Effect of a longitudinal course on student performance in clerkships

OBJECTIVE

To determine the effect that a 3-year primary-care course experience with family medicine, internal medicine, or pediatric preceptors would have on clerkship performance in pediatrics and internal medicine.

DESIGN

In 1 academic year, third-year students were divided retrospectively into 3 groups based on preceptor type in the primary care course. An analysis of variance was conducted. When the analysis of variance showed statistical significance, a multiple-comparison t test was performed.

SETTING

University medical school with a longitudinal preceptor experience.

PARTICIPANTS

One hundred nine third-year medical students who participated in the primary care course and completed the pediatric and internal medicine clerkships. Fifty-six students took part in the self-assessment portion of the study.

MAIN OUTCOME MEASURES

Student performance scores in the pediatric clerkship and internal medicine clerkship were analyzed for significant differences based on preceptor type. Student self-assessment on pediatric objectives was analyzed for significant differences based on preceptor experience.

RESULTS

Students with pediatric preceptors received higher clinical scores in the pediatric clerkship (P = .04) and perceived themselves as more advanced on 18 of the 39 pediatric curriculum pretest self-assessment items. Students with pediatric or internal medicine preceptors received significantly higher scores on the written patient medical history and physical examinations (P = .02). There were no significant differences on the pediatric written examination. There were no significant performance differences in the internal medicine clerkship. All hypothesis testing was conducted at the 95% confidence level.

CONCLUSION

Experiences with pediatric preceptors in the early years of medical school may improve a student's performance and confidence in the pediatric clerkship.

Brugia pahangi: quantitative analysis of infection in several inbred rat strains

We report a comprehensive study of the infectivity of Brugia pahangi in male and female rats of eight different inbred strains. A single infection of any inbred rat strain will produce rats that become microfilaremic, have occult infection, or clear the primary infection. The proportion belonging to any category is determined by the basic susceptibility level of that strain. Patency rates (blood microfilaria+) ranged from 24% (AO rats) to 73% (WKA rats). The period for which microfilaria were in the circulation was directly related to microfilarial burden, with rats carrying less than 50 mf/ml of blood patent for 11.8 weeks +/- 12.2; for 50-499 mf/ml it was 37.6 +/- 14.8 and for 500+ mf/ml it was 63.3 +/- 34.2 weeks. Suckling rats were resistant to infection (0 patent) and weanlings were intermediate in resistance between suckling and adult rats. Female rats were highly resistant to infection. Approximately half of amicrofilaremic rats have occult infections. A high proportion of patent infections involve the testes or testicular lymphatics. In the most susceptible rat strains, more than 95% of the administered L3 or developing L4 parasites were killed within 28 days. During the course of the first 6 months, the ratio of males to females fell significantly, suggesting a shorter life span in male worms. The features of the infectivity/patency patterns in rats are compared with recognized patterns obtaining in human populations. We conclude that rats provide a valuable and underutilized model for the experimental analysis of filarial infections.

Cortical and subcortical control of tongue movement in humans: a functional neuroimaging study using fMRI

We have used voluntary tongue contraction to test whether we can image activation of the hypoglossal nuclei within the human brain stem by using functional magnetic resonance imaging (fMRI). Functional images of the whole brain were acquired in eight subjects by using T2-weighted echo planar imaging (blood oxygen level development) every 6.2 s. Sequences of images were acquired during 12 periods of 31-s "isometric" rhythmic tongue contraction alternated with 12 periods of 31-s tongue relaxation. Noise arising from cardiac- and respiratory-related movement was removed either by filtration (high pass; cutoff 120 s) or by inclusion in the statistical analysis as confounding effects of no interest. For the group, tongue contraction was associated with significant signal increases (P < 0.05 corrected for multiple comparisons) in the sensorimotor cortex, supplementary motor area, operculum, insula, thalamus, and cerebellum. For the group and for six of eight individuals, significant signal increases were also seen within the medulla (P < 0.001, predefined region of interest with no correction for multiple comparisons); this signal is most likely to reflect neuronal activation associated with the hypoglossal motor nuclei. The data demonstrate that fMRI can be used to detect, simultaneously, the cerebral and brain stem control of tongue movement.

Primary-care delivery for sickle cell patients in rural Georgia using telemedicine

BACKGROUND

Advances in newborn screening and pediatric management of sickle cell disease have resulted in patients living well into adulthood. For adults, preventive care and medication monitoring are crucial for optimal health maintenance. The Medical College of Georgia (MCG) in Augusta provides consultative services and comprehensive medical care to about 1200 sickle cell patients residing in middle and southern Georgia. An increase in the demand for clinical services in this patient population has resulted in expansion of sickle cell outreach efforts throughout the state.

OBJECTIVE

A telemedicine clinic for adult sickle cell patients was established in order to meet the growing clinical demands.

METHODS

An on-site outreach clinic was introduced in the target area. After 10 months of operation, a monthly telemedicine clinic was offered to patients as an option for routine medical follow-up. A clinic model was used, with scheduled appointments and a public health nurse assisting at the remote site. Phlebotomy and laboratory services enhanced the telemedicine encounter.

RESULTS

Over a 12-month period, 52 encounters for 28 patients from 17 medically underserved counties were completed. All patients were African-American, and 89. 3% had Medicaid or Medicare insurance coverage or both. The clinic encounter time was 24 +/- 7.9 minutes (mean +/- SD), comparable to that for all telemedicine clinic encounters during the same period.

CONCLUSIONS

The adult sickle cell population in rural Georgia accepts innovative health care delivery using telemedicine. Thus, the telemedicine sickle cell clinic has increased access to care for rural patients in underserved areas. For providers, it has allowed greater clinical productivity and diminished travel time to outreach clinics.

External thoracic restriction, respiratory sensation, and ventilation during exercise in men

Multiple factors may contribute to the dyspnea associated with restrictive ventilatory disease (RVD). Simple models that examine specific features of this problem are likely to provide insight into the mechanisms. Previous models of RVD utilizing elastic loads may not represent completely the impact on pulmonary and chest wall receptors derived from breathing at low thoracic volumes. The purpose of this study was to investigate the sensory consequences of breathing at low lung volumes induced by external thoracic restriction in an attempt to further elucidate the etiology of dyspnea in this setting. Ten men were studied, with and without an inelastic corset applied at residual volume (restriction resulted in mean reductions in vital capacity, functional residual capacity, residual volume, and forced expired volume in 1 s of 44, 31, 12.5, and 42%, respectively). During 10-min steady-state exercise tests (at a workload set to achieve approximately 65% maximum heart rate), restriction resulted in significant increases, compared with control, in minute ventilation (61 vs. 49 l/min), respiratory frequency (43 vs. 23 breaths/min), and visual analog scale measurements of respiratory discomfort (65 vs. 20 mm). Alveolar hyperventilation (end-tidal PCO2 = 39 vs. 44 Torr for control) and mild O2 desaturation (arterial blood O2 saturation = 93 vs. 95% for control) occurred. Hypoxemia, atelectasis, increased work and effort of breathing, or a decrease in the volume-related feedback from chest wall and/or lungs could be responsible for the increased dyspnea reported. External thoracic restriction provides a useful model to study mechanisms of dyspnea in RVD.

Metabolic activation of racemic and enantiomeric trans-8, 9-dihydroxy-8,9-dihydrodibenzo[a,l]pyrene (dibenzo[def,p]chrysene) to dibenzo[a,l]pyrene-bis-dihydrodiols by induced rat liver microsomes and a recombinant human P450 1A1 system: the role of the K-region-derived metabolic intermediates in the formation of dibenzo[a,l]pyrene-DNA adducts

Metabolic activation studies of dibenzo[a,l]pyrene (DB[a,l]P) (dibenzo[def,p]chrysene), an extremely potent environmental carcinogen, have been focused on metabolism at the fjord region, a region associated with high mutagenic and carcinogenic activities of the corresponding fjord-region DB[a,l]P-11,12-diol-13,14-epoxides. DB[a,l]P is metabolized by beta-naphthoflavone (BNF)- and 3-methylcholanthrene-induced rat liver microsomes and a recombinant human P450 1A1 system to two major dihydrodiols, the K-region dihydrodiol, DB[a,l]P-8,9-dihydrodiol (DB[a,l]P-8,9-diol), and the fjord-region dihydrodiol, DB[a,l]P-11,12-dihydrodiol. We have investigated the further metabolic activation of DB[a,l]P-8,9-diol by BNF-induced rat liver microsomes and a recombinant human P450 1A1 system with epoxide hydrolase to DB[a,l]P-bis-diols and to DNA adducts. (+/-)-trans-DB[a,l]P-8,9-diol was synthesized and resolved into its enantiomers. Racemic trans-DB[a,l]P-8,9-diol was metabolized by BNF-induced rat liver microsomes to six metabolites: two diastereomers of trans,trans-DB[a,l]P-8,9:11,12-bis-diol, two diastereomers of trans,cis-DB[a,l]P-8,9:11,12-bis-diol, and two diastereomers of trans-DB[a,l]P-8,9:13,14-bis-diol as characterized by NMR, MS, and UV spectroscopy. Metabolic studies using both enantiomeric (-)- and (+)-trans-DB[a,l]P-8,9-diol further demonstrated that each diastereomer of trans,trans-DB[a,l]P-8,9:11, 12-bis-diol and trans-DB[a,l]P-8,9:13,14-bis-diol was comprised of two enantiomers. Similarly, incubations of enantiomeric or racemic trans-DB[a,l]P-8,9-diol with a recombinant human P450 1A1 system and epoxide hydrolase also gave the same two enantiomeric mixtures of diastereomers of trans,trans-DB[a,l]P-8,9:11,12-bis-diol and the same two enantiomeric mixtures of diastereomers of trans-DB[a,l]P-8, 9:13,14-bis-diol. This suggested that the microsomal oxidations of (-)- and (+)-trans-DB[a,l]P-8,9-diol were stereospecific. The stereospecific formation of enantiomers of trans-DB[a,l]P-8,9-diol from DB[a,l]P was examined using both BNF-induced rat liver microsomes and a recombinant human P450 1A1 system with epoxide hydrolase. Stereospecificity was observed as both metabolic systems favored the formation of (-)-trans-DB[a,l]P-8,9-diol by 8-9-fold. DNA adduct studies were undertaken using TLC/HPLC 32P-postlabeling techniques. In the presence of a recombinant human P450 1A1 system with epoxide hydrolase, DB[a,l]P gave two groups of calf thymus DNA adducts. The group of later-eluting adducts were identified as arising from syn- and anti-DB[a,l]P-11,12-diol-13,14-epoxides, while the more polar early-eluting adducts were derived, in part, from the further activation of trans-DB[a,l]P-8,9-diol. Our data indicate that, in P450 1A1-mediated microsomal incubations, DB[a,l]P is metabolized to trans-DB[a,l]P-8,9-diol which is further metabolized to DB[a,l]P-bis-diols. trans-DB[a,l]P-8,9-diol is metabolically activated to intermediates that can bind to DNA and give DNA adducts similar to those observed with DB[a,l]P. These results indicate that DB[a,l]P can be metabolically activated by both fjord-region and K-region pathways.

Serum biochemistry of captive and free-ranging gray wolves (Canis lupus)

Normal serum biochemistry values are frequently obtained from studies of captive sedentary (zoo) or free-ranging (wild) animals. It is frequently assumed that values obtained from these two populations are directly referable to each other. We tested this assumption using 20 captive gray wolves (Canis lupus) in Minnesota, USA, and 11 free-ranging gray wolves in Alaska, USA. Free-ranging wolves had significantly (P < 0.05) lower sodium, chloride, and creatinine concentrations and significantly higher potassium and blood urea nitrogen (BUN) concentrations; BUN to creatinine ratios; and alanine aminotransferase, aspartate aminotransferase, and creatine kinase activities relative to captive wolves. Corticosteroid-induced alkaline phosphatase activity (a marker of stress in domestic dogs) was detected in 3 of 11 free-ranging wolves and in 0 of 20 captive wolves (P = 0.037). This study provides clear evidence that serum biochemical differences can exist between captive and free-ranging populations of one species. Accordingly, evaluation of the health status of an animal should incorporate an understanding of the potential confounding effect that nutrition, activity level, and environmental stress could have on the factor(s) being measured.

Experience with a new multifunctional articulated instrument holder in minimally invasive navigated neurosurgery

A new multifunctional articulated instrument holder for use in minimally invasive navigated neurosurgery is presented. The instrument holder is secured to the Mayfield clamp, yielding permanent fixation and guidance of instruments. Thus, surgical conditions with the advantages of both conventional and frameless stereotaxic neurosurgery are created without sacrificing the relevant advantages of both methods. Accuracy testing of the instrument holder in combination with the neuronavigation system EasyGuide Neuro demonstrated an error of 0.0 to 2.4 (mean 1.6) mm. In clinical testing, the device has been used for guided catheter insertions, pointer fixation for continuous intraoperative guidance and trajectory planning, navigated endoscopic procedures, and navigated intracerebral biopsies in totally 53 patients.

Electrocardiographic consequences of a peripatetic lifestyle in gray wolves (Canis lupus)

Cardiac chamber enlargement and hypertrophy are normal physiologic responses to repetitive endurance exercise activity in human beings and domestic dogs. Whether similar changes occur in wild animals as a consequence of increased activity is unknown. We found that free-ranging gray wolves (Canis lupus, n = 11), the archetypical endurance athlete, have electrocardiographic evidence of cardiac chamber enlargement and hypertrophy relative to sedentary captive gray wolves (n = 20), as demonstrated by significant increases in QRS duration, QT interval, and QT interval corrected for heart rate, a tendency towards increased Q, R, and S wave voltages in all leads, and a significant decrease in heart rate. We conclude that exercise activity level and therefore lifestyle affects physiologic variables in wild animals. An immediate consequence of this finding is that physiologic measurements obtained from a captive wild-animal population with reduced exercise activity level may not accurately reflect the normal physiologic state for free-ranging members of the same species.

Role for calcium from the sarcoplasmic reticulum in coupling muscle activity to nicotinic acetylcholine receptor gene expression in rat

Neurally evoked muscle electrical activity suppresses nicotinic acetylcholine receptor (nAChR) gene expression in extrajunctional domains of adult muscle fibers. It has been proposed that this regulation is mediated by calcium influx through voltage-dependent L-type calcium channels but bypasses the sarcoplasmic reticulum in chick and mouse C2C12 cells. Here we report that in rat muscle calcium influx through L-type calcium channels preferentially reduced nAChR epsilon-subunit RNA via a post-transcriptional mechanism. In contrast, calcium release from the sarcoplasmic reticulum (SR) suppressed nAChR subunit RNA levels as a result of decreasing nAChR subunit promoter activity. Finally, we show that this decreased promoter activity is mediated through the same DNA sequences that control activity-dependent gene expression. Therefore, we propose that in rat muscle, calcium release from the SR participates in coupling muscle depolarization to nAChR gene expression.

Chronic antiprogestin therapy produces a stable atrophic endometrium with decreased fibroblast growth factor: a 1-year primate study on contraception and amenorrhea

OBJECTIVE

To describe the efficacy of mifepristone in the prevention of menstrual bleeding and ovulation, with similar observations in comparison groups.

DESIGN

Prospective experimental study. Thirty-two cynomolgus monkeys were divided equally into four treatment groups (n = 8). Treatment lasted for 1 year.

INTERVENTION(S)

Group I received GnRH-agonist (GnRH-a) and in-sequence mifepristone, group II received mifepristone only, group III received GnRH-a only, and group IV received vehicle control.

MAIN OUTCOME MEASURE(S)

Serum estradiol and progesterone, menstrual bleeding, endometrial thickness, and endometrial expression of basic fibroblast growth factor (bFGF) as determined by immunohistochemistry.

RESULT(S)

Weekly progesterone determinations showed that mifepristone-treated monkeys seldom ovulated (6 ovulations in 8 years), compared with the controls (100 ovulations in 8 years), while maintaining early to midfollicular levels of circulating serum estradiol. The GnRH-a-only group also rarely ovulated, but was chronically and severely hypoestrogenic. The mifepristone-only group showed scant menstrual bleeding (5 days in 8 years) as compared with the menstrual frequency in control animals (422 days in 8 years). Endometrial proliferation, as determined by biopsy, was similarly minimal for both the GnRH-a and mifepristone groups, and statistically less than in control monkeys. Both the mifepristone and GnRH-a treatments suppressed endometrial gland expression of the angiogenesis polypeptide bFGF.

CONCLUSION(S)

Chronic mifepristone induced anovulation along with virtual amenorrhea, which suggests the worth of this novel hormonal contraceptive.

A phase I and pharmacokinetic study of LY231514, the multitargeted antifolate

LY231514 is a novel antifolate that principally inhibits thymidylate synthase, but with additional folate-dependent enzyme targets. A Phase I study of single-agent LY231514 administered as a daily i.v. infusion over 10 minutes for 5 days, repeated every 3 weeks, was conducted to evaluate the maximum tolerated dose, pharmacokinetic profile, and antitumor activity of the drug using this schedule. Thirty-eight patients with advanced malignancies that were refractory or not amenable to standard therapy were treated with a total of 116 courses of LY231514, escalating treatment doses through 10 dose levels, from 0.2-5.2 mg/m2/day. No objective clinical responses were observed, although minor antitumor activity not fulfilling the response criteria was seen in three patients. A maximum tolerated dose of 4.0 mg/m2/day was determined, with neutropenia as the predominant dose-limiting toxicity. Reversible disturbances of liver biochemistry, fulfilling the protocol definitions of dose-limiting toxicity, were also observed. Other toxicities included diarrhea, mucositis, skin rash, and fatigue. Pharmacokinetic studies were performed at all treatment levels. Analysis showed a linear relation between administered dose and both maximum plasma concentration (Cmax) and area under the plasma concentration/time curve. The drug was cleared with a day 1 total body clearance of 108.9 +/- 38.8 ml/min/m2, with plasma concentrations declining with a mean harmonic terminal half-life of 1.4 +/- 0.98 h. When given by this schedule, LY231514 is tolerable, and Phase II studies are in progress.

REM measurements aboard MIR during 1995

Measurements of the South Atlantic Anomaly (SAA) made with the Radiation Environment Monitor (REM) aboard Mir from November 1994 to February 1996 are presented. During this period an increase of the SAA radiation by approximately 25% is observed, which coincides with a lowering of the radio solar flux. Radio solar flux is one of the parameters controlling the earth's atmospheric distribution and with it the absorption of inner radiation belt protons forming the SAA. Due to the altitude gradient of the atmospheric density, the proton fluxes in the SAA are anisotropic (loss cone, east-west effect). The measured distribution can be accounted for by basic models.

Cerebral areas associated with motor control of speech in humans

We have defined areas in the brain activated during speaking, utilizing positron emission tomography. Six normal subjects continuously repeated the phrase "Buy Bobby a poppy" (requiring minimal language processing) in four ways: A) spoken aloud, B) mouthed silently, C) without articulation, and D) thought silently. Statistical comparison of images from conditions A with C and B with D highlighted areas associated with articulation alone, because control of breathing for speech was controlled for; we found bilateral activations in sensorimotor cortex and cerebellum with right-sided activation in the thalamus/caudate nucleus. Contrasting images from conditions A with B and C with D highlighted areas associated with the control of breathing for speech, vocalization, and hearing, because articulation was controlled for; we found bilateral activations in sensorimotor and motor cortex, close to but distinct from the activations in the preceding contrast, together with activations in thalamus, cerebellum, and supplementary motor area. In neither subtraction was there activation in Broca's area. These results emphasize the bilaterality of the cerebral control of "speaking" without language processing.

Mapping of 228 ESTs and 26 genes into an integrated physical and genetic map of human chromosome 17

We have integrated genetic and physical mapping data for chromosome 17 subdivided into 26 bins, by using a panel of chromosome 17 deletion somatic cell hybrids. One hundred four short tandem repeat and STS markers have been localized into these bins and have enabled the ordering of 288 ESTs and 26 genes, including 142 ESTs that had not been previously sublocalized on chromosome 17. The mapping information of several genetic maps, as well as information obtained by radiation hybrid and STS content mapping of YACs, has been integrated using this hybrid panel. Although existing mapping information for chromosome 17 was generally consistent for many ESTs previously mapped, the map presented here further refines the location of ESTs, as well as demonstrating a number of discrepancies found in the 17q24-q25 region. We attribute these discrepancies to the fact that the current radiation hybrid panels were selected for retention of the thymidine kinase gene at 17q25, as well as to a low concentration of YAC contigs in this region. These data illustrate the benefit of combining multiple mapping techniques to obtain the greatest accuracy. The integration of maps developed by different methods will generate the most accurate genome maps, which may then be used for the generation of large insert clone contigs for chromosome sequencing. Additionally, accurate transcript maps generated by ESTs will greatly speed the isolation of genes linked to disease loci.

Comparison of the morphological transforming activities of dibenzo[a,l]pyrene and benzo[a]pyrene in C3H10T1/2CL8 cells and characterization of the dibenzo[a,l]pyrene-DNA adducts

C3H10T1/2CL8 (C3H10T1/2) mouse embryo fibroblasts were used to study the in vitro carcinogenic activities of dibenzo[a,l]pyrene (DB[a,l]P) and benzo[a]pyrene (B[a]P). The morphological transforming activities of these rodent carcinogens were compared using replicate concentration-response studies. In concentration ranges where both polycyclic aromatic hydrocarbons (PAHs) were active, DB[a,l]P proved to be four to 12 times as potent as B[a]P based on concentration. At lower concentrations DB[a,l]P was active at 0.10 and 0.20 microM, concentrations where B[a]P was inactive. This makes DB[a,l]P the most potent non-methylated PAH evaluated to date in C3H10T1/2 cells. DNA adducts of DB[a,l]P in C3H10T1/2 cells were analyzed by both TLC and TLC/HPLC 32P-postlabeling methods using mononucleotide 3'-phosphate adduct standards derived from the reactions of anti-DB[a,l]P-11,12-diol-13,14-epoxide (anti-DB[a,l]PDE) and syn-DB[a,l]P-11,12-diol-13,14-epoxide (syn-DB[a,l]PDE) with deoxyadenosine 3'-monophosphate and deoxyguanosine 3'-monophosphate. All of the DNA adducts observed in C3H10T1/2 cells treated with DB[a,l]P were identified as being derived from the metabolism of DB[a,l]P to its fjord region diol epoxides through DB[a,l]P-11,12-diol. The predominant adduct was identified as an anti-DB[a,l]PDE-deoxyadenosine adduct. Other major adducts were anti-DB[a,l]PDE-deoxyguanosine and syn-DB[a,l]PDE-deoxyadenosine adducts with minor amounts of syn-DB[a,l]PDE-deoxyguanosine adducts. These DNA adduct data are consistent with similar findings of DB[a,l]PDE-deoxyadenosine adducts in mouse skin studies and human mammary cells in culture.

Phase 1 trial of a candidate rotavirus vaccine (RV3) derived from a human neonate

OBJECTIVE

To conduct a phase 1 safety and tolerability trial of an oral rotavirus vaccine candidate RV3 in healthy volunteers.

METHODOLOGY

Double blind placebo controlled trial of a single 1 mL oral dose (6.5 x 10(5) fluorescing focus units [FFU]/mL) in 10 healthy young men, 10 3-4 year old children and 10 3 month old infants with a 4 week surveillance period. The study was undertaken at a children's hospital and nearby community in Melbourne, Australia.

RESULTS

All subjects successfully completed the trial. There were no significant side-effects attributable to the vaccine preparation in any age group. No shedding of vaccine virus was detected by enzyme immunoassay. There was evidence of an immune response in serum and/or gut secretions in two of five vaccinees in each age group.

CONCLUSION

RV3 rotavirus vaccine appears to be safe and well tolerated. Evidence of immunogenicity in some subjects after a single dose encourages further trials to determine immunogenicity after three doses, after reduction of viral dose, and without prior administration of buffer.

Localization of a growth suppressor activity in MCF7 breast cancer cells to chromosome 17q24-q25

Chromosome 17 is one of the most frequently altered chromosomes in malignant breast cancer. At least four genes implicated in breast cancer reside on chromosome 17 (p53, 17p13; Her-2/neu/ERBB2, 17q12; BRCA1, 17q21; and nm23, 17q22). In addition, allelic imbalance has been described for at least five regions of chromosome 17. We have previously shown that the introduction of a normal human chromosome 17 into the breast cancer cell line MCF7 by microcell mediated chromosome transfer (MMCT) results in the in vitro growth arrest of these cells within 8 weeks, suggesting the presence of a growth suppressor on chromosome 17. Additionally, we have shown that the tumor suppressor gene p53 is not responsible for this phenotype, as it is wild type in MCF7 cells, and overexpression has no effect on either the in vitro or in vivo growth of these cells. We have further localized this growth suppressor gene to 17q24-q25 by transfer of chromosome 17 hybrids containing defined deletions. Whereas transfer of hybrids that contained an intact 17q (delta43/A9 and delta26/A9) resulted in growth arrest, two hybrids with overlapping deletions at 17q24-q25, had no effect on growth of MCF7 cells. Molecular analyses revealed that 50/70 (71%) of the resulting delta2/MCF7 or delta624/MCF7 MMCT clones retained an intact introduced chromosome 17. In contrast, only 8/34 (24%) of delta43/MCF7 revertants (deleted for 17p13.1-pter) which escaped growth arrest showed no breakage of the introduced chromosome 17. We did not observe a preferential loss of an intragenic BRCA1 marker in the MMCT hybrids, excluding BRCA1 as the gene responsible for this growth arrest phenotype. These data therefore implicate a new growth suppressor gene involved in breast cancer that is localized to chromosome 17q24-q25.

Evaluation of the Heart and Stroke Foundation of Canada Research Scholarship Program: research productivity and impact

OBJECTIVE

To compare the research productivity, and its impact, of individuals awarded research scholarships from the Heart and Stroke Foundation of Canada (HSFC) with that of a parallel group of unsuccessful applicants during the funding years 1980/81 to 1989/90 inclusive. Research productivity was defined as the number of peer reviewed publications, and impact was evaluated from the number of publications cited; the number of citations per publication; the number of citations per individual; and the impact score.

STUDY SELECTION

Data were collected on 192 individuals. Cohorts were defined as successful and unsuccessful individuals entering the system in the same year. The study comprised 10 separate cohorts. Data were collected on yearly publications and citation counts for each individual. These data, along with journal impact factors, were obtained from the Institute for Scientific Information.

CONCLUSIONS

During the 10 years of the study, individuals funded by the HSFC published more papers, more of their papers were cited, and they received more citations per individual than the unfunded comparison group. This consistency in multiple indicators provides strong evidence that funded individuals are more productive and that their work has a greater impact on the body of knowledge in this area. Although this study cannot unequivocally show a direct causal relation between funding and research success, the trend as shown by the indicators studied suggests a beneficial effect.

Perioperative managed care reimbursements

Providing high quality health care is no longer enough to thrive in the world of managed care. You must first analyze your marketplace and then represent your service in negotiations with managed care companies. Contracting managers can provide valuable information when negotiating for your services or areas.

Metastatic carcinoid tumor imaged with CT and a radiolabeled somatostatin analog: a case report

Radiolabeled somatostatin analogs have shown uptake in a variety of tumors. These include carcinoid, Merkel cell carcinoma, pheochromocytoma, islet cell tumor, and other tumors with somatostatin receptors. Radiolabeled somatostatin analog imaging with Indium-111-DTPA-pentetreotide permits whole body imaging, providing a new safe and effective means for detection of primary tumors and metastatic foci in neoplasms with somatostatin receptors. This imaging modality is helpful in screening the entire body as well as evaluating questionable foci of disease identified by conventional imaging modalities. This case report demonstrates the utility of computed tomography (CT) and radiolabeled somatostatin imaging as complementary modalities in the workup of a patient with metastatic carcinoid tumor.

Comparison of the clinical abrasion resistance of six commercially available denture teeth

PURPOSE

Clinical abrasion of denture teeth has certain implications when dentures are worn in excess of the average useful lifetime. The purpose of this study was to evaluate clinical denture tooth wear over a period of 3 years.

MATERIAL AND METHODS

The wear of six commercially available denture teeth (Premierdent, Acrotone, vitapan, Rx1, Duravite, and Ivoclar Orthosit) and a seventh combination of teeth was compared. Seventy patients with complete dentures were divided into seven groups of 10 each to form the study population.

RESULTS

There were no significant differences among the commercial denture teeth. Porcelain/Vitapan teeth exhibited the highest amount of abrasion. Significant wear was also measured between the Ivoclar Orthosit and Porcelain/Vitapan teeth.

Observations of the low Earth orbit radiation environment from Mir

Recent measurements of the high-energy charged particle environment with the Radiation Environment Monitor (REM) aboard the Russian Mir space station are presented. Ionizing dose rates in a silicon detector have been measured with two shieldings. The dose is mainly accumulated in two distinct areas, the South Atlantic Anomaly (SAA) and the region of closest approach to the magnetic poles. Whereas the radiation in the South Atlantic Anomaly varied little during 1995, large changes of the daily absorbed doses in the polar regions are observed. A comparison of REM doses with the NASA AP-8 and AE-8 radiation models revealed major differences. AP-8 tends to underestimate the average REM doses, whereas AE-8 overestimates REM doses, and rather describes the worst case.

Human cerebral activity with increasing inspiratory force: a study using positron emission tomography

Human cerebral activity with increasing inspiratory force: a study using positron emission tomography. J. Appl. Physiol. 81(3): 1295-1305, 1996.--The major aim of this study was to use positron emission tomography (PET) to assess dose-dependent effects of inspiratory loads on relative regional cerebral blood flow as an indication of neuronal activation and recruitment. Six normal men underwent H2 15O-PET scanning during unloaded breathing and with external inspiratory loads (generating mouth pressures of -5, -10, and -15 cmH2O); positive-pressure ventilation against relaxed respiratory muscles acted as control. During unloaded breathing, the supplementary motor area was significantly activated. With the addition of the smallest load, activations also occurred in the right premotor area and bilaterally in the superolateral motor cortex (MI) in areas previously shown to be activated with deeper breathing. There was little further change in these areas with greater loads. Additional force-related activations occurred in the inferolateral sensorimotor cortex, parietal cortex, and midbrain/hypothalamus. The results suggest that volitionally induced increases in inspiratory muscle force are achieved via a complex integration of neuronal activations in cortical and subcortical regions associated with motor control.

Breathing during wakefulness and NREM sleep in humans without an upper airway

The increase in PCO2 that occurs during sleep may reflect an inadequate ventilatory compensation to an increase in upper airway resistance. To address this question in humans, we examined changes in breathing during wakefulness and non-rapid-eye-movement sleep in eight laryngectomized subjects who breathed through a tracheal stoma. In these subjects, any sleep-related increase in upper airway resistance could not affect ventilation. Healthy subjects breathing via an intact upper airway were studied as controls. The mean increase in end-tidal PCO2 from wakefulness to sleep was 2.7 +/- 2.6 (SD) Torr (P = 0.05) in laryngectomized subjects and 1.6 +/- 1.4 Torr (P = 0.02) in control subjects. During wakefulness, ventilation was lower in laryngectomized subjects compared with control subjects, although this difference was not statistically significant (6.8 +/- 1.9 vs. 7.4 +/- 1.2 l/min; P > 0.05). During sleep, the fall in ventilation was similar in the two groups (1.1 +/- 2.1 vs. 0.8 +/- 2.1 l/min; P > 0.05). Our observations are not consistent with the view that increases in upper airway resistance are obligatory for sleep-related CO2 retention in humans.

Biphasic modulation of cell growth by recombinant human galectin-1

Human soluble galactose-binding lectin (galectin-1) has been expressed as an Escherichia coli fusion protein, following the amplification by polymerase chain reaction of cDNA prepared from a human osteosarcoma cell line. The fusion protein is a functional beta-galactoside-binding lectin, as is the recombinant galectin when purified from the cleaved fusion protein. The recombinant galectin has a biphasic effect on cell proliferation. Unlike the fusion protein, it functions as a human cell growth inhibitor, confirming earlier findings with natural human galectin-1, though it is less effective than the natural galectin. This reaction is not significantly inhibited by lactose, and is thus largely independent of the beta-galactoside-binding site. At lower concentrations, recombinant galectin-1 is mitogenic, this activity being susceptible to inhibition by lactose, and thus attributable to the beta-galactoside-binding ability of the protein. Some tumour cells are susceptible to the growth-inhibitory effect, and the galectin-1 gene is expressed in both normal and tumour cells.

Does oxygen help dyspnea in patients with cancer?

Dyspnea in patients with advanced cancer is a common symptom that is difficult to treat. This study investigated whether oxygen helps to relieve rest dyspnea in patients with advanced cancer. In a single-blind controlled trial, oxygen and air were administered in random order to hospice patients reporting dyspnea at rest. Measurements of arterial oxygen saturation, lung function, and dyspnea (using a visual analogue scale [VAS] and Borg score) were made before and after each gas had been given for 15 min. Data from 38 patients were used: analysis of variance revealed that mean VAS levels during baseline conditions, breathing room air (59 mm), were significantly reduced after administration of either air (48 mm; p < 0.001) or oxygen (45 mm; p < 0.001); there was no significant difference for the mean VAS scores between oxygen and air administration. There was no statistically significant order of treatment effect. There was no difference in the response to oxygen or air in patients with a history of cardiopulmonary disease. The improvement in dyspnea with oxygen could not be predicted from a subject's initial level of hypoxia. Results suggested that benzodiazepines may potentiate the effect of oxygen. The overall conclusion is that oxygen and air can have a significant effect in reducing dyspnea at rest in patients with advanced cancer.

Pre-clamp cardioprotection by protein kinase C (PKC) inhibitor improves left ventricular function following canine normothermic arrest

Since protein kinase C (PKC) has been proven to be a mediator of neutrophil activation and of intracellular calcium homeostasis, its inhibition could protect the myocardium from the deleterious effects of ischemic/reperfusion inury (IRI). The principal objective of this study was to evaluate the efficacy of the PK inhibitor SPC-100270 (2S,3S)-2-amino, 3-octadecanediol in a canine model of IRI. A double-blind study was conducted in which 19 coonhound dogs received either SPC-100270 or a vehicle before going on cardiopulmonary bypass (CPB). After 60 minutes of global normothermic (37 degree C) cardiac arrest (cross-clamp time 65-81 minutes for SPC-100270 and 65-72 minutes for control) and discontinuation of CBP, an epicardial short axis view echocardiogram was performed and reviewed by a double-blinded observer to determine the ejection fraction (EF). EF value exceeded 20% in 5 out of 9 SPC-100270 animals (27%-44%) and in 0 of 10 controls (0%-16%). These data show that SPC-10027 significantly (p=0.01 by Fisher's Exact Test) increased the probability that the animals would exhibit an EF greater than 20%.

Ventilatory relief of the sensation of the urge to breathe in humans: are pulmonary receptors important?

1. The sensation of an urge to breathe (air hunger) associated with a fixed level of hypercapnia is reduced when ventilation increases. The aim of the present study was to investigate whether pulmonary receptors are important in this mechanism. 2. Five heart-lung transplant (HLT) subjects and five control subjects were studied during periods of mechanical and spontaneous ventilation. End-tidal Pco2 (PET,CO2) was increased by altering the level of inspired CO2. Throughout, subjects rated sensations of air hunger. Air hunger was also monitored during and immediately following maximal periods of breath-holding. 3. When the level of mechanical ventilation was fixed, both groups experienced a high degree of air hunger when PET,CO2 was increased by about 10 mmHg. At similar levels of hypercapnia, both groups derived relief from approximately twofold increases in tidal volume, although relief was slightly less effective in HLT subjects. This was reversible, with decreases in the level of mechanical ventilation rapidly giving rise to increased ratings of air hunger. 4. With breath-holding, all subjects obtained some respiratory relief within 2 s of the break point; there was no significant difference between the groups. 5. The results suggest that sensations of an urge to breathe induced by hypercapnia can be modulated by changes in tidal volume in the presumed absence of afferent information from the lung.

GIP regulates glucose transporters, hexokinases, and glucose-induced insulin secretion in RIN 1046-38 cells

Acute studies of glucose-dependent insulinotropic peptide (GIP) have shown that GIP can synergize with glucose in stimulating insulin secretion both in vivo and in vitro. Here we studied the effects of extended exposure of RIN 1046-38 cells, an insulin-secreting cell line, to GIP and the mechanisms by which GIP synergizes with glucose in stimulating insulin secretion. Incubation of the cells with 100 nM GIP in the presence of glucose for 12 h significantly increased insulin release (287 +/- 31.7 vs. 102 +/- 9.7 ng/mg protein; n = 3), intracellular insulin content (12.8 +/- 0.83 vs. 8.2 +/- 0.52 ng/mg protein; n = 3), and insulin mRNA (approximately 2.7-fold; 24 h incubation) when compared to cells cultured with glucose alone. The insulinotropic effects of GIP on RIN 1046-38 cells were accompanied by an up-regulation of GLUT-1 and hexokinase I mRNA (1.75-fold) compared to non-GIP-treated cells; mRNA levels of GLUT-2 and glucokinase were unchanged by GIP, in the presence or absence of glucose. Our study suggests that the mechanism by which extended exposure of RIN 1046-38 cells to GIP increases glucose-stimulated insulin secretion includes up-regulation of glucose sensing elements.

Hyperpnoea during and immediately after exercise in man: evidence of motor cortical involvement

1. The neurophysiological basis for the increase in breathing associated with exercise remains obscure. The present study uses positron emission tomography (PET) to measure relative regional cerebral blood flow (rCBF) in order to identify sites of increased neuronal activation during and immediately following exercise. 2. Male volunteers underwent H2(15)O PET scanning during two complementary studies. Firstly, six subjects performed right leg exercise, adequate to increase oxygen uptake 2.5-fold. Secondly, five different subjects were scanned immediately following bicycle exercise (adequate to increase oxygen uptake 5-fold) while breathing was still increased. In each study, as a control, scanning was also performed during matched passive isocapnic positive pressure ventilation; additionally, in the first study, passive right leg movement was performed. 3. Increases in relative rCBF were obtained in each individual and co-registered with their magnetic resonance image of the brain defining individual gyral morphology. 4. During exercise, individual and group analysis revealed significant relative rCBF increases in the left and right superomedial primary motor cortex (the motor cortical 'leg' areas) and also in the left and right superolateral primary motor cortex in areas previously shown to be associated with volitional breathing. After exercise, there was no significant increase in relative rCBF in the superomedial areas but such increases were still present bilaterally in the superolateral areas which had been activated during the exercise. Other relative rCBF increases were also found, both during and after exercise, in cortical and subcortical areas known to be involved in motor control. 5. The results from PET scans during and after exercise, taken together, provide evidence for motor cortical involvement in the exercise-related hyperpnoea in man.

Adaptation of nicotinic acetylcholine receptor, myogenin, and MRF4 gene expression to long-term muscle denervation

Muscle activity alters the expression of functionally distinct nicotinic acetylcholine receptors (nAChR) via regulation of subunit gene expression. Denervation increases the expression of all subunit genes and promotes the expression of embryonic-type (alpha 2 beta delta gamma) nAChRs, while electrical stimulation of denervated muscle prevents this induction. We have discovered that the denervation-induced increases in alpha, beta, gamma, and delta subunit gene expression do not persist in muscles that have been denervated for periods extending beyond a couple of months. However, expression of RNA encoding the epsilon-subunit remains elevated suggesting a return to expression of predominantly adult-type (alpha 2 beta delta epsilon) nAChR in long-term denervated muscles; a finding confirmed by single channel patch-clamp analysis. Since the nAChR subunit genes are regulated by the MyoD family of muscle regulatory factors, and the genes encoding these factors are also induced following short-term muscle denervation, we determined their level of expression in long-term denervated muscle. Although MyoD and myf-5 RNA levels remained elevated, myogenin and MRF4 RNAs were induced only transiently by muscle denervation. Surprisingly, Id-1, a negative regulator of transcription, was gradually induced in denervated muscle with RNA levels peaking about two months after denervation. It is likely that this maintained level of increased Id expression, in conjunction with the returning levels of myogenin and MRF4 expression, account for the reduced level of embryonic receptors in long-term denervated muscle. These changing patterns of gene expression may have important consequences for the ability of muscle to recover function after denervation.

Modulation by "central" PCO2 of the response to carotid body stimulation in man

We describe a method to assess the effects of PCO2, around and below eucapnia, on the neuromuscular ventilatory response to a standard peripheral chemoreceptor stimulus. Subjects were "passively" hyperventilated (without respiratory muscle activity), at a constant level of ventilation. Stimuli (3-7 breaths N2) were delivered over a range of steady-state PETCO2 (25-43 mmHg). Stimuli during hypocapnia were coupled with a transient increase in FICO2 so that the stimulus to the peripheral chemoreceptors was always "hypoxia at eucapnia". Responses to the stimuli (quantified from the reduction in peak inflation pressure and the magnitude of the evoked diaphragm electromyographic activity) decreased in a graded manner as steady-state PETCO2 fell, disappearing at 7.5 mmHg below eucapnia. Carotid body chemoreceptor recordings from two anaesthetised cats, indicated that the peak firing rate during such stimuli was independent of steady-state PETCO2. The results suggest that the central sensitivity to a peripheral chemoreceptor input may be modulated by changes in steady-state PCO2 around eucapnia and during mild hypocapnia.

Oral efficacy of a leukotriene B4 receptor antagonist in colitic cotton-top tamarins

Leukotriene B4 (LTB4) is a potent neutrophil activator and chemotaxin that is present in increased concentrations in the colonic tissue and rectal dialysates of acute ulcerative colitis patients. Cotton-top tamarins (CTTs) with confirmed active colitis were treated with the second generation LTB4 receptor antagonist, SC-53228 ((+)-(S)-7-[3-(2-cyclopropyl-methyl)-3-methoxy-4-[(methylamino) carbonyl]phenoxy]propoxy]-3,4-dihydro-8-propyl-2H-1-benzopyran-2- propanoic acid), 20 mg/kg bodyweight by gavage, twice daily for 56 days. End points were body weights, stool consistency, colonic endoscopy, assay of inflammatory mediators, and haematology and clinical chemistry tests. LTB4 and prostaglandin E (PGE) values were measured in rectal dialysates at pretreatment, 28 day and 56 day time points. LTB4 concentrations were reduced from pretreatment mean (SEM) values of 37.3 (0.8) ng/ml to 3.7 (0.8) ng/ml (p < 0.001) and 2.3 (0.5) ng/ml (p < 0.01) at days 28 and 56, respectively. On the other hand, mucosal protective PGE values remained constant or slightly increased during SC-53228 treatment (pre: 6.9 (2.2) ng/ml; day 28: 6.7 (1.4) ng/ml; day 56: 9.9 (1.6) ng/ml). Furthermore, assessment of a panel of 35 clinical chemistry and haematology parameters throughout the treatment showed there were no significant untoward effects of drug treatment. Six CCTs finished the eight week treatment and five of six gained weight (ranging from 27-121 grams each) while one CTT lost weight (50 g). Stool condition improved in five of six animals while one of six remained unchanged. All CCTs showed dramatic improvement histologically, with no or only minimally active colitis after treatment. The histological changes plus significant weight gains and improvement of stool condition (quality of life parameters) after eight weeks of SC-53228 treatment were remarkable. Furthermore, in follow up biopsies seven months after treatment ceased, three of six CTTs had no active colitis. This is the first time afflicted CTTs have not had recurring colitic exacerbations after a treatment regimen was stopped. It is concluded that in colitic CTTs, SC-53228 has shown both an immediate and a long acting anticolitic activity. It is also concluded that reduced LTB4 concentrations during treatment inhibited neutrophil infiltration of the colonic tissue and this, coupled with the maintenance of mucosal protective prostaglandins, contributed to the dramatic anticolitic efficacy. The treatment was safe over eight weeks. A compound such as SC-53228 may be useful in the medical treatment of human inflammatory bowel disease.

Evidence for limbic system activation during CO2-stimulated breathing in man

1. The role of supra-brainstem structures in the ventilatory response to inhaled CO2 is unknown. The present study uses positron emission tomography (PET), with infusion of H2(15)O, to measure changes in relative regional cerebral blood flow (rCBF) in order to identify sites of increased neuronal activation during CO2-stimulated breathing (CO2-SB) in awake man. 2. Five male volunteers were scanned during CO2-SB (mean +/- S.E.M.; end-tidal PCO2, 50.3 +/- 1.7 mmHg; respiratory frequency, 16.4 +/- 2.7 min-1; tidal volume, 1.8 +/- 0.2 l). As control, scans were performed during 'passive' isocapnic (elevated fraction of inspired CO2) positive pressure ventilation (end-tidal PCO2, 38.4 +/- 1.0 mmHg; respiratory frequency, 15.5 +/- 2.2 min-1; tidal volume, 1.6 +/- 0.2 l). With CO2-SB, all subjects reported dyspnoea. 3. The anatomical locations of the increases in relative rCBF (CO2-SB versus control) were obtained using magnetic resonance imaging. 4. Group analysis identified neuronal activation within the upper brainstem, midbrain and hypothalamus, thalamus, hippocampus and parahippocampus, fusiform gyrus, cingulate area, insula, frontal cortex, temporo-occipital cortex and parietal cortex. No neuronal activation was seen within the primary motor cortex (at sites previously shown to be associated with volitional breathing). 5. These results suggest neuronal activation within the limbic system; this activation may be important in the sensory and/or motor respiratory responses to hypercapnia in awake man.

How exercise can help people with mental health problems

The researcher describes the outcomes gained by a young man with a diagnosis of chronic schizophrenia who participated in a 12-week progressive exercise programme. Using the Brief Psychiatric Rating Scale and the Nurses Observational Scale for Inpatient Evaluation, the researcher was able to evaluate any changes in the patient. There were significant changes in his psychological functioning, communication, animation, personal interest, motivation and insight into his body image. His physical fitness levels also improved and he showed less motor retardation and less body tension.

Phase I clinical and pharmacokinetic study of 3'-deamino-3'-(2-methoxy-4-morpholinyl)doxorubicin (FCE 23762)

Methoxymorpholinyldoxorubicin (FCE 23762) is a novel, highly lipophilic doxorubicin analogue. It possesses potent in vitro and in vivo antitumor activity including efficacy in multidrug-resistant tumor cell lines. It is also metabolically activated in vivo resulting in an 80-fold increase in potency over the parent drug. In this phase I study the drug was administered by i.v. bolus injection at 3-week intervals. Fifty-three patients with refractory solid tumors were treated; 133 courses of FCE 23762 were administered at doses ranging from 30 to 2250 micrograms/m2. The dose limiting toxicity was reversible myelo-suppression (granulocytopenia and thrombocytopenia), demonstrating a delayed nadir and recovery in comparison to doxorubicin. Other toxicities included transient elevation of hepatic transaminases, delayed and prolonged nausea and vomiting, mucositis, anorexia, fatigue, and diarrhea. Heavily pretreated patients demonstrated more myelosuppression than previously untreated patients at 1250 micrograms/m2. No cardiotoxicity was observed. Four objective tumor responses were seen: one complete response in a patient with pelvic recurrence of cervical cancer; one partial response in a patient with cutaneous and lymph gland metastases from head and neck cancer; and two minor responses in patients with liver metastases from colorectal cancer. Plasma concentrations of FCE 23762 and its 13-dihydro metabolite, FCE 26176, were measured in 20 patients at doses > or = 675 micrograms/m2, using HPLC with fluorescence detection. The area under the plasma concentration-time curve ranged from 30 to 80 ng/h/ml; plasma data suggested linear kinetics in the range of tested doses (although there was considerable interpatient variability). The maximum tolerated dose defined in this study using this schedule is 1500 micrograms/m2. A safe phase II dose for previously untreated patients using this schedule is 1250 micrograms/m2; however, this may actually be below the optimal dose for this patient population.

Changes in total pulmonary resistance and PCO2 between wakefulness and sleep in normal human subjects

We investigated the possible role of an increase in total pulmonary resistance in the sleep-related hypoventilation that occurs in healthy subjects. Eight nonsnoring volunteers were studied during quiet wakefulness and stage IV sleep. Airflow was measured via a nasal mask with a low dead space, and breathing pattern, end-tidal PCO2 (PETCO2), and a continuous estimate of total pulmonary resistance were estimated. From wakefulness to sleep, mean inspiratory resistance increased from 5.5 +/- 2.4 (SD) to 8.1 +/- 4.3 cmH2O.l-1.s, PETCO2 increase from 38.7 +/- 3.0 to 40.7 +/- 3.5 Torr, and ventilation decreased from 7.12 +/- 1.15 to 6.47 +/- 1.68 l/min. In five of the eight subjects, low levels of continuous positive airway pressure were applied during stage IV sleep to reverse any increase in resistance. In these subjects, continuous positive airway pressure reduced mean inspiratory resistance from 9.3 +/- 4.3 +/- 3.0 cmH2O.l-1.s but had little effect on mean PETCO2 (from 39.8 +/- 4.0 to 39.6 +/- 4.0 Torr) and mean ventilation (from 6.79 +/- 1.93 to 6.91 +/- 1.80 l/min). These findings suggest that in nonsnoring subjects reductions in alveolar ventilation cannot be accounted for by an increase in airway resistance.

Is voluntary control of breathing impaired in patients with chronic obstructive pulmonary disease?

1. To assess whether voluntary control of breathing is impaired in patients with chronic obstructive pulmonary disease, a group of such patients performed a tracking task, requiring volitional control of respiratory muscles. 2. Eight patients (mean age 60 years; mean ratio of forced expiratory volume in 1 s to forced vital capacity = 31%) took part in the study. Five of the seven patients in whom blood gas measurements were made were mildly hypoxaemic (PaO2 = 53-71 mmHg), and one of these was hypercapnic (PaCO2 = 55 mmHg). Each subject performed a compensatory ventilatory tracking task using a tracking system which comprised a fixed target displayed on a monitor screen and a cursor moving in a line bisecting the target. The position of the cursor was perturbed by a forcing function and patients were required to keep the cursor on the target by breathing in and out of a spirometer. 3. To allow for any non-specific deficiency in motor control, patients performed a similar manual tracking task, using their dominant arm to move a joystick. As a control group, 11 healthy subjects (mean age 58 years; mean ratio of forced expiratory volume in 1 s to forced vital capacity = 77%) underwent an identical experimental protocol. 4. Motor control performances were measured in terms of the error between the target position and the subject's positioning of the cursor. Indices of performance were the root mean square of the error and the averages of the zero errors (i.e. end expiration/arm movement towards the trunk) and the peak errors (i.e. end inspiration/arm movement from the trunk).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of hyperglycemia duration on rabbit corneal thickness and endothelial ATPase activity

This study compares corneal thickness and corneal endothelial Na,K ATPase activity in normal and age-matched diabetic rabbits with up to 10 weeks of hyperglycemia. Corneal endothelial Na,K ATPase activity in normal rabbits increased between 10 and 20 weeks of age. Corneal thickness increased after 5 weeks of hyperglycemia. Decreased corneal endothelial homogenate Na,K ATPase activity was first seen after 10 weeks of hyperglycemia, though an earlier onset was possible due to sampling restrictions. Corneal endothelial homogenate Mg++ ATPase activity showed a transient increase after 2 to 5 weeks of hyperglycemia. This study shows that hyperglycemia in rabbit is associated with complex dynamic interactions between corneal thickness and corneal endothelial Mg++ ATPase and Na,K ATPase activities.

Somatotopy of human hand somatosensory cortex revealed by dipole source analysis of early somatosensory evoked potentials and 3D-NMR tomography

Somatosensory evoked potentials (SEPs) to median nerve and finger stimulation were analyzed by means of spatio-temporal dipole modelling combined with 3D-NMR tomography in 8 normal subjects. The early SEPs were modelled by 3 equivalent dipoles located in the region of the brain-stem (B) and in the region of the contralateral somatosensory cortex (T and R). Dipole B explained peaks P14 and N18 at the scalp. Dipole T was tangentially oriented and explained the N20-P20, dipole R was radially oriented and modelled the P22. The tangential dipole sources T were located within a distance of 6 mm on the average and all were less than 9 mm from the posterior bank of the central sulcus. In 6 subjects the tangential sources related to finger stimulation arranged along the central sulcus according to the known somatotopy. The radial sources did not show a consistent somatotopic alignment across subjects. We conclude that the combination of dipole source analysis and 3D-NMR tomography is a useful tool for functional localization within the human hand somatosensory cortex.