Biomedical subjects

A Baron

Publications and source records attributed to A Baron.

At least 91 records · Page 5Linked to original sources

PubMed1992

Gene expression of GLUT4 in skeletal muscle from insulin-resistant patients with obesity, IGT, GDM, and NIDDM.

In obesity, impaired glucose tolerance (IGT), non-insulin-dependent diabetes mellitus (NIDDM), and gestational diabetes mellitus (GDM), defects in glucose transport system activity, contribute to insulin resistance in target tissues. In adipocytes from obese and NIDDM patients, we found that pretranslational suppression of the insulin-responsive GLUT4 glucose transporter isoform is a major cause of cellular insulin resistance; however, whether this process is operative in skeletal muscle is not clear. To address this issue, we performed percutaneous biopsies of the vastus lateralis in lean and obese control subjects and in obese patients with IGT and NIDDM and open biopsies of the rectus abdominis at cesarian section in lean and obese gravidas and gravidas with GDM. GLUT4 was measured in total postnuclear membrane fractions from both muscles by immunoblot analyses. The maximally insulin-stimulated rate of in vivo glucose disposal, assessed with euglycemic glucose clamps, decreased 26% in obesity and 74% in NIDDM, reflecting diminished glucose uptake by muscle. However, in vastus lateralis, relative amounts of GLUT4 per milligram membrane protein were similar (NS) among lean (1.0 +/- 0.2) and obese (1.5 +/- 0.3) subjects and patients with IGT (1.4 +/- 0.2) and NIDDM (1.2 +/- 0.2). GLUT4 content was also unchanged when levels were normalized per wet weight, per total protein, and per DNA as an index of cell number. Levels of GLUT4 mRNA were similarly not affected by obesity, IGT, or NIDDM whether normalized per RNA or for the amount of an unrelated constitutive mRNA species. Because muscle fibers (types I and II) exhibit different capacities for insulin-mediated glucose uptake, we tested whether a change in fiber composition could cause insulin resistance without altering overall levels of GLUT4. However, we found that quantities of fiber-specific isoenzymes (phopholamban and types I and II Ca(2+)-ATPase) were similar in all subject groups. In rectus abdominis, GLUT4 content was similar in the lean, obese, and GDM gravidas whether normalized per milligram membrane protein (relative levels were 1.0 +/- 0.2, 1.3 +/- 0.1, and 1.0 +/- 0.2, respectively) or per wet weight, total protein, and DNA. We conclude that in human disease states characterized by insulin resistance, i.e., obesity, IGT, NIDDM, and GDM, GLUT4 gene expression is normal in vastus lateralis or rectus abdominis. To the extent that these muscles are representative of total muscle mass, insulin resistance in skeletal muscle may involve impaired GLUT4 function or translocation and not transporter depletion as observed in adipose tissue.

Adult↗

PubMed1992

Smokers with IDDM experience excess morbidity. The Colorado IDDM Registry.

OBJECTIVE--To determine whether there is an association between smoking and the self-reported morbidity of people with IDDM and to evaluate the nature of a possible interaction between smoking and IDDM in increasing the risk of morbidity among smokers with IDDM. RESEARCH DESIGN AND METHODS--Subjects were non-Hispanic whites aged 18-28 yr who participated in the Colorado IDDM Registry Follow-up Survey (case subjects, n = 24) or the 1985 NHIS (control subjects, n = 5876). Assessments of self-reported morbidity included any hospitalization in the past year; bed days, sick days, and limited-activity days in the past 2 wk; and ratings of poor health. The criteria outlined by Saracci were used to determine whether smoking was associated with greater morbidity among IDDM case compared to control subjects (smoking by IDDM interaction). RESULTS--Age- and sex-adjusted ORs, estimated from logistic regression, showed that people with IDDM reported excess morbidity compared with control subjects, regardless of smoking status. Smokers with IDDM reported morbidity 3-10 times as often as nonsmoking control subjects and were 2-3 times more likely to report morbidity than nonsmokers with IDDM. The smoking by IDDM interaction was more than multiplicative for all morbidity measures. Fifty to 75% of excess morbidity in young smokers with IDDM over simple additive effects was related to the interaction between smoking and IDDM. CONCLUSIONS--There was excess reported morbidity among people with IDDM who smoked, greater than that expected from the combined effects of smoking and IDDM. Smoking cessation in young people with IDDM may alleviate some of this excess, but more study is needed to determine whether smoking serves as an indicator of poor IDDM care practices or has a physiological impact that compounds the morbidity experienced by people with IDDM.

Adult↗

PubMed1991

Production and specificity of monoclonal antibodies against calmodulin from Dictyostelium discoideum.

Monoclonal antibodies were raised against calmodulin purified from Dictyostelium discoideum. To increase its antigenicity, the calmodulin was conjugated to keyhole limpet hemocyanin; mice were immunized with the conjugate. Hybridomas producing antibodies against calmodulin were identified by screening culture supernatants with calmodulin coupled to bovine serum albumin. The specificity of antibodies from hybridoma culture supernatants was tested by Western blot of Dictyostelium cell lysates. For the purpose, methods were developed that permitted sensitive detection of calmodulin bound to membranes. The key elements of the blotting protocol were used of PVDF membrane, transfer conducted in phosphate buffer, and glutaraldehyde fixation after transfer. These methods permitted detection of as little as 0.1 ng of calmodulin spotted directly onto the membrane, or 10 ng transferred from an SDS polyacrylamide gel. Ten calmodulin-specific antibodies were identified; most of these reacted preferentially with the calcium-containing form of Dictyostelium calmodulin. Several of the monoclonal antibodies cross-reacted with calmodulin from bovine brain.

Animals↗

PubMed1991

Pharmacological block of Ca(2+)-activated Cl- current in rat vascular smooth muscle cells in short-term primary culture.

Ca(2+)-activated Cl- currents were studied in isolated cells from rat portal vein smooth muscle in short-term primary culture using the whole-cell patch-clamp technique. Cl- currents can be activated separately by Ca2+ release from intracellular stores (in response to external applications of caffeine or noradrenaline) and by Ca2+ influx through voltage-dependent Ca2+ channels. The effects of several Cl- channel blockers and of spironolactone (a substance known to reduce internal Ca2+ loading) on both Cl- and Ca2+ currents were examined. Diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), anthracene-9-carboxylic acid (9-AC) and diphenylamine-2,2'-dicarboxylic acid (DPC) inhibited the Ca(2+)-activated Cl- current (IC50 values between 16.5 and 306 microM) with no effects on the inward Ca2+ current and on internal Ca2+ loading (testing by measuring the Ca(2+)-activated K+ current). These results indicate that the inhibition of Cl- current by these compounds is due to a direct interaction with the Cl- channel. In contrast, spironolactone inhibited both K+ and Cl- currents (IC50 = 7.6 microM) by reducing the amount of Ca2+ located in the internal stores, whereas the Cl- current activated by Ca2+ current through T-type Ca2+ channels was unchanged. This preparation and the protocols developed in this study appears to be appropriate for analysis of substances interfering with Cl- channels or intracellular Ca2+ stores.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1991

Ca2+ channel activation and membrane depolarization mediated by Cl- channels in response to noradrenaline in vascular myocytes.

1. The effects of noradrenaline (NA) were studied on vascular smooth muscle cells isolated from rat portal vein. 2. Two types of single-Ca2+ channel currents with conductances of 17 pS and 8 pS were obtained in cell-attached configuration. Bath application of NA increased the open probability of both channels during depolarizing pulses without a change of background membrane conductance. However, NA did not open Ca2+ channels when the membrane patch potential was held at -50 mV, which is about the resting potential in physiological conditions. 3. In the whole-cell configuration, studies of voltage-dependent Ca2+ channel currents showed that the peak conductance curve was not shifted to more negative potentials by NA. 4. Measurements of internal Ca(2+)-concentration ([Ca2+]i) with Indo-1 indicated that NA increased [Ca2+]i at a holding potential of -50 mV and evoked a Ca(2+)-activated Cl- current. These effects were blocked when heparin was included in the pipette solution. 5. A Cl- channel blocker without effect on Ca2+ channels (anthracene-9-carboxylic acid) inhibited the contractions of portal vein strips induced by NA in a manner similar to that produced by a Ca2+ channel inhibitor (isradipine). The NA-induced contraction was completely suppressed in the presence of ryanodine which depletes intracellular Ca2+ stores. 6. The present study suggests that activation of Cl- channels by Ca2+ release produces a membrane depolarization which is a prerequisite for enhanced opening of voltage-dependent Ca2+ channels in response to NA in venous smooth muscle.

Animals↗

PubMed1991

Large conductance calcium-activated non-selective cation channel in smooth muscle cells isolated from rat portal vein.

1. Membrane currents of isolated smooth muscle cells from rat portal vein were studied using the whole-cell patch-clamp technique. 2. In addition to the Ca(2+)-dependent Cl- current, single-channel activities were recorded in response to external applications of 10 mM-caffeine, in the absence of EGTA in the pipette solution. The conductance of this novel type of channel was around 200 pS for membrane potentials ranging from -100 to +60 mV. 3. The single-channel activities were also induced by external application of noradrenaline (10(-5)M) or acetylcholine (10(-5)M), by Ca2+ entry through voltage-dependent Ca2+ channels, and by intracellular application of ryanodine (10(-5)M). The caffeine-activated single-channel currents disappeared when 10 mM-EGTA was added to the pipette solution or after replacement of external Ca2+ with Ba2+. These results show that these channels are Ca2+ dependent. 4. Alterations of the Cl- equilibrium potential did not produce any change in the reversal potential of the caffeine-activated single-channel current indicating that it was not carried by Cl- ions. The value of the reversal potential was about +10 mV, irrespective of the CsCl-, KCl- or NaCl-containing solutions used to fill the pipette. This observation indicates that the channel was equally permeable to these monovalent cations. 5. Caffeine activated single-channel currents when cells were bathed in 90 mM-Ba2+ plus 1 mM-Ca(2+)- or 91 mM-Ca(2+)-containing solutions, showing that divalent cations permeate the channels. The permeability for Ca2+ over Na+ was high as the ratio PCa/PNa was estimated to be 21. 6. Single-channel activities induced by caffeine were not modified by Ca2+ channel blockers such as dihydropyridines and phenylalkylamines. 7. It is concluded that portal vein smooth muscle cells possess Ca(2+)-activated nonspecific channels which are highly permeable to Ca2+ ions.

Animals↗

PubMed1991

Reduction in the elevated blood pressure of Dahl salt-sensitive rats treated chronically with L-5-hydroxytryptophan.

Rats of the Dahl salt-sensitive (DS) and Dahl salt-resistant (DR) strains were placed on a 4% NaCl diet and blood pressures were monitored. Chronic subcutaneous infusion L-5-hydroxytryptophan (L-5-HTP, 12.6 mg/day) by osmotic minipumps significantly decreased the elevated systolic blood pressure of DS rats on a 4% NaCl diet. Blood pressures of DR rats were unaffected by treatment with L-5-HTP. Cardiac hypertrophy was associated with Dahl salt-induced hypertension. However, treatment with L-5-HTP failed to reduce the weight of the heart significantly. These results suggest that chronic administration of L-5-HTP was effective in reducing the elevated blood pressure in the DS model. The specific mechanisms by which L-5-HTP reduces the elevated blood pressure in DS rats is not clear and remains for further study.

5-Hydroxytryptophan↗

PubMed1991

Effect of chronic dietary treatment with L-tryptophan on the development of cold-induced hypertension in rats.

This study was designed to assess the effect of chronic dietary administration (2.5 and 5.0% by weight) of the neutral amino acid, L-tryptophan, on the development of hypertension during chronic exposure to cold. In addition, a warm-adapted and cold-treated control group receiving unsupplemented food were used. Chronic administration of the lower dose of L-tryptophan (850 mg/day) prevented the elevation of blood pressure attenuated cardiac hypertrophy, and had no effect on body weight during exposure to cold. The higher dose of L-tryptophan (1,690 mg/day) attenuated the rate of blood pressure increase, did not affect cardiac hypertrophy, attenuated the gain in body weight, and increased the urinary output of epinephrine. Thus, this dose may be associated with some toxicity. Both doses of tryptophan failed to prevent certain other responses characteristically occurring during exposure to cold: i.e. increased weight of the kidneys, adrenal glands and brown adipose tissue; increased food and water consumption; increased dipsogenic responsiveness to angiotensin II, and increased plasma aldosterone concentration. The results indicate that chronic dietary administration of L-tryptophan (850 mg/day) can prevent the development of cold-induced hypertension, as it can in all other models of hypertension tested thus far in rats.

Aldosterone↗

PubMed1991

Effect of chronic treatment with clonidine and spironolactone on cold-induced elevation of blood pressure.

The present study was designed to determine whether antihypertensive agents known to affect the renin-angiotensin-aldosterone (RAA) system might affect the elevation of blood pressure induced by chronic exposure to cold. Spironolactone, a mineralocorticoid receptor blocker, was added to the food and administered to rats chronically exposed to cold. In addition, clonidine, and alpha 2-adrenergic agonist and inhibitor of renin secretion, was administered to another group of cold-exposed rats by daily intraperitoneal injection. A warm-adapted and a cold-treated control group were also used. Chronic administration of spironolactone prevented the development of hypertension but failed to prevent other adaptive physiological changes characteristically occurring during exposure to cold and seen in the cold-treated control rats. Thus, increased weight of the heart, kidneys, adrenals and brown adipose tissue, increased dipsogenic responsiveness to angiotensin II, increased urinary outputs of norepinephrine and epinephrine, and increased food and water consumption were observed in all rats, treated and untreated, during exposure to cold. Similarly, daily injection of clonidine attenuated the elevation of blood pressure but also failed to prevent the other adaptive physiological changes characteristic of cold. These results are consistent with the hypothesis that the RAA system plays a role in the development of the cold-induced elevation of blood pressure.

Aldosterone↗

PubMed1991

Calcium-activated cation channel in rat portal vein myocytes.

A rapid transient rise in the free cytosolic Ca2+ concentration is one of the earliest events in smooth muscle cell activation and is involved in the opening of several classes of Ca2(+)-sensitive ion channels such as K+ channels and Cl- channels. In portal vein smooth muscle cells, in addition to the Ca(2+)-dependent Cl-current, single-channel activities were recorded in response to external application of 10 mM caffeine, in the absence of EGTA in the pipette solution. The conductance of this novel type of channel was around 200 pS for membrane potentials ranging between -100 to +60 mV. The single-channel activities were also induced by external application of noradrenaline (10(-5) M) or acetylcholine (10(-5) M), by Ca2+ entry through voltage-dependent Ca(2+)-channels, and by intracellular application of ryanodine (10(-5) M). The caffeine-activated single-channel currents disappeared when 10 mM EGTA were added to the pipette solution or after replacement of external Ca2+ with Ba2+. These results show that these channels are Ca(2+)-dependent. Alteration of the Cl- equilibrium potential did not produce any change in the reversal potential of the caffeine-activated single-channel current, indicating that it was not carried by Cl- ions. The value of the reversal potential was about + 10 mV, irrespective of the CsCl-, KCl- or NaCl-containing solutions used to fill the pipette. Caffeine activated single-channel currents when cells were bathed in 90 mM Ba2+ plus 1 mM Ca(2+)- or 91 mM Ca(2+)-containing solutions, showing that divalent cations permeate the channels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed1990

Ligand specificities of recombinant retinoic acid receptors RAR alpha and RAR beta.

Binding of retinoic acid (RA) to specific RA receptors alpha and beta (RAR alpha and RAR beta) was studied. Receptors were obtained in two ways: (1) full-length receptors were produced by transient expression of the respective human cDNAs in COS 1 cells; and (2) the ligand-binding domains of RAR alpha and RAR beta were produced in Escherichia coli. RA binding to the wild-type and truncated forms of the receptor was identical for both RAR alpha and RAR beta, indicating that the ligand-binding domains have retained the binding characteristics of the intact receptors. Furthermore, RA bound with the same affinity to both RAR alpha and RAR beta. Only retinoid analogues with an acidic end-group were able to actively bind to both receptors. On measuring the binding of various retinoids, we have found that the properties of the ligand-binding sites of RAR alpha and RAR beta were rather similar. Two retinoid analogues were capable of binding preferentially to either RAR alpha or RAR beta, suggesting that it may be possible to synthesize specific ligands for RAR alpha and RAR beta.

Animals↗

PubMed1990

The murine genes Hox-5.1 and Hox-4.1 belong to the same HOX complex on chromosome 2.

Two different loci of Antennapedia-related homeobox-containing genes have been shown to map to mouse chromosome 2: the HOX-5 complex and the Hox-4.1 gene. These independently derived loci are likely to be parts of a single gene complex, although their close linkage has not yet been demonstrated. Since cosmid walks to extend the HOX-5 cluster and to potentially link the two loci were unsuccessful, we have used large restriction fragments separated by pulsed-field gel electrophoresis to demonstrate the linkage between probes from the HOX-5 region and sequences near Hox-4.1. To further define the distance between the two linked loci, we screened a NotI jumping library with sequences near the Hox-5.1 gene to obtain a marker within the region predicted to contain Hox-4.1. The jumping endpoint lies within genomic clones from a lambda phage walk extending from the 5' end of Hox-4.1, and thus provides clear evidence of linkage between the two Hox loci. Our results demonstrate that Hox-4.1 lies approximately 35 kb downstream of the Hox-5.1 gene and that the two loci do indeed thus constitute parts of the same HOX complex.

Animals↗

PubMed1990

Age-related effects of reinforced practice on recognition memory: consistent versus varied stimulus-response relations.

Healthy older (64-74 years) and younger (19-26 years) men received extended exposure to tasks requiring visual recognition memory (memory scanning). The older men's speeds increased substantially when fast responding was differentially reinforced by time limits placed on the recognition response. Gains were matched by the younger men, however, so that age differences were not reduced. These improvements by the older men occurred under conditions of varied stimulus-response relations (as well as consistent relations), a procedure that has been regarded as especially taxing of the cognitive resources of older adults. Although the study did not provide evidence that age differences in recognition memory were reduced by reinforced practice, the equivalent practice effects and the transfer of these effects from visual to auditory stimuli indicated that the older men's learning abilities were the equal of those of the young adult controls.

Adult↗

PubMed1990

A prospective study of principal care among Colorado neurologists.

We initially surveyed the practice patterns of 24 private sector neurologists in Colorado between June and September, 1985, having chosen representative practices from each of 4 practice types (solo [6], nonsolo single discipline [11], nonsolo multispecialty [4], and nonsolo HMO [3]) and from both urban (14) and rural (10) practice locations. Among 2,373 consecutive new patient visits initially surveyed, we reexamined 2,359 (99%) charts 1 year later to investigate patterns of principal care. We defined principal care as 2 or more follow-up visits in the year following the initial office visit. One-fifth of initial visits received principal care, and the mean number of follow-up visits per year among those receiving principal care was 4 (range, 2 to 32 visits). The best indicators of principal care were Medicare coverage, a classic neurologic diagnosis (seizure, stroke), rural practice location, and solo neurology practice. The best indicators of consultative care were self-pay coverage, a diagnosis of musculoskeletal, psychiatric, or pain disorder, urban practice location, and HMO neurology practice. Age, sex, race, and type of referring physician were unimportant in determining subsequent principal care. Projections of future manpower needs must reflect both consultative as well as principal care services provided by neurologists, as well as the cost-effectiveness of such care.

Adult↗

PubMed1990

Recognition memory in older adults: adjustment to changing contingencies.

Four older and 4 younger men were given extended exposure to a continuous-recognition memory procedure. Experimental variables included the type of stimulus (alphanumeric strings, words, or sentences), the intervals separating repeated items, gains and losses for correct and incorrect recognitions, and the extent of practice with the memory task. Signal detection analyses indicated that the older men generally were less accurate (sensitivity), particularly when the stimuli were strings, but that age differences decreased with practice. Under conditions in which the payoff matrix was neutral, the older and younger men showed equivalent rates of hits and false alarms (bias). Alteration of the matrix to require more liberal or more conservative patterns of recognition responding led to corresponding changes for men of both ages. Adjustments by the older men, however, were not as close to the bias values called for by the new matrices.

Adolescent↗

PubMed1989

Response slowing of older adults: effects of time-limit contingencies on single- and dual-task performances.

Younger and older men (18-25 vs. 65-76 years of age) were given extended practice (44 hr) with a memory scanning procedure in which lists of visual and auditory items were presented singly (single-task condition) or together with a second visual or auditory list (dual-task condition). For both age groups, identification of test items was slower with the dual-task procedure, and experience with the tasks produced only small changes in response latencies. When time limits were placed on responding, latencies decreased substantially, and the difference between single and divided tasks was reduced. Although the older men were slower throughout the experiment, the time limit contingency reduced age differences in responses to both tasks. The task effect was larger for the older men, but this age difference also was reduced by the time limit procedures.

Adolescent↗

PubMed1989

Age differences in manual versus vocal reaction times: further evidence.

Old and young adults responded to the spatial location of a stimulus, either by moving a lever in the direction of the stimulus or by saying the word corresponding to the direction into a microphone. For subjects of both ages, vocal responses were slower than manual responses, and reaction times increased with increased alternatives (1, 2, or 4 directions). In addition, the slopes of the functions relating reaction times to alternatives were steeper for vocal responses, a finding that is contrary to the report of smaller age differences in reaction time for vocal responses. The slopes of the vocal functions were similar, however, a finding suggesting that age differences in central processing rates are less for vocal than manual responses.

Adolescent↗

PubMed1989

The mouse Hox-1.4 gene: primary structure, evidence for promoter activity and expression during development.

This study reports the structure of the mouse homeobox-containing gene Hox-1.4 of the HOX-1 cluster, as well as its expression pattern during embryonic and fetal development. The overall structure of this gene includes two major exons, the second of which encodes the homeo-domain. The putative Hox-1.4 protein displays similarities with products of homologous genes located at the same relative positions in other HOX clusters. A fragment extending 360 base pairs (bp) upstream of a transcriptional start site was shown to be able to promote transcription in transfected cells. This fragment is GC-rich and contains binding sites for the Sp1 transcription factor. In situ hybridization studies revealed the Hox-1.4 expression pattern during development. As already reported for several other murine Hox genes, Hox-1.4 is expressed in the fetal central nervous system (CNS), in structures derived from somitic mesodermal condensations (sclerotomes, prevertebrae) as well as in several mesodermal components of various organs and structures such as lungs, gut, stomach, intestine and meso- and metanephros. This expression pattern is in good agreement with recent proposals concerning the involvement of such genes in the establishment of the vertebrate body plan as well as the relationship between the positions of these genes within their clusters and the anteroposterior restriction of their expression domains.

Amino Acid Sequence↗