Renal responses to sodium restriction in patients with early diabetes mellitus

Increased GFR and decreased renal vascular resistance are common renal hemodynamic changes in persons with early, uncomplicated, insulin-dependent diabetes mellitus. It has been hypothesized that excess total-body sodium in patients with diabetes contributes to the renal vasodilation, possibly by suppressing vasoconstricting neurohormonal systems. This study was undertaken to examine whether sodium restriction could normalize these renal abnormalities. Subjects were 12 male patients with uncomplicated insulin-dependent diabetes mellitus (duration, < 5 yr). Results were compared with those of an age- and gender-matched control group. All subjects received either a high-sodium diet (200 mmol/day) or a sodium-restricted diet (20 mmol/day) for 7 days, according to a randomized crossover protocol. GFR and RPF were measured using inulin and para-aminohippurate clearance techniques, respectively. Subjects with diabetes were maintained euglycemic during the clearance measurements. GFR was significantly higher in the diabetic group than in the control group with sodium repletion (124 +/- 4 versus 107 +/- 8 mL/min/1.73 m2; P = 0.03), and renal vascular resistance was significantly reduced (94 +/- 6 versus 107 +/- 17 mm Hg/L/min; P = 0.05). In response to sodium restriction, the hematocrit increased significantly in both groups, as did PRA and aldosterone, although responses in the diabetic group were somewhat blunted, indicating persisting volume expansion. Despite this humoral activation, sodium restriction had little effect on renal hemodynamic function in control subjects. In the diabetic subjects, this maneuver appeared to exacerbate the underlying renal abnormalities, with the GFR increasing to 131 +/- 4 mL/min/1.73 m2 (P = 0.05) and the renal vascular resistance declining to 73 +/- 5 mm Hg/L/min (P = 0.001). These data indicate that, rather than correcting renal hyperperfusion, sodium restriction exacerbates these characteristic abnormalities, suggesting that mechanisms other than suppression of vasoconstrictor activity are operative in the underlying renal hemodynamic abnormalities of early, uncomplicated, insulin-dependent diabetes mellitus.

Quantitation of vascular endothelial growth factor mRNA levels in human breast tumors and metastatic lymph nodes

In situ hybridization analysis provides a means to qualitatively study the heterogeneity of primary tumors and metastases based on the types of genes transcribed. In this study, we have tested some parameters for quantitative analysis of in situ hybridizations with paraffin-embedded human breast tumors and measured mRNA levels for the angiogenic protein, vascular endothelial growth factor (VEGF). VEGF mRNAs were highly tumor specific, with the highest levels near necrotic regions within the tissues (0.1 to 2.7 dpm/mm2). Normal cells within the tissue sections did not have detectable levels of VEGF mRNA. For comparison, tumor levels of c-myc (4 to 46 dpm/mm2) and glyceraldehyde-3-phosphate dehydrogenase mRNAs (48 to 214 dpm/mm2) were measured. The mRNAs for both of these genes were more broadly expressed across the tissue sections. The hybridization pattern for VEGF mRNAs was consistent with hypoxia-induced VEGF mRNA steady-state levels and supports the hypothesis that oxidative stress regulates VEGF expression in breast tumors.

The electrophilic, mutagenic and tumorigenic activities of phenyl and 4-nitrophenyl vinyl ethers and their epoxide metabolites

The metabolism and mutagenicity of phenyl and 4-nitrophenyl vinyl ethers (PVE and NPVE) and their epoxide metabolites, phenoxyoxirane (PO) and 2'-(4-nitro-phenoxy)oxirane (NPO), were studied including reactions with DNA and tests for carcinogenicity. PVE and NPVE were epoxidized in dry acetone by dimethyldioxirane to give high yields (95%) of the pure epoxides. The epoxides are unstable in aqueous media and in 0.1 N phosphate buffer, pH 7.4, at 37 degrees C; they had half-lives of 2.7 min (PO) and 4.4 min (NPO). These times were reduced to 1.9 min (PO) and 2.5 min (NPO) in the presence of isotonic (154 mM) chloride ion. In neutral phosphate buffer these epoxides hydrolyze to form glycolaldehyde and the corresponding phenols; in the presence of chloride ion, chloroacetaldehyde and several unknown compounds are also formed. Glycolaldehyde was also found as a hydrolysis product of the presumed epoxides generated in the hepatic microsomal oxidation of PVE and NPVE. PO and NPO reacted with DNA to form adducts that depurinated in weak acid to form 7-(2'-oxoethyl)guanine and N(2),3-ethenoguanine. PO was weakly mutagenic in Salmonella typhimurium TA1535 while NPO was much more mutagenic under the same conditions. PO and NPO were found to have mutagenic half-lives that matched their chemical half-lives. PO and NPO were found to be tumorigenic in the skin of mice after single or five initiating doses followed by multiple doses of phorbol ester (TPA). NPO was a stronger tumor initiator than PO. NPO had appreciable activity as an initiator of hepatoma formation in infant male B6C3F1 mice. Thus PO and NPO are electrophilic, mutagenic and tumorigenic metabolites of their corresponding phenyl vinyl ethers.

Angiotensin converting enzyme gene polymorphism and renal hemodynamic function in early diabetes

An insertion/deletion (I/D) of the human angiotensin converting enzyme (ACE) gene is a major determinant of circulating ACE levels. Recent studies suggest that the ACE I/D polymorphism may influence the risk of developing nephropathy in patients with insulin dependent diabetes mellitus (IDDM), although the mechanism responsible for the effect is unknown. Since an early increase in glomerular filtration rate (GFR) may also be a risk factor for the development of diabetic nephropathy, we sought to determine if the ACE I/D polymorphism influenced renal hemodynamic function in patients with IDDM. Genomic DNA was obtained from 39 normotensive male and female patients with uncomplicated IDDM (mean duration 3.4 years; range 1 to 6 years), and from 20 non diabetic control subjects. The ACE I/D polymorphism was determined using the polymerase chain reaction. Subjects were divided into three groups based on their ACE genotype. Values for GFR, renal plasma flow (ERPF), filtration fraction, and renal vascular resistance were determined in both groups using classic inulin and paraaminohippurate clearance techniques. Blood glucose was maintained between 4 to 6 mmol/liter in the patients with IDDM using a modified euglycemic clamp technique. Mean values for GFR were significantly greater in patients homozygous for the I allele (143 +/- 7 ml/min/1.73 m2) compared to patients homozygous for the D allele (121 +/- 3 ml/min/1.73 m2, P < 0.01), while the mean GFR values for the heterozygous patients were intermediate. ERPF was also significantly greater in patients homozygous for the I allele (850 +/- 103 ml/min/1.73 m2) compared to patients homozygous for the D allele (672 +/- 31 ml/min/1.73 m2, P < 0.04), while there were no differences in the values for mean arterial pressure, glycosylated hemoglobin, or albumin excretion rates amongst the groups. There was no dominant effect of the ACE gene I/D polymorphism in the control group. These results suggest that: (1) the ACE gene I/D polymorphism influences glomerular filtration and renal plasma flow rates in patients with early uncomplicated IDDM; and (2) differences in renal hemodynamic function do not appear to explain the protection against the development of diabetic nephropathy offered by the I allele.

Asbestos plaques in a typical Veteran's hospital population

Previous authors have described several pleural abnormalities on chest radiology as being pathognomonic for asbestos exposure. We sought to determine the percentage of admissions and outpatients at a typical Veteran's Affairs hospital with these findings, and researched medical records to verify the frequency at which patients having positive radiographs were suspected either by clinical/occupational history or radiologically to have had prior significant exposure to asbestos. Radiographs of 1,212 consecutive patients were evaluated by a certified B reader, and the medical records as well as previous radiology reports of all positive patients were reviewed. Twenty-eight (2.3%t) of the radiographs had pleural abnormalities consistent with asbestos exposure, with the patients, all male, ranging in age from 50 to 98 years (mean 75.6). Radiology reports described pleural plaques in only 12 of the 21 (57%) cases with prior exams available; in only seven (33%) was an asbestos etiology considered by the interpreting radiologist. The plaques were misdiagnosed in four instances as being indicative of other, unrelated pathology. A history of known dust exposure was expressed by only five patients (18%). Eleven described working in occupations now known to have a high incidence of exposure, but neither patient nor examining physician expressed consideration of dust inhalation. In conclusion, we have found that a significant percentage of patients in certain subpopulations show radiographic evidence of asbestos exposure that may be a harbinger of related pathology. Unfortunately, because of a low index of suspicion, thorough environmental histories are often deferred, many radiographic changes are either not recognized or are misdiagnosed, and these patients are not followed with the stringent protocols they deserve.

Pharmacokinetics of intrathecally applied BDNF and effects on spinal motoneurons

Brain-derived neurotrophic factor (BDNF) is a potential drug for treatment of amyotrophic lateral sclerosis. Previous studies have demonstrated little or no penetration of the blood-brain barrier by BDNF, hence systemic application does not result in significant penetration into the spinal cord to produce direct action on motoneurons. Intrathecal (i.th) application of BDNF to sheep was investigated as a mean of topical administration. After continuous infusion a caudalcranial gradient of BDNF concentration in cerebrospinal fluid (CSF) and at the meninges was observed. BDNF did not penetrate spinal parenchyma but accumulated in spinal motoneurons probably due to axonal uptake in ventral roots and subsequent retrograde transport. Spinal motoneurons showed reduced levels of tropomyosin receptor kinase (trk) B and increased levels of c-fos at high BDNF doses in comparison to treatment with saline, even after treatment periods of several months. After bolus injection and cessation of continuous delivery multiphasic reduction of the BDNF concentration in CSF was detected. Our study demonstrates that i.th. application of BDNF is feasible, setting the stage for future clinical trials.

An automated film masking and illuminating system versus conventional radiographic viewing equipment: a comparison of observer performance

RATIONALE AND OBJECTIVES

We compared observer performance in the interpretation of radiographs using an automated film masking and illuminating system (AFIS) with performance using standard radiographic viewing equipment.

METHODS

Observer performance was compared in three ways. In the first method, a radiographic pattern of vertical bars of varying conspicuity was shown to 11 subjects with use of the two different viewing systems. Subjects were not allowed to use a brightlight or handle the film. We then performed a receiver operating characteristic (ROC) study to compare observer accuracy in detection of low-contrast targets. ROC methodology was also used in the third portion of our study to compare the accuracy of interpretation of cervical spine radiographs by six radiologists. In both the second and third portions of our study, film handling and use of a bright-light was permitted to simulate clinical circumstances.

RESULTS

As a group, observers performed significantly better using the AFIS in the first (P < .001) and second (P < .05) portions of our study. There was no significant difference in performance in interpretation of cervical spine radiographs between the two viewing systems.

CONCLUSION

The AFIS enhanced low-contrast perception, but further research is needed to determine its ideal clinical applications.

Long-term ethanol administration alters the degradation of acetaldehyde adducts by liver endothelial cells

Previous reports have shown that long-term ethanol administration alters receptor-mediated endocytosis (RME) of a variety of macromolecules by liver endothelial cells (LEC). Acetaldehyde is the major metabolic product of ethanol metabolism and has been shown to bind to proteins to form adducts. In this study, the level of protein modification by acetaldehyde necessary for the uptake and degradation of acetaldehyde-modified proteins by LEC was investigated. Bovine serum albumin (BSA) acetaldehyde adducts were prepared by incubation of albumin with acetaldehyde at 100 mmol/L for 1 hour at 37 degrees C, and 1 mmol/L or 0.2 mmol/L for 5 days at 37 degrees C. In situ liver perfusion in the presence of these adducts resulted in the degradation of 107 +/- 10.02 microg, 69.82 +/- 5 microg, and 2.5 +/- 0.42 microg of acetaldehyde-adducted albumin, respectively, during a 4-hour period. These values were decreased by 53%, 67%, and nearly 100%, respectively, in livers from ethanol-fed rats. Additionally, modification of protein with 1 mmol/L of acetaldehyde for different periods of time and/or pH altered the amount of 14C-acetaldehyde binding, but no significant changes in degradation were observed. Finally, an excess of formaldehyde-modified albumin totally inhibited the degradation of acetaldehyde adducts, suggesting that they use the same receptor. These data show that acetaldehyde-modified proteins may be taken up and degraded by the scavenger receptor on LEC. This uptake and degradation are dependent on the extent modification of the protein by acetaldehyde, and long-term ethanol consumption decreases the degradation of acetaldehyde-protein adducts.

Detection of 1,N6-ethenodeoxyadenosine and 3,N4-ethenodeoxycytidine by immunoaffinity/32P-postlabelling in liver and lung DNA of mice treated with ethyl carbamate (urethane) or its metabolites

The capacity of the chemical carcinogen ethyl carbamate (EC, urethane) and its metabolites vinyl carbamate (VC) and vinyl carbamate epoxide (VCO) to form ethenobases was studied in liver and lung DNA of 12-day-old and adult CD-1, B6C3F1, C3H/HeJ and C57BL/6J mice. Following single and multiple doses of EC, VC or VCO, the formation of 1,N6-ethenodeoxyadenosine (epsilon dA) and 3,N4-ethenodeoxycytidine (epsilon dC) was quantified by an immunoaffinity chromatography/32P-postlabelling technique. Both etheno adducts were detected in untreated control DNA samples from liver and lung in the range of 2-15 adducts/10(9) parent nucleotides. Following five repeated injections of 250 or 280 nmol/g body wt VC to adult mice, 51, 57 and 78 epsilon dA/10(9) dA and 28, 42 and 42 epsilon dC/10(9) dC (means of duplicate analyses) were detected in liver DNA of CD-1, C3H/HeJ and C57BL/6J mice respectively. In lung DNA of these VC-treated mice, the levels were 87, 49 and 58 (epsilon dA/10(9) dA) and 64, 39 and 43 (epsilon dC/10(9) dC) respectively. Under similar dose regimens, lower levels of etheno adducts were detected in B6C3F1 mice. Etheno-DNA adducts were also formed in liver and lung upon treatment with EC in adult mice, but at 3-fold lower levels as compared with VC. In 12-day-old C3H/HeJ and C57BL/6J mice, 2- to 3-fold higher etheno adduct levels were detected in liver DNA, when compared with adults, upon a single treatment with 250 nmol/g body wt VC, suggesting that young animals are more susceptible to adduct formation. Combined analysis of adduct formation in adult CD-1, C3H/HeJ and C57BL/6J mice at the higher dose showed a statistically significant increase in etheno adduct formation in the order EC > VC. The results demonstrate that EC and its activated intermediates bind to liver and lung DNA to form epsilon dA and epsilon dC, and the differences in DNA binding further support the hypothesis that metabolic activation of EC to VC is involved. Preliminary data also suggest that background levels of epsilon dA and epsilon dC in DNA are affected by the type of diet given to the animals.

Native and non-native structure in a protein-folding intermediate: spectroscopic studies of partially reduced IGF-I and an engineered alanine model

The structure of a metastable folding intermediate of human insulin-like growth factor I (IGF-I) and an engineered model are investigated by circular dichroism and two-dimensional 1H NMR spectroscopy. The intermediate, which contains two of three native disulfide bonds, was trapped by acid quenching and isolated by reverse-phase HPLC. The reduced cysteine residues were mapped to residues 47 and 52 (corresponding to A6-A11 in insulin). In the native state this disulfide bridge anchors an adjoining amphipathic alpha-helix (helix 2; residues 42 to 49) against the hydrophobic core. Comparison of CD and 1H-NMR spectra demonstrates that the acid-quenched intermediate is partially folded and contains elements of native secondary and tertiary structure. Spectra are similar to those of an equilibrium model in which the reduced cysteine residues are replaced by alanine. Complete 1H-NMR sequential assignment of the alanine model has been obtained and demonstrates that removal of the disulfide bond is associated with local unfolding of the adjoining alpha-helix. Native secondary structure (including helices 1 and 3) is otherwise retained and defines a folded subdomain. Long-range nuclear Overhauser effects (NOE) within this subdomain are similar to those of native IGF-I; no non-native NOE is observed. Our results support the hypothesis that folding of the insulin motif is directed by a subset of native structural elements and that these elements form at an early step in the pathway. Formation of helix 2, despite its prominence in the native state, is likely to represent a late step. Hydrophobic collapse of this segment appears to precede helix formation.

Activation of H-ras oncogenes in male B6C3F1 mouse liver tumors induced by vinthionine or 2-chloroethyl-methyl sulfide

Vinthionine (S-vinyl-DL-homocysteine) is hepatocarcinogenic in rats and mice. [Vinyl-14C]vinthionine binds covalently to rat liver DNA, RNA and protein in vivo, but not in vitro. This amino acid is directly mutagenic in Salmonella typhimurium TA100 and TA1535; the mechanism of its metabolic activation in vivo in bacteria and liver is under study. In the present study liver tumors were induced in 12-day-old male B6C3F1 mice by single i.p. injections of vinthionine or the alkylating agent 2-chloroethyl methyl sulfide (CEMS). At 10 months the gross tumors were examined for the presence of activated H-ras oncogenes. DNA was isolated from single tumors per mouse from 37 mice treated with vinthionine and from 31 mice treated with CEMS. These DNAs were screened for codon 61 mutations by restriction fragment length polymorphism of PCR-amplified H-ras gene fragments. Thirty seven of 37 vinthionine-induced hepatomas had H-ras mutations in this codon, which consisted of seven C-->A transversions in the first base, with 29 A-->T transversions and one A-->G transition in the second base. Twenty five of 31 CEMS-induced hepatomas had mutations in the same codon, which consisted of seven C-->A transversions in the first base, with eight A-->T transversions and 10 A-->G transitions in the second base. These mutation spectra are quite different to that noted by others in spontaneous hepatomas in untreated B6C3F1 mice. These data appear to result from the covalent binding of these carcinogens to the liver DNA.

Congenital cystic adenomatoid malformation in the fetus: natural history and predictors of outcome

Cystic adenomatoid malformation (CCAM) is a rare lesion that often is diagnosed by prenatal ultrasonography. Outcome varies from hydrops and fetal death to resolution before birth. The authors reviewed their 7-year experience with 17 fetuses diagnosed with CCAM by prenatal ultrasonography to determine the natural history of the lesion and to identify factors that might predict outcome. Of the 17 fetuses, five died during intrauterine life (3 terminations, 2 fetal deaths); four of them had hydrops. Twelve fetuses were carried to term. Only one had prenatal intervention: a thoracoamniotic shunt at 24 weeks. All 12 infants survived and underwent resection. Only four required neonatal support (1 extracorporeal membrane oxygenation, 2 ventilator, 1 oxygen). The initial CCAM:chest ratio, degree of mediastinal shift at time of diagnosis, location of CCAM, and age at time of diagnosis did not correlate with outcome. Sonographically predicted pathological type did not correlate with pathological diagnosis after surgery, or with outcome. The only accurate predictors of outcome were presence of hydrops (all died) and decrease in size of CCAM during gestation (all survived). The outcome for fetuses with CCAM may be better than previously recognized. Many of the lesions decrease in size, despite significant mediastinal shift and lung compression at the time of diagnosis. Fetal intervention should be considered only for fetuses with hydrops. Others should be monitored with serial ultrasonography. Parental counseling, especially regarding pregnancy termination, should reflect the positive outcome noted in most cases.

Potent antisense oligonucleotides to the human multidrug resistance-1 mRNA are rationally selected by mapping RNA-accessible sites with oligonucleotide libraries

Antisense oligonucleotides can vary significantly and unpredictably in their ability to inhibit protein synthesis. Libraries of chimeric oligonucleotides and RNase H were used to cleave and thereby locate sites on human multidrug resistance-1 RNA transcripts that are relatively accessible to oligonucleotide hybridization. In cell culture, antisense sequences designed to target these sites were significantly more active than oligonucleotides selected at random. This methodology should be generally useful for identification of potent antisense sequences. Correlation between oligonucleotide activity in the cell culture assay and in an in vitro RNase H assay supports the proposed role of the enzyme in the mechanism of antisense suppression in the cell.

Blood conservation in acute care and critical care

Blood conservation has evolved into an important issue in hospital-based medicine. Increased awareness of and worry about transfusion-associated diseases have prompted a focus on this important area. New technologies, including continuous intraarterial monitoring devices, microchemical technologies, new drug development (recombinant human erythropoietin and aprotinin) and intraoperative salvage techniques have made the concept of clinically important blood conservation possible. In this article, the authors review clinically important areas regarding blood conservation, which are subsequently detailed in this issue of AACN Clinical Issues. Emphasis is placed on the need for blood conservation in acute and critical care practice and the technologies available to achieve this goal.

Pneumothoraces secondary to blunt abdominal trauma: aids to plain film radiographic diagnosis and relationship to solid organ injury

The objective was to identify subtle clues to the diagnosis of small pneumothoraces (PTX) in victims of blunt abdominal trauma (BAT) and to determine the relationship of PTX to solid organ injury. We retrospectively reviewed 1374 abdominal CT scans performed after BAT and assessed each for the presence of PTX and solid organ injury. In patients positive for PTX, the interpretation of the initial portable chest radiograph (PCXR) was noted and the film subsequently reviewed for subtle signs of PTX, presence of subcutaneous emphysema (SQE), and rib fractures. The initial PCXR of 50 consecutive blunt trauma admissions without CT evidence of PTX were reviewed for comparison. Eighty-four patients displayed PTX on CT, of whom 52 had initial PCXR available for review. Eight of 52 (15%) radiographs were initially interpreted as positive for PTX, whereas in our retrospective analysis, an additional 8 were discovered (total 31%). Of these, 23 of 52 (44%) had rib fractures, and 13 of 52 (25%) had SQE. Sixty-four of 1290 patients (5%) without CT findings of PTX sustained solid organ injury, whereas 15 of 84 (18%) with PTX had solid organ injury (significant by chi square analysis, P < 0.001). Although a large number of trauma-related pneumothoraces seen on CT will not be seen on admission PCXR, the search for rib fractures and SQE will enhance the sensitivity of detection. This has prognostic value, as the presence of PTX is related to a significantly increased incidence of abdominal solid organ injury.

Systemic treatment of white-tailed deer with ivermectin-medicated bait to control free-living populations of lone star ticks (Acari:Ixodidae)

Whole-kernel corn was treated with 10 mg ivermectin per 0.45 kg corn and fed at rate of approximately .45 kg/deer per day to white-tailed deer confined in the treatment pasture, whereas deer in an adjacent control pasture received a similar ration of untreated corn. Treatments were dispensed from February through September of 1992 and 1993, and free-living populations of lone star ticks. Amblyomma americanum (L.), were monitored in both pastures using dry-ice traps to quantify nymphs and adults and flip-cloths to assay the relative abundance of larval masses. Control values that were calculated for all ticks collected in both pastures during 1993 showed 83.4% fewer adults, 92.4% fewer nymphs and 100.0% fewer larval masses in the treatment versus control pasture. Serum ivermectin concentrations in treated deer averaged 21.7 and 28.3 ppb during 1992 and 1993, respectively. These values compared favorably with the goal concentration of 30.0 ppb which was anticipated under ideal conditions. This study demonstrates that a freely consumed, systemically active acaricidal bait ingested by white-tailed deer under nearly wild conditions can significantly reduce the abundance of all stages of free-living long star ticks.

Chest wall hamartoma in an adult: an unusual chest wall tumor

An asymptomatic intrathoracic mass was demonstrated on imaging studies in an adult. Operative removal was accomplished and it proved to be an extrapulmonary hamartoma arising from the soft tissue of the chest wall. This represents a rare location of this benign tumor in an adult.

Intrastriatal and intraventricular infusion of brain-derived neurotrophic factor in the cynomologous monkey: distribution, retrograde transport and co-localization with substantia nigra dopamine-containing neurons

The distribution and retrograde transport of brain-derived neurotrophic factor was examined using magnetic resonance imaging guided stereotaxic intracerebroventricular and intrastriatal infusion in the cynomologous monkey. Two intracerebroventricular animals were infused with brain-derived neurotrophic factor at a dose of 3 micrograms/h for 21 and 28 days. A third intracerebroventricular animal received sequential infusions of 15, 30 and 60 micrograms/h brain-derived neurotrophic factor each for seven days using an Alzet 2002 minipump. For the multiple intrastriatal animals (n = 5) a dose of 3 micrograms/h was infused into each site. One intrastriatal monkey was infused with vehicle solution of 10 mM phosphate-buffered saline pH 7.4 for 14 days resulting in no brain-derived neurotrophic factor immunoreactivity. Following the lower dose intracerebroventricular infusion, brain-derived neurotrophic factor immunoreactivity was confined to the ventricular ependymal layer. In the sequential higher dose intracerebroventricular case, the cannula was located mainly within the lateral ventricle, although there was damage to the ependymal wall and adjacent caudate nucleus. Brain-derived neurotrophic factor immunoreactivity revealed spread of injectate within the ipsilateral and to a lesser extent the contralateral caudate nucleus, septum, orbital cortex and ventricular ependymal wall. In this case, retrogradely labelled brain-derived neurotrophic factor neurons were found within the parafascicular thalamus and substantia nigra, pars compacta, as well as within cortex, vertical limb of the diagonal band and nucleus basalis. Brain-derived neurotrophic factor intrastriatal infusion retrogradely labelled perikarya within sensory motor cortex, parafascicular thelamus and substantia nigra, pars compacta. Sections from these cases dual-immunoreacted for brain-derived neurotrophic factor and tyrosine hydroxylase, the synthesizing enzyme for dopamine, revealed a subpopulation of pars compacta dopaminergic neurons which contained retrogradely transported brain-derived neurotrophic factor. These findings indicate that a select subgroup of nigral dopamine neurons retrogradely transport brain-derived neurotrophic factor in the primate. Furthermore it remains to be determined whether select nigral cells are responsive to the trophic influences of brain-derived neurotrophic factor in the normal and neuropathologic condition.

Behavioral and glucocorticoid responses of adult domestic dogs (Canis familiaris) to companionship and social separation

Removal of 1 member of a long-standing pair of adult domestic dog (Canis familiaris) kennel mates from the home run for 4 hr had no effect on the behavior or plasma glucocorticoid levels of the remaining dog. When tested in a novel environment, dogs showed increased activity and elevated glucocorticoid levels at the end of the session, but these responses were as large when the dogs were with their kennel mates as when they were alone. However, activity and glucocorticoid levels were not elevated if the dogs were exposed to the novel environment in the presence of their human caretaker. Dogs more often were observed in proximity with, and soliciting social behavior from, the human than the kennel mate. These results highlight the importance of human companionship for the domestic dog and point to a difference in the nature of the social relationships of dogs with humans and with conspecifics.

Effect of hyperglycaemia on arterial pressure, plasma renin activity and renal function in early diabetes

1. In insulin-dependent diabetes mellitus, hyperglycaemia has a profound effect on renal and systemic haemodynamic function. The mechanism for this is unknown. 2. We conducted a study in 11 males with insulin-dependent diabetes mellitus, within 6 years of diagnosis. We examined the neurohumoral, haemodynamic and renal variables during euglycaemia (4.0-6.0 mmol/l) and after a 12 h period of hyperglycaemia (8.5-10.5 mmol/l). Subjects were examined in a sodium-replete state during supine rest and during simulated orthostatic stress induced by lower body negative pressure at -15 mmHg. 3. Variations in glycaemia markedly influenced plasma renin activity, which was increased at baseline during hyperglycaemia (3.82 +/- 0.66 pmol of angiotensin I h-1 ml-1 compared with 2.13 +/- 0.33 pmol of angiotensin I h-1 ml-1 during euglycaemia, P = 0.009), and rose further during simulated orthostatic stress. Mean arterial pressure was also elevated during hyperglycaemia (89 +/- 2 mmHg compared with 81 +/- 3 mmHg during euglycaemia, P = 0.03), both at rest and during orthostatic stress. 4. The renal haemodynamic effects of hyperglycaemia included maintenance of glomerular filtration rate in the face of significant declines in renal blood flow, and a probable increase in filtration fraction (0.21 +/- 0.01 compared with 0.18 +/- 0.01 during euglycaemia, P = 0.06). The responses of mean arterial pressure and renal blood flow to simulated orthostatic stress were not affected by hyperglycaemia, but the forearm vascular response was significantly augmented. 5. These data suggest that sustained hyperglycaemia activates the renin-angiotensin system, thereby increasing systemic and renal vasomotor tone. Over time such changes may have deleterious microvascular consequences.

The enhancement of muscimol-stimulated 36C1 influx by the antispastic 5-aryl-3-(alkylsulfonyl)-4H-1,2,4-triazole (MDL 27,531) in rat brain membrane vesicles

The antispastic triazole, 4-methyl-3-methylsulphonyl-5-phenyl-4H-1,2,4-triazole (MDL 27,531) was tested in glycine- and muscimol-stimulated 36Cl- influx into brain membrane preparations. MDL 27,531 (100 nM) had no effect on glycine- (100 nM-400 microM) stimulated 36Cl- influx in brain stem tissue; on the other hand, MDL 27,531 (10 nM-10 microM) enhanced muscimol- (1 microM) stimulated 36Cl- influx in cerebellar but not cortical membranes. In the presence of the benzodiazepine (BZD) antagonist, flumazenil (10 microM), MDL 27,531 inhibited muscimol-stimulated flux. These data suggest a novel interaction of this triazole with subtypes of the gamma-aminobutyric acid (GABA)A receptor complex and the BZD receptor.