. This could be the animal's vertical, i.e., the direction along which gravity normally acts. For larger angles the feedback was less and the amplitude and time constant of the VVOR increased. The transformation of the otolith input was the same for both the up and down VOR, even though the final effect on the eye velocity was asymmetric (larger for up VOR) due to a separate, asymmetric gain element in the velocity storage feedback pathway.

Regional chemotherapy for inoperable renal carcinoma: a method of targeting therapeutic microspheres to tumour

Regionally-administered, drug-loaded microspheres have a potential role in the treatment of renal tumours. Vasoactive agents, for example, angiotensin II, may allow selective delivery of microspheres to tumour. The present study defines the regional advantage that may be obtained from angiotensin II by quantifying tumour and normal kidney blood flow using radiolabelled microsphere renal perfusion studies and per-operative laser-doppler flow measurements. Angiotensin II increased microsphere distribution to tumour, relative to normal kidney, by a factor of four. This enhancement was associated with an absolute increase in tumour blood flow.