Mathematical analysis of transport and exchange in skeletal muscle

A new approach to modelling microcirculatory transport and exchange is introduced and developed with specific reference to skeletal muscle. The objective is to describe the large-scale interaction of a great number of differently perfused capillary groups and to interpret phenomena observed in a whole organ in terms of processes occurring within individual capillaries. We consider fluid exchange and the associated macromolecular transport, the exchange of small metabolites carried in the plasma, and oxygen transport to tissue.

The influence of histamine at various concentrations on the cell cycle state of hematopoietic stem cells (CFU-s)

The influence of histamine at various concentrations on the cell cycle state of hematopoietic stem cells (CFU-s) was investigated. CFU-s were triggered from the G0 state into the S phase of the cell cycle by in vitro treatment of mouse bone marrow cells with high concentrations of histamine. This effect could be antagonized by a histamine H2 receptor blocking agent. When bone marrow cells were treated with a histamine H1 receptor antagonist prior to histamine treatment, low concentrations of histamine also triggered the entrance of CFU-s into the DNA synthetic phase. Our findings further suggest the existence of histamine H1 and H2 receptors on the surface of CFU-s cells and the antagonistic effect of these two histamine receptor subtypes on the cell cycle state of CFU-s. Our results also suggest that histamine may participate in regulating the proliferation of hematopoietic stem cells in vivo during immune or inflammatory responses.

Role of domain II of Pseudomonas exotoxin in the secretion of proteins into the periplasm and medium by Escherichia coli

Pseudomonas exotoxin (PE) is composed of structural domains I, II, and III; when interacting with mammalian cells the function of domain I is cell recognition, the function of domain II is membrane translocation, and domain III functions in ADP ribosylation. PE is secreted by Pseudomonas aeruginosa into its growth medium. The domain responsible for secretion has been examined by expressing modified PE genes in Escherichia coli under the control of a T7 promoter. Without a signal sequence, PE accumulates within the cell, but PE is secreted into the periplasm when part or all of domain I is removed. PE appears in the periplasm and medium when domain I and part of domain II are removed. Domain II alone is secreted into the periplasm, whereas domain III alone remains within the cell. Addition of an OmpA signal sequence results in secretion of mature PE into the periplasm and secretion of domains II-III into the medium. A protein composed of transforming growth factor alpha fused to the amino terminus of domains II-III is secreted into the periplasm without a signal sequence and into the medium with a signal sequence. A protein composed of domain(s) II or II-III fused to the amino terminus of alkaline phosphatase is secreted into the periplasm and the medium with or without a signal sequence. We conclude that domain II contains important information for protein secretion.

The effect of berbamine derivatives on activated Ca2+-stimulated Mg2+-dependent ATPase in erythrocyte membranes

Ca2+-stimulated Mg2+-dependent ATPase (Ca2+ + Mg2+-ATPase) stimulated by calmodulin, by partial proteolysis or by oleic acid in erythrocyte membranes was inhibited by various derivatives of the naturally occurring alkaloid berbamine. The ability of these derivatives to inhibit trypsin-activated Ca2+ + Mg2+-ATPase correlated well with their ability to inhibit the calmodulin-stimulated enzyme. Inhibition of the trypsin-activated Ca2+ + Mg2+-ATPase by O-4-(ethoxybutyl)berbamine (EBB) was competitive with respect to ATP. The Ki for inhibition was about 8 microM. These results suggest that the binding site of EBB on the activated Ca2+ + Mg2+-ATPase may bear structural similarity to that on calmodulin, and may be closely related to the ATP-binding site on the enzyme.

Comparison of the effects of 4-methylhistamine on the cell-cycle response between CFU-s and its subpopulation

When bone marrow cells were treated with an H2-receptor agonist (4-methylhistamine 10(-8) M) before treatment with hydroxyurea (10(-3) M), the suicide rate of spleen colony-forming units (CFU-s) as a whole rose significantly. The rabbit antimouse brain serum (RAMBS)-resistant CFU-s subpopulation was also significantly elevated. Prior treatment of bone marrow cells with cimetidine would prevent this effect of 4-methylhistamine (4-MH). These findings not only confirm that 4-MH can trigger mouse bone marrow CFU-s to enter a DNA synthetic phase of the cell cycle, but also suggest that the RAMBS-resistant CFU-s subpopulation is more sensitive to the effect of 4-MH. Furthermore, this suggests that concentrations of the histamine receptor change during the developmental process of CFU-s.

Preferential binding of androgen to transcriptionally active chromatin in rat prostate

Rat ventral prostate chromatin was fractionated by the Micrococcal nuclease procedure of Berkowitz and Riggs (Biochemistry 20, 7284-7290, 1981). Four chromatin fractions were obtained and analyzed by gel electrophoresis for their protein and DNA components, by hybridization of their DNAs with an androgen regulated cDNA for transcribed DNA sequence, and by [3H]dihydrotestosterone exchange assay and steroid competition experiment for specific androgen binding. All four chromatin fractions contained a complete complement of histones and DNA in multiples of about 200 base pairs, indicating repeating nucleosome structure. The active chromatin fraction, which has the shortest nucleosome repeats of 186 basepairs, was enriched in the androgen regulated sequence and bound androgen. These results correlate androgen binding sites with transcribed DNA sequence and structurally distinctive domain of chromatin in the rat prostate.

A derivative of bisbenzylisoquinoline alkaloid is a new and potential calmodulin antagonist

A new derivative of bisbenzylisoquinoline (berbamine type): 0-(4-ethoxylbutyl) berbamine (EBB) was found to possess powerful and specific calmodulin (CaM) inhibitory properties. It inhibited CaM-stimulated Ca2+-Mg2+-ATPase in human erythrocyte membrane with IC50 value of 0.35 microM compared to that of 60 microM of berbamine. CaM-independent basal Ca2+-Mg2+-ATPase, Na+-K+-ATPase and Mg2+-ATPase were not effect at 1.0 microM of EBB at which CaM-dependent Ca2+-Mg2+-ATPase was already potently inhibited. The inhibition of CaM-dependent Ca2+-Mg2+-ATPase was competitive with respect to CaM. Higher amount of CaM reversed the inhibition caused by higher concentration of EBB. Using dansyl-CaM (D-CaM), it was shown that EBB binds directly to CaM and caused a conformational change of CaM polypeptide chain. From fluorescence titration curve we obtained evidence that in the presence of Ca2+, CaM has two specific binding sites for EBB and additional unspecific binding sites. The Ca2+-dependent binding sites of EBB on CaM were novel region different from the binding sites for TFP.

Characterization of the androgen-dependent 22Kdalton glycoprotein from rat ventral prostate

Oxidation by molecular oxygen converted the 22Kdalton glycoprotein from rat ventral prostate into a 34K species and this reaction could be reversed by thiol reducing reagent. Measurement of the level of the 22Kdalton glycoprotein in prostatic cytosol by the radial immunodiffusion technique showed that changes in the 22Kdalton glycoprotein concentration in response to androgen withdrawal and replacement were slow in comparison to androgen regulated levels of mRNA coding for the protein. (3) Charcoal absorption steroid binding assays of the 22Kdalton glycoprotein revealed that the protein did not bind testosterone, estradiol, progesterone or corticosterone. These results indicate that the 22Kdalton glycoprotein is metabolically stable, not steroid-binding, and exists as an oligomer through disulfide crosslinking.

'Northern Cross' hybridization for rapid identification of exon-containing restriction fragments

The Northern Cross method allows direct comparison of restriction digests of cDNA and genomic clones to RNA populations by a specialized form of hybridization. This technique is based on the use of Northern and Southern blotting techniques and requires the use of two nylon membranes of differing chemical characteristics. A nylon membrane containing permanently affixed, electrophoretically fractionated RNAs is contact-hybridized at a right angle to a second, chemically different nylon membrane containing transiently bound, fractionated labeled DNA fragments. RNA and DNA bands possessing homology will hybridize where they cross, forming an autoradiographically detectable spot. This Northern Cross procedure proportionately represents the amounts of different RNAs derived from a particular sequence in a manner similar to what would have been observed in a Northern blot. This method, which can be used in the analysis of even relatively rare RNA species, permits rapid and fairly inexpensive identification of exon-containing fragments or determination of the relationship between related, multiple RNA species.

Translocation chromosome 7 of A431 cells contains amplification and rearrangement of EGF receptor gene responsible for production of variant mRNA

The epidermal growth factor (EGF) receptor, along with several oncogene protein products, possesses tyrosine-specific protein kinase activity. Furthermore, the EGF receptor has structural similarity to the putitive v-erb-B transforming protein. Because of these closely shared characteristics, it is important to elucidate the possible involvement of the EGF receptor in malignant transformation. The epidermal carcinoma cell line A431 exhibits an abnormally high number of EGF receptors, which is associated with the presence of translocation chromosome M4. Recently, A431 cells have been shown to contain amplified sequences for the EGF receptor gene(s) and also to produce a variant mRNA which diverges from the normal EGF receptor mRNA at the 3' end. Here we report, using the human EGF receptor cDNA probe pE7, that the chromosome M4 has a six- to sevenfold amplification of the EGF receptor gene. Furthermore, the presence of M4 in somatic cell hybrids correlates with the production of the variant 2.9-kb mRNA. This aberrant mRNA is apparently generated by an intrachromosomal rearrangement which was detected using as a probe a fragment of the pE15cDNA encoding the variant mRNA.

The effects of lead ion on immune function of rabbit alveolar macrophages: quantitation of immune phagocytosis and rosette formation by 51Cr in vitro

Experiments by a 51Cr-labeling technique were performed to investigate the effects of lead (Pb2+) on immune phagocytosis and Fc-rosette formation of rabbit pulmonary alveolar macrophages (PAMs). Evidence is presented that Pb2+ at concentrations of 10(-3) and 10(-4)M could inhibit these functions of PAMs. The degree of inhibition corresponded to the concentration of this heavy metal ion in vitro.

Membranous obstruction of the inferior vena cava in the United States

The pathogenesis of membranous obstruction of the inferior vena cava (MOVC) is unclear. Although the lesion is rare in the United States compared to Japan, India, and black South Africa, it has been responsible for 23% of cases of hepatic outflow obstruction we have encountered in the ethnically heterogeneous indigent population of Los Angeles. Most patients with MOVC are male. In contrast, recent series of patients with Budd-Chiari Syndrome (BCS) have demonstrated a female predominance. Compared to BCS without involvement of the inferior vena cava (IVC), patients with MOVC have more chronic symptoms. Large truncal collaterals, particularly on the back, strongly suggest MOVC. In patients without this sign, a high index of diagnostic suspicion is required. Chronic hepatitis B infection occurs with increased frequency in these patients. Chest radiograph may show an enlarged azygous shadow. Liver-spleen scan is not helpful, and the liver biopsy is frequently nondiagnostic. A useful screening procedure for hepatic outflow block is transhepatic portal pressure measurement demonstrating aberrant hepatic veins with pressures higher than in the portal vein and, occasionally, hepatofugal portal flow. Transcardiac membranotomy appears to be symptomatically effective in patients with MOVC and at least one patent hepatic vein. It is not known whether this operation will prolong life and prevent the development of hepatocellular cancer, which may occur in up to 48% of these patients. The correct therapeutic approach has not been established for those patients whose lesion is not amenable to surgery because of extensive IVC occlusion or absence of patent hepatic veins.

Elevated epidermal growth factor receptor gene copy number and expression in a squamous carcinoma cell line

The human epidermal growth factor (EGF) receptor is known to be homologous to the v-erb B oncogene protein of the avian erythroblastosis virus. Overexpression of the EGF receptor gene in A431 epidermoid carcinoma cells is due to gene amplification. In this study, a variety of squamous cell carcinomas were examined and one, SCC-15, contained high levels of the EGF receptor as determined by immunoprecipitation via an EGF receptor-specific polyclonal antibody. Using a cloned EGF receptor complementary DNA as a probe, the level of EGF receptor RNA was found to be elevated four-fold in SCC-15 relative to normal cultured keratinocytes. When the same probe was used to identify EGF receptor gene fragments on a genomic DNA blot, the SCC-15 cell line was shown to possess an EGF receptor gene copy number amplified four to five times. Gene amplification results in the enhancement in the level of the EGF receptor in several carcinomas and could be responsible for the appearance of the transformed phenotype in these cells.

Characterization of epidermal growth factor receptor gene expression in malignant and normal human cell lines

To investigate the possibility that the epidermal growth factor (EGF) receptor functions as an oncogene product, we have determined the levels of EGF receptor protein and RNA in a variety of malignant and normal human cells, using a specific polyclonal antibody to the EGF receptor and a cDNA clone (plasmid pE7) that encodes the EGF receptor, respectively. Besides A431 epidermoid carcinoma cells, which are known to make large amounts of EGF receptor, cell lines from two ovarian cancers, two cervical cancers, and one kidney cancer were found to contain substantial amounts of receptor protein (11-22% of A431). Normal human fibroblasts (Detroit 551), a human lymphocyte line (IM-9), and a leukemic lymphocyte line (CEM) contained low or undetectable levels of EGF receptor. RNA blot analysis showed that among the human cell lines examined the levels of a 10- and a 5.6-kilobase species of pE7-specific RNA generally correlated with the amount of the EGF receptor protein. Genomic DNA blot analysis revealed that except for A431 none of these cell lines expressing high levels of EGF receptor protein possessed amplified receptor gene sequences. A431 cells are known to secrete a truncated form of the EGF receptor. An abundant 2.9-kilobase RNA is found only in A431 cells; it could encode the truncated form of the EGF receptor.

Human epidermal growth factor receptor cDNA is homologous to a variety of RNAs overproduced in A431 carcinoma cells

The recently discovered similarity between the human epidermal growth factor (EGF) receptor and the avian erythroblastosis virus v-erb-B protein supports the hypothesis that viral oncogenes share a common evolutionary origin with genes encoding growth-regulating cell-surface receptors. To elucidate the relationship between receptors and malignant transformation, we have now used a fragment of v-erb-B as a probe to screen a cDNA library of mRNA from A431 human carcinoma cells, which possess a large number of EGF receptors. Of the six clones isolated, the largest (pE7) contains an insert of 2.4 kilobase pairs (kbp) whose deduced amino acid sequence is homologous to the v-erb-B protein and identical to reported EGF receptor peptide sequences. This pE7 cDNA hybridized to three prominent RNAs of approximately 10, 5.6 and 2.9 kilobases (kb), and to three minor species of 6.3, 4.6 and 3.3 kb. All were present in elevated levels in A431 cells. The prominent 2.9-kb RNA was homologous only to the 5' portion of the pE7 insert. This result raises the possibility that differential RNA processing is used by A431 cells to generate a variety of RNAs.

Amplification and enhanced expression of the epidermal growth factor receptor gene in A431 human carcinoma cells

The sequence of the human epidermal growth factor (EGF) receptor shows great homology with the avian erythroblastosis virus v-erb B oncogene, raising the possibility that the receptor gene is identical to the c-erb B protooncogene. Human A431 epidermoid carcinoma cells, which have an unusually high number of EGF receptors, were examined to determine whether elevated EGF receptor levels correlate with gene amplification. Southern blots of genomic DNA's from A431 and other human cell lines were probed with either a v-erb B gene fragment or a human EGF receptor complementary DNA clone (pE7), previously isolated from an A431 complementary DNA library. When either probe was used to analyze Eco RI- or Hind III-generated DNA fragments, EGF receptor DNA sequences were amplified about 30-fold in A431. Differences in the banding pattern of A431 DNA fragments relative to normal fibroblast DNA indicate the occurrence of a rearrangement in the region of the receptor gene. Furthermore, A431 cells contain a characteristic, prominent 2.9-kilobase RNA. These results are consistent with the hypothesis that, in A431 cells, gene amplification, possibly associated with a translocation event, may result in the overproduction of EGF receptor protein or the appearance of the transformed phenotype (or both).

Androgen regulation of nuclear poly(A) polymerase activities in rat ventral prostate

The existence of nucleoplasmic and chromatin bound forms of poly(A) polymerase in the rat ventral prostate has been demonstrated. The levels of the prostate chromatin and nucleoplasmic poly(A) polymerase activities appeared to be under the influence of testosterone. Castration reduced both free and bound prostatic poly(A) polymerase activities to 30% of the normal values. Administration of testosterone to castrated rat resulted in increases in both nuclear poly(A) polymerase activities at 2-4 h after androgen replacement. The results suggest that post-transcriptional processing is under androgenic control.

Identification of two cDNA clones coding for androgen-dependent polypeptides in rat ventral prostate

cDNA clones were obtained by transformation of E. coli chi 1776 with pBR322 containing insert of ds cDNA synthesized from total rat prostate poly(A)RNA. Two prostate-specific cDNA clones were isolated by colony hybridization and identified by message selection/translation as encoding polypeptides of Mr: 13,500 and 9,300. Hybridization of poly(A)RNA from normal and castrated rat prostates to the cloned cDNAs indicated that the levels of mRNAs coding for Mr: 13,500 and 9,300 polypeptides are regulated by testosterone.