An investigation of intrinsic buffering power in rat vascular smooth muscle cells

Intrinsic buffering power (beta i) has been measured in vascular strips and single cells from rat mesenteric artery. Intracellular pH (pHi) regulation was inhibited to prevent overestimation of beta i due to acid extrusion or entry via regulatory processes. At resting values of pHi (7.0-7.2), a mean value of 41 +/- 4 mM/pH unit for beta i was found. beta i increased approximately fivefold from 30 to 150 mM/pH unit over the pHi range 7.5-6.5. The mean data relating beta i to pHi could be described by relating beta i to buffer concentrations and pKa. This gave a value of 310 mM for buffer concentration and a pKa of 6.0. As changes in pHi are known to have marked effects on vascular tone then the increase in beta i as pHi falls may be considered as a means of attenuating pHi decreases, before pH regulation restores pHi to resting levels.

Team business systems methods and strategies

Team management provides opportunities for both employers and employees. The advantages for the dentist employer are that responsibility is shared. As the team members grow in their understanding of the business, the burdens of management become lighter. Also, the perspectives of top team employees enrich the practice. Conversely, employees enjoy being part of the decision-making process. It is an opportunity for them to use their ideas and creativity in ways that benefit the development of the entire team.

Contribution of extracellular calcium to intracellular pH-induced changes in spontaneous force of rat portal vein

Normal spontaneous mechanical activity of isolated rat portal vein is critically dependent on external calcium as a source of contractile activation and this force is modified by alteration of intracellular pH. We have studied the involvement of the extracellular calcium pool in intracellular pH-induced changes in force. Intracellular pH was changed, at constant external pH, by NH4Cl application and withdrawal in bathing [CaCl2] varying between 3 and 0 mM, and manoeuvres were performed in the presence and absence of either the intracellular calcium mobilizer caffeine or the calcium channel blocker nifedipine. The results indicate that alteration of spontaneous force with intracellular pH has an absolute requirement for calcium entry from outside and calcium release from caffeine-sensitive intracellular stores.

Differential effects of external pH alteration on intracellular pH in rat coronary and cardiac myocytes

Changes in extracellular pH (pHo) induce changes in the intracellular pH (pHi) of cardiac myocytes that are slow and attenuated. Little however is known about the effects of changing pHo on the pHi of the coronary smooth muscle cells. We have therefore directly compared the effects of altering pHo on pHi of both coronary and cardiac myocytes. Carboxy-SNARF was used in single cells to measure pHi. Alteration of pHo caused corresponding changes in pHi that were large (70-80% of pHo) and rapid in coronary myocytes compared to cardiac myocytes. In contrast, changes of pHi produced by weak acids or bases produced similar pHi responses in both types of cells. It is suggested that the differential effects of pHo on coronary and cardiac cells may be functionally significant, as it will allow rapid alteration of coronary perfusion to meet tissue needs, while maintaining cardiac output.

Distribution and developmental pattern of neuromedin U expression in the rat gastrointestinal tract

This study has quantified, for the first time, the relative levels of neuromedin U (NmU) mRNA in the rat gastrointestinal tract using Northern blot analysis. NmU message was detected in all regions of the gastrointestinal tract from the oesophagus to the rectum. The greatest levels were found in the duodenum and jejunum, the principal sites for absorption, which were 2.5- and 3-fold respectively above ileal levels. Quantification of NmU mRNA and peptide contents in the duodenum, jejunum and ileum during postnatal development of the rat showed message and peptide levels to be greater in the maturing rat than in neonates. Message levels in the duodenum, jejunum and ileum showed 14-, 7- and 4-fold increases respectively between 1 and 56 days after birth, whilst the corresponding peptide levels in the duodenum, jejunum and ileum showed 33-, 14- and 25-fold increases respectively. Food deprivation caused a small, but significant, decrease in message levels in the jejunum and colon, but there was no change in the duodenum or ileum. This shows that the presence of food has little effect on NmU mRNA levels in the gut.

A quantitative study of the relation between intracellular pH and force in rat mesenteric vascular smooth muscle

Strips of rat mesenteric artery were loaded with carboxy-seminaphthorhodafluor (SNARF) to measure intracellular pH (pHi) and force simultaneously. pHi was altered by using weak acids and bases. Alkalinization produced an increase in force. For equal elevations of pHi a greater and faster increase of force was obtained in depolarized (high K+) than in non-depolarised preparations. Acidification produced little change in force unless the tissue was contracted (high-K+), in which case it elicited relaxation. Examination of the relationship between pHi and force in depolarized preparations showed that acidification produced a greater change in force than alkalinization. Removal of weak bases produced a transient acidification that was accompanied by a fall in force in all preparations. This was followed by a secondary contraction in depolarized preparations during the period over which pHi was acidic and being restored to resting values. Some preparations demonstrated a hysteresis in the relation between pHi and force. It is concluded that the relationship between pHi and force in mesenteric vascular smooth muscle is not constant but depends on the previous history of the preparation, and may involve differences in the interactions between H+, Ca2+ and the contractile machinery.

The in-vitro effects of insulin and the effects of acute fasting on cardiac beta-adrenoceptor responses in the short-term streptozotocin-diabetic rat

This study demonstrates that in-vitro incubation with insulin results in a reduction of the sensitivity of cardiac tissues from streptozotocin-diabetic rats to isoprenaline. Following incubation with insulin, the sensitivity of left atria and papillary muscles from diabetic animals was not significantly different from those of control animals. Insulin incubation had no effect on the sensitivity of diabetic tissues to forskolin or on ventricular beta-adrenoceptor number. Reduction of blood glucose in the absence of insulin by fasting, did not affect the sensitivity of tissues from diabetic animals to isoprenaline. These results suggest that insulin itself can directly reduce beta-adrenoceptor sensitivity without altering receptor number.

A comparison of the effects of intracellular and extracellular pH on contraction in isolated rat portal vein

1. The effects of changes in extracellular and intracellular pH on spontaneous contractile activity in isolated rat portal vein have been investigated. 2. Small strips of portal vein were loaded with the pH-sensitive fluorophore carboxy-SNARF and intracellular pH (pHi) and contraction were measured simultaneously at 37 degrees C. The tissue was superfused with oxygenated, Hepes-buffered solutions at pH 7.4. Intracellular pH was altered by isosmotic substitution of weak acids or bases. External pH (pHo) was altered by addition of strong acid or base to the solution. 3. The mean resting value of pHi was 7.06 +/- 0.03 (n = 28). Alteration of pHi led to changes in spontaneous activity. Addition of butyrate (20 mM) reduced pHi by 0.18 +/- 0.01 pH units (n = 8). Decreasing pHi produced an early, brief increase in contractile activity followed by a longer lasting decrease or even abolition of contraction. 4. Addition of 20 mM trimethylamine or NH4Cl increased pHi by around 0.2 pH units and produced an early transient decrease in contractile activity followed by a later maintained increase, both in frequency and magnitude. Removal of base produced a rapid rebound decrease in pHi which was associated with a further transient increase in contractile activity followed by decreased activity. The effects of base on both pHi and contraction were concentration dependent over the range investigated (2.5-30 mM). 5. Alteration of pHo produced a change in pHi in the portal vein. The pHi change was rapid compared to other non-vascular cells (about 1 min to half-maximal response).(ABSTRACT TRUNCATED AT 250 WORDS)

Changes of intracellular pH in rat mesenteric vascular smooth muscle with high-K+ depolarization

1. In mesenteric vascular smooth muscle cells changes in extracellular pH are rapidly transmitted to the cytoplasm. The mechanism involved is unknown, but it may be due to a high proton permeability of the surface membrane, in which case changes in membrane potential would alter the driving force for proton entry. We have therefore examined the voltage sensitivity of intracellular pH (pHi) in these cells. 2. Strips of mesenteric resistance vessels were loaded with SNARF-1 to monitor pHi and tension was simultaneously measured. Tissues were superfused with oxygenated solutions at 37 degrees C and pH 7.4. Isosmotic substitution of K+ for Na+ was used to depolarize the preparations. 3. pHi was found to be sensitive to alteration of [K+]. Depolarization of the tissue with K+ caused contraction and produced transient increases in pHi. When pHi regulation was blocked there was no significant change in the size of the alkalinization induced by high K+, thus it is unlikely that the results can be explained by voltage sensitivity of pHi regulating mechanisms. 4. In nominally Ca(2+)-free solution, the tissue does not contract and the alkalinization with high K+ was significantly greater than that occurring in 3 mM Ca2+. 5. There was a rapid acidification, when pHi regulation was blocked, which is consistent with a high proton permeability. 6. The effects of membrane potential on pHi have been modelled and show that they can be accounted for by effects of voltage on H+ influx through a proton channel. The effects of changing external pH on H+ influx also fit the model. Estimation of the proton permeability gave a high value (0.4 cm s-1). 7. The results presented demonstrate (i) a voltage sensitivity of pHi in mesenteric vascular smooth muscle cells and (ii) a particularly high permeability of the membrane to protons. The physiological significance of these findings is discussed.

Substrate-induced activation of dienelactone hydrolase: an enzyme with a naturally occurring Cys-His-Asp triad

The Cys-His-Asp catalytic triad found in dienelactone hydrolase (DLH) is unusual for several reasons. It has not been observed in other hydrolytic enzymes and it is virtually inactive when it is produced by site-directed mutagenesis in the proteases. We propose a model to explain why this triad is catalytically active in DLH but not in the proteases. In the resting state of DLH, His202 forms an ion pair with Asp171 and Cys123 exists as a thiol. The resting state thiol does not interact with His202 in the active site but instead forms a hydrogen bond with Glu36 in the interior of the molecule. In the absence of substrate, Glu36 is also ion paired with Arg206. When substrate binds, Arg206 forms a second ion pair with the anionic substrate and the Arg206/Glu36 ion pair weakens. The destabilized Glu36 carboxylate shifts towards and deprotonates the Cys123 thiol, thereby activating the nucleophile. As the thiolate anion is not energetically favoured in the hydrophobic interior of the enzyme, it swings into the active site where it can be stabilized by the His202 imidazolium and the dipole of helix C. The Cys123 thiolate which now lies adjacent to the acyl carbon of the substrate, is thus generated only in the presence of substrate. The mode of thiolate activation reduces the susceptibility of DLH towards thiol alkylating agents.

Extracellular pH signals affect rat vascular tone by rapid transduction into intracellular pH changes

1. Changes in extracellular pH (pHo) are known to produce large effects on vascular tone, but the mechanisms involved are not understood. As changes in intracellular pH (pHi) can also affect vascular tone, we have investigated the effects of changing pHo upon both pHi and tone. 2. Strips of rat mesenteric resistance vessels were loaded with the pH-sensitive fluorophore SNARF 1; thus tension and pHi could be simultaneously measured as pHo was altered. 3. Whenever pHo was altered there was a corresponding alteration of pHi. Furthermore, when pHo was changed the pHi change was more rapid than that reported to occur in other cells. The time to half-peak intracellular response was 38 +/- 4 s (n = 11). The induced pHi change was also less attenuated than in many other cells studied. Thus a ratio of 0.73 was obtained for the change in pHi per unit pHo change (n = 7). 4. An increase in pHi produced by an increase in pHo was accompanied by an increase in tension in the vascular strips. In other experiments pHi was increased at constant pHo by the addition of the weak base trimethylamine (40 mM). This also elevated tension in the strips. Conversely when pHo was changed while pHi was held at resting values, no change in vascular tone occurred. 5. It is concluded that the effects of pHo on vascular tone are due to the induced change in intracellular pH, and that the vascular smooth muscle cell is functionally well adapted to respond to changes in tissue pH, thereby allowing blood flow to a tissue to be rapidly altered to meet changing needs.

Nicotinic neuronal acetylcholine receptor alpha-3 subunit transcription in normal and myasthenic thymus

Thymic transcription of the alpha-3 subunit of the AChR was studied through sequencing and PCR analysis of thymic cDNA clones, Northern blotting, and ribonuclease protection assays. This analysis revealed at least three, 3' end sequence variants for the alpha-3 subunit as well as a variant that results from the alternative splicing of an antisense 122 bp Alu sequence between exons 5 and 6 of the normal transcript. The spliced Alu sequence not only shifts the exon 6 reading frame but also carries an in-frame stop codon. If translated, this variant transcript would produce a truncated peptide lacking the fourth transmembrane domain of the subunit and carrying a carboxy terminus dodecapeptide not found in any other known AChR subunit sequence. The putative variant subunit may lack biological activity and should differ antigenically from its normal counterpart. In comparing the normal, the MG hypertrophic, and the MG thymoma for transcription of the alpha-3 subunit and its 122 bp variant, it was found that there were no qualitative or quantitative changes in alpha-3 transcript expression in the MG hypertrophic thymi. Thymomas, however, showed an overall decrease in alpha-3 transcription and a comparative increase in beta-amyloid precursor transcription. The decrease in the levels of alpha-3 transcription in thymomas may be related to the proliferation of thymic epithelial cells.

Caterpillar bodies: distinctive, basement membrane-containing structures in blisters of porphyria

In a previous study, we reported on the observation of a relatively specific, linear body in the roofs of bullae from cases of porphyria cutanea tarda. In the present study, we expand on these observations to show the presence of these bodies in lesions of pseudoporphyria cutanea tarda and erythropoietic protoporphyria. Furthermore, we have applied immunoperoxidase techniques using antibodies to type IV collagen and laminin to show that they are composed of basement membrane material. Because the segmented, elongated shapes of these bodies reminded us of the larvae of butterflies, we coined the term "caterpillar bodies" to describe them. These bodies are similar in their composition to the Kamino bodies of Spitz's nevi, cylindrical bodies in adenoid cystic carcinoma, Civatte bodies of lichen planus, and the collagenous spherules seen in a number of conditions, and may provide a unique clue to the diagnosis of the porphyric bullous eruptions.

Characterization of rat gastric inhibitory peptide cDNA

Gastric inhibitory peptide (GIP) is a 42 amino acid gastrointestinal peptide which inhibits gastric acid secretion and stimulates pancreatic insulin secretion in the presence of glucose. Here we report the sequence of the cDNA encoding the rat GIP precursor. PreproGIP was 144 amino acids in length and comprised the GIP peptide itself, N- and C-terminal flanking peptides of 22 and 59 amino acids respectively and a typical hydrophobic signal peptide. The sequence indicated that GIP is released from its precursor by cleavage at single arginine residues. The C-terminal flanking peptide may have an important function since it was well conserved and contained a region of 16 amino acids with only a single, conservative replacement. Rat GIP mRNA was found in the duodenum and jejunum. Levels of GIP mRNA in the duodenum were increased twofold after a period of 2 days of starvation. There was no detectable expression of the GIP gene in other parts of the gastrointestinal tract or in other endocrine tissues. However, in pancreatic mRNA preparations, a larger mRNA was detected after low stringency hybridization. This could represent a further member of this gene family.

Characterization of complementary DNA encoding the rat neuromedin U precursor

Neuromedin U (NmU), a peptide originally isolated from porcine spinal cord, is known for its ability to stimulate uterine smooth muscle contraction and to cause selective vasoconstriction. It was subsequently isolated from a number of species. Among the species studied, the five amino acids at the C-terminus of the peptide are totally conserved, suggesting that this region is of major importance. We have cloned and sequenced the cDNA encoding the rat NmU precursor protein using the anchor polymerase chain reaction technique. Sequence analysis revealed that NmU is synthesized as a 174-amino acid precursor. Like the precursors of most other small regulatory peptides, it has a hydrophobic signal peptide and a number of paired dibasic amino acids, which may serve as signals for enzymatic cleavage, to release NmU and a series of other peptides. These predicted flanking peptides of NmU show no significant homology with entries in the protein databases searched, and the cDNA likewise shows no homology with entries in the GenBank database. Northern blot analysis using total RNA extracted from different rat tissues shows high levels of NmU mRNA in the ileum, thyroid, and anterior pituitary. Southern blot analysis of rat genomic DNA demonstrates that NmU is a single copy gene.

Outflow resistance and early occlusion of infrainguinal bypass grafts

Distal outflow vascular resistance (VR) has been measured intra-operatively during 67 infrainguinal bypass procedures to establish whether it might have a role as a predictive test for early graft thrombosis. The graft outflow was popliteal artery above the knee (48), popliteal artery distal to the knee (6) or a single calf vessel (13). VR was measured before anastomosis of the graft, calculated from the relationship between pressure and flow in the outflow artery during infusion of the patient's own blood at a constant rate. VR was measured before and after vasodilation with papaverine. Primary graft patency at 30 days was documented. In the 10 limbs in which graft thrombosis occurred, VR was 1167 +/- 367 mPRU, significantly higher than VR in 57 limbs with a patent graft, 850 +/- 310 mPRU (P = 0.02, Mann-Whitney U test). After papaverine, VR was 823 +/- 368 mPRU in the limbs with a thrombosed graft, significantly higher than that of limbs with a patent graft, 463 +/- 211 mPRU (P = 0.001). VR appeared to show most promise as a predictor of early thrombosis in the group of femoro-tibial and femoro-peroneal grafts. In this group, the value of 800 mPRU after papaverine was 92% efficient and was 80% sensitive, 100% specific and had a predictive value of 100% for early thrombosis. Distal outflow VR is an important factor in early graft thrombosis and might have a practical application as a predictor of early thrombosis of femoro-distal bypass grafts.

The artificial sphincter AS800 in congenital urinary incontinence

The artificial urinary sphincter AS800 was implanted in 33 male and 13 female patients with congenital urinary tract incontinence. In 15 patients (32 per cent) previous operations to correct incontinence had failed. The sphincter was implanted around the bladder neck in 43 patients and around the bulbous urethra in 3. Mean patient age at the time of sphincter implantation was 13 years. In 40 patients (87 per cent) the sphincter functions well after a mean followup of 25 months and 39 patients (85 per cent) have satisfactory continence. In 6 patients the sphincter was removed because urethral, vulvar or scrotal erosions developed, all of whom had had previous surgical procedures in the area of the erosion. In 1 patient not operated upon previously erosion of the bulbous urethra developed. He did well after a new sphincter was implanted around the bladder neck. Five patients required an enterocystoplasty to achieve continence following the sphincter implantation. Nine patients required surgical revision of the sphincter for mechanical failure, technical errors, trauma and patient growth. We conclude that in patients with neurogenic sphincter failure implantation of an artificial sphincter around the bladder neck should be considered as the initial treatment of choice.

A correlation between the Geriatric Depression Scale long and short forms

A sample of 81 elderly subjects (M age = 76 years) volunteered to take part in a study to determine whether the Geriatric Depression Scale (GDS) Short Form is an acceptable substitute for the GDS Long Form. Half of the subjects took the GDS Long Form first, and half took the GDS Short Form first. After two weeks, the subjects were given the remaining form. Although the mean scores were lower than in previous correlation studies, the results indicated that the GDS Short Form correlated significantly (r = +.66, p less than .01) with the GDS Long Form, but not highly enough to be considered an appropriate substitute.

Does exposure of preovulatory oocytes to ultrasonic radiation affect reproductive performance?

Ultrasonography of preovulatory oocytes has been reported to lead to reduced litter size in rats. Because of the growing popularity of ultrasound-guided follicular aspiration in human in vitro fertilization programs, further study of ultrasonic radiation's effect on the preovulatory oocyte is warranted. We used 106 virgin Sprague-Dawley rats which, on the evening of proestrus, received ultrasonic radiation of sham treatment after the onset of the luteinizing hormone (LH) surge. No differences were found between control (C) and experimental (US) animals in pregnancy rate, number of corpora lutea, implantations, pups, and mean pup and placental weights at autopsy on day 22 of pregnancy. Ultrasonic radiation applied to meiotically active, preovulatory oocytes did not affect the reproductive performance of these rats.

Determinants of VA utilization. The 1983 survey of aging veterans

By the end of the decade, fully one half of American males aged 65 years and over will be veterans. In anticipation of the increased demand for medical services, the Veterans Administration recently commissioned a survey of the needs of aging veterans. From a national probability sample, approximately 34,500 households were screened to yield interviews with 3,013 veterans aged 55 years and over. Using multivariate regression analyses, the present study employed this data set for two purposes: 1) to identify covariates of past and present service utilization in the VA system, and 2) to identify the conditions under which veterans will declare an intention to use VA services in the future. Independent variables included medical diagnoses, ADLs, demographic and background characteristics, convenience and proximity to VA facilities, alternative forms of insurance coverage, VA eligibility, and attitudes about the quality of VA care. The results suggest markedly different predictors for current use versus likelihood of future use; however, income was related to both current and intended future utilization. The implications of these findings for policy development and utilization projections are discussed.

Extramammary Paget's disease. A critical reexamination

Fifty-five patients with extramammary Paget's disease were the source of material for this study. Step-sections were done through most of the specimens. Clinical information, including follow-up, was obtained on 45 of the 55 patients. Extramammary Paget's disease could be divided histologically according to where Paget cells were found, namely: 1) wholly within the epidermis and the epithelial structures of adnexa, and the dermis; 3) within the epidermis, the epithelial structures of adnexa, and contiguous epithelia of other organs such as the genitourinary and gastrointestinal tracts. Our conclusions are that extramammary Paget's disease is more than one disease and in most instances begins in the epidermis as an adenocardinoma and extends from there into contiguous epithelium of hair follicles and eccrine sweat ducts. Uncommonly, Paget cells extend from the epidermis into the dermis and from there may metastasize. Rarely, extramammary Paget's disease results from direct extension into the skin of an adenocarcinoma in a contiguous organ such as the genitourinary or gastrointestinal tract.