Host genetics as a cause of overdispersion of parasites among hosts: how general a phenomenon?

In the white-footed mouse, Peromyscus leucopus, the tapeworm Hymenolepis citelli occurs at low (2-3%) prevalence in the field. We found that mature infections (i.e., with egg production) developed in up to 100% of hosts. In the laboratory, a majority of hosts lost their infection by 28 days postintubation. In wild mice infected in the laboratory and returned to the field, infections were more prolonged, with half of the mice still infected at 100 days postintubation. A majority of previously infected hosts resisted challenge infection. Our introduction of laboratory-infected mice into a natural population of hosts appeared to cause infections among previously uninfected mice, leading to an increase in the prevalence of tapeworm infection among mice not intubated. Although genetically based expulsion of tapeworms before maturity is important in causing low prevalence in a similar host-parasite system, such resistance cannot explain low prevalence in the present system. It appears that both heterogeneous distribution and rarity of intermediate hosts as well as short parasite lifespan contribute to low prevalence and overdispersion. Host-parasite dynamics of 2 very similar systems appear to differ markedly.

Regulation of collagen production by medial smooth muscle cells in hypoxic pulmonary hypertension

Pulmonary hypertension is associated with abnormal connective tissue deposition in the media of pulmonary arteries. Lobar arteries from calves maintained for up to 15 days at simulated high altitude showed a 35% increase in collagen and a greater than 40% increase in crosslinked elastin per microgram protein. Labeling of artery tissue with [14C]proline revealed a nearly twofold increase in relative collagen synthesis. There was increased incorporation into Types I, III, IV, and V collagen with an increase in the proportion of newly synthesized Type IV collagen. Quantitation of collagen mRNA by slot-blot assay demonstrated increased levels of Types I and IV collagen message. In addition, medial smooth muscle cells isolated from the hypertensive calves demonstrated a nearly twofold increase in relative collagen synthesis, a twofold increase in the accumulation of newly synthesized collagen per microgram DNA, and increased levels of Types I and IV collagen mRNA. Exposure of pulmonary artery smooth muscle cells, adventitial cells, and fetal calf ligament fibroblasts to conditioned calf serum harvested from cultures of medial cells from hypertensive animals increased their levels of collagen as well as elastin mRNA. These studies suggest that the increased production of collagen in hypertensive arteries is mediated at a pre-translational level by soluble factor(s) generated by medial smooth muscle cells.

Purification and biochemical characterization of CP4 (SP-D), a collagenous surfactant-associated protein

CP4 is a collagenous glycoprotein (43 kDa, reduced) synthesized by rat type II pulmonary epithelial cells in primary culture (Persson et al., 1988). In order to better characterize this protein, CP4 was isolated from rat bronchoalveolar lavage and EDTA extracts of lung surfactant by adsorption to barium sulfate and elution with sodium citrate followed by reverse-phase HPLC. Amino acid analysis of purified CP4 demonstrated 4-hydroxyproline (Hyp), hydroxylysine (Hyl), and acid-labile components coeluting with Hyl glycosides. In addition, gas-phase amino-terminal microsequencing of two CP4 CNBr peptides demonstrated nonoverlapping collagenous sequences comprised of nine and six Gly-X-Y triplets, containing a total of four residues of Hyp and two of Hyl. There was less than 50% sequence homology of these peptides with the cDNA-derived sequence of the collagenous domain of rat SP-A. Two-dimensional IEF/SDS-PAGE resolved the protein into a charge train of basic isoforms (pI approximately 6-8), similar to those of newly synthesized CP4 and the class D surfactant proteins (Phelps & Taeusch, 1985). Gel filtration of nondenatured CP4 on 4% agarose showed a high apparent molecular mass complex comprised of disulfide-bonded trimers of the 43-kDa subunits. Antibodies to purified lavage CP4 showed specific binding to newly synthesized and surfactant-associated CP4. We propose that CP4 be designated "surfactant protein D" (SP-D) in accordance with an accepted nomenclature for surfactant-associated proteins.

Isolation and characterization of bovine pancreastatin

Bovine pancreastatin, a 47 amino acid residue peptide, was isolated from the pancreas and the pituitary gland using a chemical method which detects its C-terminal glycine amide structure. The complete amino acid sequence of the pancreatic peptide is 74% homologous to that of porcine pancreastatin and is identical to bovine chromogranin A-(248-294), as deduced from its cDNA sequence. The sequence of the first 28 amino-terminal residues of the pituitary peptide was determined to be identical to the corresponding sequence of the pancreatic peptide. Since the pituitary peptide also contains the C-terminal glycine amide, it is therefore likely to be identical in structure to the pancreatic peptide. Thus, we conclude that bovine chromogranin A is the precursor of bovine pancreastatin. Synthetic bovine pancreastatin inhibited pancreatic exocrine secretion in a similar manner to porcine pancreastatin.

CP4: a pneumocyte-derived collagenous surfactant-associated protein. Evidence for heterogeneity of collagenous surfactant proteins

Type II pneumocytes secrete pulmonary surfactant and are known to synthesize SP-35, a collagenous surfactant-associated protein. Freshly isolated type II cells also synthesize other bacterial collagenase-sensitive and hydroxyproline-containing proteins, including a glycoprotein designated CP4. CP4 was isolated from rat pneumocyte culture medium by immune precipitation with polyclonal antibodies to rat surfactant proteins or by DEAE chromatography and reverse-phase or gel permeation HPLC. CP4 did not cross-react with polyclonal antibodies to SP-35 and was completely resolved from SP-35 by SDS-PAGE (Mr 43K reduced) or isoelectric focusing. Unlike SP-35, which consists of acidic isoforms assembled as disulfide-bonded dimers and multimers, CP4 was secreted as basic isoforms assembled as disulfide-bonded trimers. Differences in primary structure were demonstrated by CNBr and V8 protease peptide mapping. The secretion of both proteins was inhibited by 2,2'-dipyridyl, an inhibitor of posttranslational prolyl and lysyl hydroxylation and collagen triple helix formation. CP4 was isolated from EDTA extracts of rat surfactant. These studies provide evidence for the heterogeneity of pneumocyte-derived collagenous surfactant-associated proteins.

Digitonin-permeabilized colonic cell layers. Demonstration of calcium-activated basolateral K+ and Cl- conductances

Sheets of isolated turtle colon were exposed to digitonin on the mucosal side to chemically remove the apical membrane as a permeability barrier. Increases in the mucosal uptake of 86Rb, [3H]mannitol, and 45Ca-EGTA, and the appearance of the cytosolic marker enzyme lactate dehydrogenase in the mucosal bath confirmed the permeabilizing effect of the detergent. Basolateral K+ and Cl- currents were generated by imposing transmural ion gradients, and cytosolic free Ca2+ was manipulated by means of a Ca2+-EGTA buffer system in the mucosal bathing solution. Raising the cytosolic free Ca2+ concentration from the nanomolar to the micromolar range activated basolateral conductances for K+ and Cl-. Differences in ion selectivity, blocker specificity, calcium activation kinetics, and divalent cation activation selectivity indicated that the Ca2+-induced increases in the K+ and Cl- conductances were due to separate populations of channels. The results are consistent with the notion that the apical membranes of turtle colon epithelial cells can be functionally removed under conditions that preserve some of the conductive properties of the basolateral membrane, specifically Ca2+-activated conductive pathways for K+ and Cl-. This permeabilized preparation should offer a means for the identification of macroscopic currents that are due to presumed Ca2+-activated channels, and may also provide a model system for the functional reconstitution of channel regulatory mechanisms.

Effects of CRF and ANG II on ACTH and vasopressin release in conscious dogs

The aim of the present study was to examine the effects of corticotropin-releasing factor (CRF) in conscious dogs and to determine whether the stimulation of adrenocorticotropic hormone (ACTH) release by angiotensin II (ANG II) results from potentiation of the action of CRF. In addition, the possible role of CRF in the stimulation of vasopressin released by ANG II was investigated. The following experiments were performed: 1) intravenous saline infusion; 2) ANG II (10 ng.kg-1.min-1) alone; 3) vasopressin (1 ng.kg-1.min-1) alone; 4) CRF (0.001, 0.01, or 0.1 microgram/kg iv) bolus; 5) vasopressin (1 ng.kg-1.min-1) and CRF (0.1 microgram/kg) together; 6) CRF (0.001, 0.01, or 0.1 microgram/kg) and ANG II (10 ng.kg-1.min-1) together; 7) ANG II (10 ng.kg-1.min-1) followed 15 min later with CRF (0.001, 0.01, or 0.1 microgram/kg). Each dose of CRF was tested on a different day. Infusion of ANG II alone stimulated the release of ACTH, cortisol, and vasopressin. Administration of CRF produced dose-dependent increases in plasma ACTH and cortisol concentrations, and the highest dose of CRF increased plasma vasopressin concentration. CRF given together with ANG II did not potentiate the stimulation of ACTH release by CRF. Vasopressin at the dose tested did not stimulate ACTH release but potentiated the ACTH response to CRF. ANG II stimulated vasopressin release but did not potentiate the AVP response to CRF. These results show that, in conscious dogs, ANG II and CRF each increase plasma ACTH concentration and that the ACTH response to CRF is potentiated by vasopressin but not by ANG II.(ABSTRACT TRUNCATED AT 250 WORDS)

A sensitive radioimmunoassay for somatomedin-C/insulin-like growth-factor I based on synthetic insulin-like growth factor 57-70

We have developed a region-specific radioimmunoassay for somatomedin-C/insulin-like growth factor-I (IGF-I) directed against IGF-I 57-70. This sequence includes part of the A region and all of the carboxyterminal D region. In addition to being highly specific, this immunoassay is sensitive to as little as 1 ng/ml of IGF-I, and has half-maximum displacement by 10 ng/ml of IGF-I. Comparison to other existent immunoassays for IGF-I shows correlation coefficients of greater than 0.95. This immunoassay has the advantage of being directed against a known region of the IGF-I molecule which is on the exterior of the 3-dimensional structure, and can use a readily available synthetic peptide as both radioligand and standard.

Solitary non-parasitic liver cyst treated by cyst-gastrostomy

A 66 year old female presented with a symptomatic solitary non-parasitic liver cyst. This was treated by a cyst-gastrostomy following which the patient has remained well without complications for 12 years. Given an appropriate anatomical relationship of cyst and stomach, this would appear to be a safe and effective operation.

Effect of vasopressin blockade on blood pressure during water deprivation in intact and baroreceptor-denervated conscious dogs

Previous studies have provided evidence that vasopressin plays an important role in blood pressure regulation during water deprivation. However, these investigations have been complicated by reflex compensatory increases in cardiac output and renin secretion. The aim of the present study was to investigate the effect of blockade of the vasoconstrictor action of vasopressin in conscious water-deprived dogs in which the low- and/or high-pressure baroreceptors were denervated to minimize reflex responses. Vasopressin blockade in sham-operated dogs (n = 7) did not change arterial pressure. Heart rate rose from 78 +/- 9 to 119 +/- 13 beats/min (P less than 0.01), and plasma renin activity increased from 10.9 +/- 2.1 to 21.6 +/- 4.6 ng.ml-1.3 h-1 (P less than 0.01). In carotid sinus-denervated dogs (n = 6), vasopressin blockade again failed to decrease arterial pressure. Heart rate increased from 105 +/- 10 to 132 +/- 10 beats/min (P less than 0.01), and plasma renin activity rose from 6.8 +/- 1.7 to 15.5 +/- 2.4 ng.ml-1.3 h-1 (P less than 0.01). The antagonist also failed to change blood pressure in cardiac-denervated dogs (n = 5). Heart rate increased from 111 +/- 9 to 119 +/- 1 beats/min (P less than 0.01), but plasma renin activity did not increase significantly. In marked contrast, vasopressin blockade in sinoaortic/cardiac-denervated dogs (n = 7) promptly decreased arterial pressure from 115 +/- 8 to 94 +/- 7 mmHg (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Women's health and social change: the case of lay midwives

One reaction to the medicalization of birth has been the comeback of lay midwives in the past 10 years. While many practice alone as did midwives 80 years ago, now midwives are networking and organizing in regional and statewide groups, an important new distinction in the light of increasing regulatory policy formation by many states. Are these groups the beginnings of traditional bureaucratic health professional organizations or are they better described as alternative women's health groups that espouse nonhierarchical philosophies of women's health? In this article, we describe an empirical study of one such group, the Michigan Midwives' Association, and explore the philosophies and practices of individual members as well as the internal organization of the group and its influence on members. Data were collected using individual telephone interviews with 48 of 50 members, group newsletters and documents, and two spokespersons who developed an oral history of the Association since its origin in 1978. Results suggest that the group plays an important role in reinforcing individually held philosophies about women-controlled birth and in providing social support to health workers practicing outside the traditional system.

Pancreatic enzymes in patients with end-stage renal disease maintained on hemodialysis

We determined serum levels of total amylase, amylase isoenzymes, and lipase in a group of 34 asymptomatic patients with end-stage renal disease (ESRD) before and after hemodialysis. In addition, one ESRD patient was studied during an episode of acute pancreatitis. We also determined amylase activity in the saliva. The results were compared with those obtained in a group of 19 normal individuals. Predialysis serum total amylase activity in the 34 asymptomatic ESRD patients was significantly greater than that found in the control group, and remained unchanged after hemodialysis. Serum lipase activity in the 34 asymptomatic ESRD patients was significantly increased before hemodialysis, and rose further after hemodialysis. The observed rise in serum lipase activity correlated with the cumulative dose of heparin given during dialysis. None of the 34 asymptomatic ESRD patients showed a discernible P3 isoamylase band, despite elevation of serum total amylase level. In contrast, the patient with acute pancreatitis exhibited a marked rise in serum P3 isoamylase (14-17%), along with a marked and transient rise in serum total amylase and lipase above their elevated baseline values. Interestingly, the amylase content of saliva in the ESRD patients was significantly lower than that found in the control group. In conclusion, ESRD patients exhibit a marked elevation of serum amylase and lipase levels in the absence of clinical pancreatitis. The observed hyperamylasemia is not associated with increased P3 isoamylase level unless pancreatitis is present. Furthermore, serum lipase rises with hemodialysis, presumably because of the lipolytic effect of heparin used during this procedure. Accordingly, serum sample for lipase determination should be obtained before dialysis.

Vascular endothelial cells and granulopoiesis: interleukin-1 stimulates release of G-CSF and GM-CSF

Cultured mononuclear phagocytes produce soluble factors that stimulate endothelial cells to release GM-colony-stimulating activity (GM-CSA). One such factor was recently identified as interleukin 1 (IL 1). Studies were designed to determine which types of granulopoietic factors are released by IL 1-stimulated endothelial cells. Supernatants from endothelial cells cultured for 3 days in medium containing IL 1 alpha and beta were tested in both murine and human CFU-GM colony growth assays. The effect of conditioned media on differentiation of WEHI-3B myelomonocytic leukemic cells was also examined. Control media containing IL 1 alone or unstimulated endothelial cell-conditioned media contained no detectable CSA in any bioassay. Medium conditioned by IL 1-stimulated endothelial cells stimulated the clonal growth of both human and murine CFU-GM and induced macrophage differentiation of WEHI-3B cells. Treatment of these conditioned media with a highly specific neutralizing monoclonal G-CSF antibody completely inhibited their activity in the murine CFU-GM assay, but only partially inhibited GM colony growth by human marrow. Treatment of the active conditioned media with a neutralizing rabbit anti-human GM-CSF antibody partially reduced the activity of the media in the human GM-colony growth assay. G-CSF radioimmunoassay of endothelial cell culture supernatants and Northern blot analysis of endothelial cell cytoplasmic RNA for GM-CSF gene transcripts confirmed that IL 1 induced expression of both G-CSF and GM-CSF genes. Because treatment of media with both antibodies abrogated all activity in the human GM colony growth assay, we conclude that IL 1-stimulated endothelial cells release both G and GM-CSF and that these are the only granulopoietic factors detectable in clonogenic assays released by these cells in vitro.

Calcium: a program in BASIC for calculating the composition of solutions with specified free concentrations of calcium, magnesium and other divalent cations

A BASIC program is presented which facilitates the formulation of biologically relevant chemical solutions containing specified free concentrations of as many as three divalent metal cations (Ca2+, Mg2+ and the choice of a third divalent cation) at any pH in the presence of as many as three ligands (EGTA, ATP and GTP). The program uses the law of mass action and the absolute stability (association) constants found in the literature to calculate the total concentration of divalent metal cation needed to achieve a desired free concentration. The user enters the pH, the concentrations of the ligands used and the desired free concentrations of the divalent cations. This program was developed for use in a wide range of biological applications, particularly the rapid design of solutions which mimic certain aspects of intracellular fluid.

Quantitation of ceftetrame in human plasma and urine by high-performance liquid chromatography

A method is described for quantifying ceftetrame, the acid metabolite of methylene (6R,7R)-7-[(Z)-2-(2-amino-4-thiazolyl)-2-(methoxyimino)acetamido]-3- [(5-methyl-2H-tetrazol-2-yl)-methyl]-8-oxo-5-thia-1-azabicyclo[4.2 .0]oct-2-ene-2-carboxylate pivalate, an orally active cephalosporin. Sodium benzylpenicillin is added to the plasma as the reference standard. The compounds are extracted from plasma or urine using a Bond Elut phenyl column. An aliquot of the methanol eluate is analyzed by high-performance liquid chromatography using a Waters Nova-Pak phenyl column and a UV detector set to 225 nm. The ratios of the peak heights for ceftetrame and sodium benzylpenicillin are calculated and converted to concentrations of analyte with calibration curves that are generated from the analysis of analyte-free plasma or urine fortified with various amounts of ceftetrame and a fixed amount of sodium benzylpenicillin. For plasma, the limit of quantitation for the assay is 0.48 microgram/ml and the inter-assay precision (relative standard deviation) is 9.3%. For urine, the limit of quantitation for the assay is 19.1 micrograms/ml, and the inter-assay precision is 4.9%.

Antiserum developed for the E peptide region of insulin-like growth factor IA prohormone recognizes a serum protein by both immunoblot and radioimmunoassay

Nucleotide sequencing of the two known cDNAs encoding human insulin-like growth factor I (IGF-I) predicts two different prohormone forms of IGF-I. The predicted prohormone amino acid sequences (E peptide regions) extend the carboxy-terminus of IGF-I by either an additional 35 (IGF-IA) or 77 (IGF-IB) amino acids. We developed an antiserum directed against a synthetic peptide which is unique to the E peptide region of IGF-IA prohormone. In a RIA using this antiserum, synthetic E peptide immunoreactivity was found in the serum of patients with chronic renal failure. The protein recognized by this antiserum has a mol wt of about 13,000 by neutral gel filtration and about 19,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. These data suggest that the E peptide region of the IGF-IA prohormone is expressed and circulates as part of the prohormone.

Pancreastatin and islet hormone release

The effect of pancreastatin on the release of insulin, glucagon, and somatostatin was studied in the isolated perfused rat pancreas. After an initial equilibration period (-20 to 0 min) with a basal glucose concentration (3.3 mM), the pancreata were perfused with either 16.7 mM glucose (0-40 min) or with 20 mM arginine (0-20 min). Pancreastatin was introduced 10 min prior to and throughout the administration of the high glucose and arginine and continued during their perfusion. As expected, the glucose and the arginine augmented insulin and somatostatin release. Pancreastatin (1 and 10 nM) markedly suppressed the first phase of insulin release with both insulinogogues used, while the early somatostatin secretion was not significantly decreased. However, the peak incremental somatostatin response to arginine was reduced by 50% (P less than 0.05). Conversely, the peptide (10 nM) tended to augment arginine-induced glucagon release. Pancreastatin (100 nM) also suppressed glucose-stimulated insulin release from isolated rat islets. These pancreastatin-mediated alterations in islet hormone release are reminiscent of those known to characterize non-insulin-dependent diabetes. Therefore, the significance of pancreastatin in islet physiology and pathophysiology deserves special consideration.