Showing papers by "Baylor College of Medicine published in 1988"

Human systems as linguistic systems: preliminary and evolving ideas about the implications for clinical theory.

Abstract: From our earliest practice of family therapy at medical schools, private family therapy institutes, and public agencies, our work with difficult populations that do not respond to current treatment technologies has reminded us of the inadequacies of our theoretical descriptions and the limitations of our expertise. This work has influenced our current, evolving clinical theory as we move from thinking of human systems as social systems defined by social organization (role and structure) to thinking of them as distinguished on the basis of linguistic and communicative markers. Hence, for us, the social unit we work with in therapy is a linguistic system distinguished by those who are "in language" about a problem, rather than by arbitrary and predetermined concepts of social organization. We call the therapy system a problem-organizing, problem-dis-solving system.

Estrogen binding, receptor mRNA, and biologic response in osteoblast-like osteosarcoma cells

Abstract: High specific activity estradiol labeled with iodine-125 was used to detect approximately 200 saturable, high-affinity (dissociation constant approximately equal to 1.0 nM) nuclear binding sites in rat (ROS 17/2.8) and human (HOS TE85) clonal osteoblast-like osteosarcoma cells. Of the steroids tested, only testosterone exhibited significant cross-reactivity with estrogen binding. RNA blot analysis with a complementary DNA probe to the human estrogen receptor revealed putative receptor transcripts of 6 to 6.2 kilobases in both rat and human osteosarcoma cells. Type I procollagen and transforming growth factor-beta messenger RNA levels were enhanced in cultured human osteoblast-like cells treated with 1 nM estradiol. Thus, estrogen can act directly on osteoblasts by a receptor-mediated mechanism and thereby modulate the extracellular matrix and other proteins involved in the maintenance of skeletal mineralization and remodeling.

The Anatomic Basis of Femoral Component Design

Abstract: The shape of the femoral canal is variable, much more variable, in fact, than most contemporary designs of femoral components would suggest or can accommodate. In the face of this variability, line-to-line or surface-to-surface contact is not expected between cementless implants and much of the endosteal surface. It also is apparent that changes in implant design are still needed if the normal biomechanics of the hip joint are to be restored in each patient and if component fixation is to be optimized. Most cementless components aim to achieve proximal load transfer to the femoral canal. However, increasing clinical evidence suggests that distal filling of the femur also is necessary to minimize the incidence of postoperative symptoms, particularly in revision procedures. If this is indeed the case, more accommodating designs of femoral components are needed that will enable proximal and distal fitting at the femoral canal so that stable fixation may be achieved regardless of variations in bone geometry.

Demonstration of free radical generation in "stunned" myocardium of intact dogs with the use of the spin trap alpha-phenyl N-tert-butyl nitrone.

Abstract: Recent studies suggest that oxygen free radicals may mediate postischemic myocardial dysfunction ("stunning"), but all the evidence for this hypothesis is indirect. Thus, we used electron paramagnetic resonance (EPR) spectroscopy and the spin trap, alpha-phenyl N-tert-butyl nitrone (PBN), to directly investigate whether free radicals are produced after a 15-min coronary artery occlusion and subsequent reperfusion in 30 open-chest dogs. After intracoronary infusion of PBN, EPR signals characteristic of oxygen- and carbon-centered radical adducts were detected in the venous blood draining from the ischemic/reperfused vascular bed. The myocardial release of PBN adducts began during coronary occlusion but increased dramatically in the first few minutes after reperfusion. After this initial burst, the production of radicals abated but did not cease, persisting up to 3 h after reflow. The EPR spectra (aH beta = 2.67-2.79 G, aN = 14.75-15.00 G) were consistent with the trapping by PBN of secondary oxygen- and carbon-centered radicals, such as alkoxy and alkyl radicals, which could be formed by reactions of primary oxygen radicals with membrane lipids. There was a linear, direct relationship between the magnitude of PBN adduct production and the degree of ischemic flow reduction. Recovery of contractile function (measured as systolic wall thickening) after reperfusion was greater (P less than 0.05) in dogs given PBN than in controls. This study demonstrates that reversible regional myocardial ischemia in the intact animal is associated with prolonged free radical generation, and that the intensity of such generation is related to the severity of ischemia. The results provide direct evidence to support the hypothesis that reactive oxygen metabolites contribute to the persistent contractile dysfunction (myocardial stunning) observed after brief ischemia in vivo.

Recognition of an Endothelial Determinant for CD18-dependent Human Neutrophil Adherence and Transendothelial Migration

Abstract: Human neutrophil (PMN) attachment to human umbilical vein endothelial cells (HUVEC) was evaluated in vitro using two MAbs, R6-5-D6 and RR1/1, that recognize intercellular adhesion molecule-1 (ICAM-1), and one MAb, TS1/18, that recognizes CD18. Pretreatment of the HUVEC with anti-ICAM-1 MAbs produced greater than 50% inhibition of attachment to HUVEC, and IL-1 (0.5 U/ml)- or lipopolysaccharide (LPS) (10 ng/ml)-stimulated HUVEC, and greater than 99% inhibition of f-Met-Leu-Phe (0.5 nM) enhanced adherence. Anti-ICAM-1 MAbs also inhibited by greater than 85% the transendothelial migration induced by 4-h IL-1 (0.5 U/ml) and LPS (10 ng/ml) activation of the HUVEC. That these effects involved a CD18-dependent mechanism is supported by the following results: pretreatment of PMN with TS1/18 produced the same degree of inhibition of attachment and migration as seen with R6-5-D6. In addition, the use of both MAbs together did not further increase the inhibition of cell attachment to stimulated HUVEC. The attachment of PMN from patients with CD18 deficiency to stimulated HUVEC was not reduced by R6-5-D6, and both R6-5-D6 and TS1/18 revealed the same time course for appearance and disappearance of an adherence component on stimulated HUVEC not blocked by either MAb. These results demonstrate that attachment and transendothelial migration of PMN in vitro depend substantially on both CD18 on the PMN and ICAM-1 on the endothelial cell.

Interleukin-1 injected into mammalian brain stimulates astrogliosis and neovascularization.

Abstract: Interleukin-1 (IL-1), a protein produced by mononuclear phagocytes, helps to initiate the inflammatory response through its action upon a diverse population of cells. Recently this immunomodulator has been detected at sites of traumatized brain. As reported here, recombinant forms of IL-1 injected into the cerebral cortex of adult rats elicit not only astrogliosis but also new blood vessel growth. These responses are typical of brain injury and suggest that IL-1-secreting inflammatory cells may mediate wound healing in the CNS.

Detection of Cytomegalovirus in Urine from Newborns by Using Polymerase Chain Reaction DNA Amplification

Abstract: Polymerase chain reaction (PCR) amplification was used to detect cytomegalovirus (CMV) in tissue culture and in urine specimens from newborns. Synthetic oligonucleotide primer pairs were used to amplify DNA from the major immediate-early and the late antigen genes of CMV. Amplified products were detected by gel electrophoresis and by dot-blot hybridization with oligonucleotide probes. Using one or both of the primer pairs and associated probes, we found 46 different tissue culture isolates of CMV that were positive; no reaction products were detected when the same primers and probes were used to amplify other herpes family viruses or human genomic DNA. Urine samples from 44 congenitally infected infants were positive when tested with one or both primer pairs and probes. When compared with tissue culture, detection by gel electrophoresis provided a sensitivity of 93%, a specificity of 100%, and a predictive value of a positive result of 100%. Dot-blot analysis raised the sensitivity to 100%. We conclude that PCR amplification may be a valuable tool for diagnosing congenital CMV infection.

Point mutations in the human vitamin D receptor gene associated with hypocalcemic rickets.

Abstract: Hypocalcemic vitamin D-resistant rickets is a human genetic disease resulting from target organ resistance to the action of 1,25-dihydroxyvitamin D3. Two families with affected children homozygous for this autosomal recessive disorder were studied for abnormalities in the intracellular vitamin D receptor (VDR) and its gene. Although the receptor displays normal binding of 1,25-dihydroxyvitamin D3 hormone, VDR from affected family members has a decreased affinity for DNA. Genomic DNA isolated from these families was subjected to oligonucleotide-primed DNA amplification, and each of the nine exons encoding the receptor protein was sequenced for a genetic mutation. In each family, a different single nucleotide mutation was found in the DNA binding domain of the protein; one family near the tip of the first zinc finger (Gly----Asp) and one at the tip of the second zinc finger (Arg----Gly). The mutant residues were created in vitro by oligonucleotide directed point mutagenesis of wild-type VDR complementary DNA and this cDNA was transfected into COS-1 cells. The produced protein is biochemically indistinguishable from the receptor isolated from patients.

Purified ryanodine receptor from rabbit skeletal muscle is the calcium-release channel of sarcoplasmic reticulum.

Abstract: The ryanodine receptor of rabbit skeletal muscle sarcoplasmic reticulum was purified as a single 450,000-dalton polypeptide from CHAPS-solubilized triads using immunoaffinity chromatography. The purified receptor had a [3H]ryanodine-binding capacity (Bmax) of 490 pmol/mg and a binding affinity (Kd) of 7.0 nM. Using planar bilayer recording techniques, we show that the purified receptor forms cationic channels selective for divalent ions. Ryanodine receptor channels were identical to the Ca-release channels described in native sarcoplasmic reticulum using the same techniques. In the present work, four criteria were used to establish this identity: (a) activation of channels by micromolar Ca and millimolar ATP and inhibition by micromolar ruthenium red, (b) a main channel conductance of 110 +/- 10 pS in 54 mM trans Ca, (c) a long-term open state of lower unitary conductance induced by ryanodine concentrations as low as 20 nM, and (d) a permeability ratio PCa/PTris approximately equal to 14. In addition, we show that the purified ryanodine receptor channel displays a saturable conductance in both monovalent and divalent cation solutions (gamma max for K and Ca = 1 nS and 172 pS, respectively). In the absence of Ca, channels had a broad selectivity for monovalent cations, but in the presence of Ca, they were selectively permeable to Ca against K by a permeability ratio PCa/PK approximately equal to 6. Receptor channels displayed several equivalent conductance levels, which suggest an oligomeric pore structure. We conclude that the 450,000-dalton polypeptide ryanodine receptor is the Ca-release channel of the sarcoplasmic reticulum and is the target site of ruthenium red and ryanodine.

Interleukin-1 is an astroglial growth factor in the developing brain

Abstract: The immunomodulator interleukin-1 (IL-1) is found to be an astroglial growth factor during development of the mammalian brain. In vitro studies indicate that ameboid microglia, a class of brain mononuclear phagocytes, are the likely source of IL-1. Examination of different brain regions during development shows IL-1 production only after the appearance of ameboid microglia. These observations suggest that brain mononuclear phagocytes secrete growth factors that regulate normal growth and development of the CNS.

Uniparental disomy as a mechanism for human genetic disease.

Abstract: A female with cystic fibrosis and short stature was investigated for molecular or cytogenetic abnormalities that might explain the combined phenotype. Analysis with polymorphic DNA markers indicated that the father did not contribute alleles to the propositus for markers near the CF locus or for centromeric markers on chromosome 7. High-resolution cytogenetic analysis was normal, and the result could not be explained on the basis of nonpaternity or a submicroscopic deletion. All of the data indicate that the propositus inherited two identical copies of maternal sequences for much or all of chromosome 7. The occurrence of uniparental disomy could be explained by models postulating postfertilization error, gamete complementation, monosomic conception with subsequent chromosome gain, or trisomic conception followed by chromosome loss. Uniparental disomy in an individual with a normal chromosome analysis is a novel mechanism for the occurrence of human genetic disease.

Ankyrin and spectrin associate with voltage-dependent sodium channels in brain

Abstract: The segregation of voltage-dependent sodium channels to specialized regions of the neuron is crucial for propagation of an action potential. Studies of their lateral mobility indicate that sodium channels are freely mobile on the neuronal cell body but are immobile at the axon hillock, presynaptic terminal and at focal points along the axon. To elucidate the mechanisms that regulate sodium channel topography and mobility, we searched for specific proteins from the brain that associate with sodium channels. Here we show that sodium channels labelled with 3H-saxitoxin (STX) are precipitated in the presence of exogenous brain ankyrin by anti-ankyrin antibodies and that 125I-labelled ankyrin binds with high affinity to sodium channels reconstituted into lipid vesicles. The cytoplasmic domain of the erythrocyte anion transporter competes for the latter interaction. Neither the neuronal GABA (gamma-aminobutyric acid) receptor channel complex nor the dihydropyridine (DHP) receptor bind brain ankyrin. The results indicate that brain ankyrin links the voltage-dependent sodium channel to the underlying cytoskeleton and may help to maintain axolemmal membrane heterogeneity and control sodium channel mobility.

Polyethylene glycol precipitation for recovery of pathogenic viruses, including hepatitis A virus and human rotavirus, from oyster, water, and sediment samples.

Abstract: Polyethylene glycol 6000 precipitation was found to be an effective concentration method that enhanced the chances for detecting human virus pathogens in environmental samples. Percent recoveries from eluates of fresh and estuarine waters with 8% polyethylene glycol 6000 averaged 86 for hepatitis A virus, 77 for human rotavirus Wa, 87 for simian rotavirus SA11, and 68 for poliovirus. Percent recoveries of 97, 40, 97 and 105, respectively, for the same viruses were obtained from oyster eluates by the same procedure. Percent recoveries of 97 for hepatitis A virus and 78 for human rotavirus Wa were obtained from sediment eluates containing 2 M NaNO3 with a final concentration of 15% polyethylene glycol 6000. The polyethylene glycol method was shown to be more effective than the organic flocculation method for recovery of hepatitis A virus and rotaviruses Wa and SA11, but not of poliovirus 1 in laboratory studies. In field trials, hepatitis A virus or rotavirus or both were recovered from 12 of 18 eluates by polyethylene glycol, compared with recovery from 9 of 18 eluates by organic flocculation from fresh and estuarine waters subject to pollution.

Generation of cDNA probes directed by amino acid sequence: cloning of urate oxidase

Abstract: Urate oxidase (E.C. 1.7.3.3) catalyzes the oxidation of uric acid to allantoin in most mammals except humans and certain primates. The amino-terminal amino acid sequence for porcine urate oxidase was determined and used in a novel procedure for generating complementary DNA (cDNA) probes to this amino acid sequence. The procedure is based on the polymerase chain reaction and utilizes mixed oligonucleotide primers complementary to the reverse translation products of an amino acid sequence. This rapid and simple cDNA cloning procedure is generally applicable and requires only a partial amino acid sequence. A cDNA probe developed by this procedure was used to isolate a full-length porcine urate oxidase cDNA and to demonstrate the presence of homologous genomic sequences in humans.

DNA Diagnostics--Molecular Techniques and Automation

Abstract: Molecular biology has revolutionized the understanding of many aspects of human disease. Ongoing developments in DNA diagnostics--the analysis of disease at the nucleic acid level--will soon provide automated, rapid, and inexpensive analyses for DNA or RNA sequences associated with genetic, malignant, and infectious diseases. DNA diagnostics will also facilitate the identification of disease-associated genes at birth, thus creating new opportunities for preventive medicine.

Sugar and signal-transducer binding sites of the Escherichia coli galactose chemoreceptor protein.

Abstract: D-galactose-binding (or chemoreceptor) protein of Escherichia coli serves as an initial component for both chemotaxis towards galactose and glucose and high-affinity active transport of the two sugars. Well-refined x-ray structures of the liganded forms of the wild-type and a mutant protein isolated from a strain defective in chemotaxis but fully competent in transport have provided a molecular view of the sugar-binding site and of a site for interacting with the Trg transmembrane signal transducer. The geometry of the sugar-binding site, located in the cleft between the two lobes of the bilobate protein, is novel in that it is designed for tight binding and sequestering of either the alpha or beta anomer of the D-stereoisomer of the 4-epimers galactose and glucose. Binding specificity and affinity are conferred primarily by polar planar side-chain residues that form intricate networks of cooperative and bidentate hydrogen bonds with the sugar substrates, and secondarily by aromatic residues that sandwich the pyranose ring. Each of the pairs of anomeric hydroxyls and epimeric hydroxyls is recognized by a distinct Asp residue. The site for interaction with the transducer is about 18 A from the sugar-binding site. Mutation of Gly74 to Asp at this site, concomitant with considerable changes in the local ordered water structures, contributes to the lack of productive interaction with the transmembrane signal transducer.

Simple dislocation of the elbow in the adult. Results after closed treatment.

Abstract: The long-term results after treatment of simple dislocation of the elbow in fifty-two adults were evaluated with regard to limitation of motion, pain, instability, and residual neurovascular deficit. All patients were treated with traditional closed reduction, but the duration of immobilization before commencement of active motion varied. Goniometric, photographic, and radiographic data were compiled for these patients, who had an average follow-up of 34.4 months. Despite the generally favorable prognosis for this injury, 60 per cent of the patients reported some symptoms on follow-up. A flexion contracture of more than 30 degrees was documented in 15 per cent of the patients; residual pain, in 45 per cent; and pain on valgus stress, in 35 per cent. Prolonged immobilization after injury was strongly associated with an unsatisfactory result. The longer the immobilization had been, the larger the flexion contracture (p less than 0.001) and the more severe the symptoms of pain were. The results indicate that early active motion is the key factor in rehabilitation of the elbow after a dislocation.

Colony-stimulating factors as promoters of ameboid microglia

Abstract: Immunomodulators were tested for their ability to stimulate proliferation and biologic activity of ameboid microglia. Only the colony-stimulating factors (CSFs), multipotential-CSF (multi-CSF) and granulocyte/macrophage-CSF (GM-CSF), were potent mitogens for microglia. Other immunomodulators, including interleukin-1, interleukin- 2, interferon gamma, tumor necrosis factor, or granulocyte-CSF (G-CSF), had no effect upon microglial growth in vitro. Multi-CSF or GM-CSF were also observed to induce more rapid phagocytosis of polystyrene microspheres by cultured ameboid cells. In order to determine which immunomodulators alter brain inflammatory responses in vivo, we infused recombinant forms of GM-CSF, multi-CSF, macrophage-CSF, or G-CSF into the cerebral cortex of rats. Within 48 hr after infusion multi-CSF or GM-CSF stimulated the appearance of large numbers of mononuclear phagocytes at the site of injection. These same factors also accelerated the clearance of polystyrene microspheres from the brain. Our observations indicate that certain classes of immunomodulators which are mitogens and activators of ameboid microglia in vitro amplify the inflammatory response of the CNS in vivo by action upon intrinsic brain mononuclear phagocytes.

Indomethacin in the treatment of premature labor. Effects on the fetal ductus arteriosus.

Abstract: Indomethacin is a potent agent in the treatment of premature labor, but its use has been limited because of concern about its constrictive effects on the fetal ductus arteriosus. To study these effects we used serial fetal echocardiography in 13 pregnant women in premature labor who received indomethacin according to three different dose schedules, ranging from 100 to 175 mg per day, for a maximum of 72 hours. The gestational ages of the fetuses ranged from 26.5 to 31.0 weeks. The detection of ductal constriction in 7 of the 14 fetuses by echocardiography led to the discontinuation of indomethacin. Three fetuses also had tricuspid regurgitation. There was no statistically significant difference between the mean (±SEM) gestational age of the fetuses with ductal constriction and that of those without constriction (29.3±0.59 and 28.4±0.52, respectively). There was no relation between serum indomethacin levels in the mothers and ductal constriction. In all seven fetuses affected, ductal constriction ...

Noradrenergic enhancement of long-term potentiation at mossy fiber synapses in the hippocampus

Abstract: 1. We tested several hypotheses related to the modulation of long-term potentiation (LTP) by norepinephrine (NE) at the mossy fiber synapses in the rat hippocampal slice preparation using extracell...

N-acetylneuraminyllactose-binding fibrillar hemagglutinin of Campylobacter pylori: a putative colonization factor antigen.

Abstract: Campylobacter pylori is the causative agent of gastritis and possibly of peptic and duodenal ulcers in adults. Histological observations show C. pylori attached to gastric epithelium as well as in the mucus layer of the stomach. We found that clinical isolates of C. pylori possess a cell-bound hemagglutinin detectable with human erythrocytes (all phenotypes tested) and those of a variety of animal species. The C. pylori hemagglutinin is antigenic, heat sensitive, and destroyed by pronase and papain but resistant to pepsin and trypsin. The hemagglutinin has fibrillar morphology; C. pylori-erythrocyte interaction displays very intimate contact, which is typical of fibrillae-mediated attachment. Fibrillae were removed from C. pylori by solubilization with N-octylglucose. After partial purification and removal of N-octylglucose by dialysis, the protein reaggregated, with the assembly of fibrillar structures. Hemagglutination inhibition was observed with the sialoproteins fetuin, alpha 2-macroglobulin, and glycophorin A but not with asialofetuin or asialoglycophorin A. The erythrocyte receptor was more sensitive to destruction by a neuraminidase specific for the N-acetylneuraminyl-alpha(2-3)-galactopyranosyl [NeuAc(2-3)Gal] sequence than one specific for NeuAc(2-6)Gal. Hemagglutination-inhibition assays with N-acetylneuraminyl-alpha(2-3)-lactose [NeuAc(2-3)-lactose] and NeuAc(2-6)-lactose confirmed that the C. pylori hemagglutinin preferentially binds to the NeuAc(2-3)Gal isomer of NeuAc-lactose. Based upon the above-described properties of the C. pylori fibrillar hemagglutinin, we conclude that this antigen should be designated as a putative colonization factor antigen.

The clinical outcome of prospective screening for multiple endocrine neoplasia type 2a. An 18-year experience

Abstract: An important question facing physicians who care for families with multiple endocrine neoplasia type 2a is whether prospective screening to detect early abnormalities of the thyroid, parathyroid, or adrenal glands favorably influences the ultimate course of the disease. An 18-year study of a large family has allowed us to examine the effect of early treatment on the clinical course of the disease. Of 22 patients who underwent thyroidectomy for early C-cell abnormalities, 19 remained free of detectable medullary thyroid carcinoma according to all criteria, at a mean of 11 years after thyroidectomy. None of the 22 patients had evidence of parathyroid disease either at the time of surgery or after a mean follow-up of 10 years. Prospective screening for adrenal medullary abnormalities by means of measurement of 24-hour urinary epinephrine excretion and the ratio of urinary epinephrine to norepinephrine was predictive of pheochromocytoma in 10 of 11 patients (with a false negative result in one patient) but was not useful in diagnosing adrenal medullary hyperplasia. We conclude that regular, prospective screening and early treatment of the manifestations of multiple endocrine neoplasia can prevent metastasis of medullary thyroid carcinoma and the morbidity and mortality caused by pheochromocytoma.

Sequential activation of alpha-actin genes during avian cardiogenesis: vascular smooth muscle alpha-actin gene transcripts mark the onset of cardiomyocyte differentiation.

Abstract: The expression of cytoplasmic beta-actin and cardiac, skeletal, and smooth muscle alpha-actins during early avian cardiogenesis was analyzed by in situ hybridization with mRNA-specific single-stranded DNA probes. The cytoplasmic beta-actin gene was ubiquitously expressed in the early chicken embryo. In contrast, the alpha-actin genes were sequentially activated in avian cardiac tissue during the early stages of heart tube formation. The accumulation of large quantities of smooth muscle alpha-actin transcripts in epimyocardial cells preceded the expression of the sarcomeric alpha-actin genes. The accumulation of skeletal alpha-actin mRNAs in the developing heart lagged behind that of cardiac alpha-actin by several embryonic stages. At Hamburger-Hamilton stage 12, the smooth muscle alpha-actin gene was selectively down-regulated in the heart such that only the conus, which subsequently participates in the formation of the vascular trunks, continued to express this gene. This modulation in smooth muscle alpha-actin gene expression correlated with the beginning of coexpression of sarcomeric alpha-actin transcripts in the epimyocardium and the onset of circulation in the embryo. The specific expression of the vascular smooth muscle alpha-actin gene marks the onset of differentiation of cardiac cells and represents the first demonstration of coexpression of both smooth muscle and striated alpha-actin genes within myogenic cells.

The G protein-gated atrial K + channel is stimulated by three distinct G I α-subunits

Abstract: The gunanine nucleotide-binding protein, Gi, which inhibits adenylyl cyclase, has recently been shown to have three subtypes of the a-subunit, termed Giα-1, Giα-2 and Giα-3. They share 87–94% amino-acid sequence homology1–10 and so are difficult to separate from one another. Among other functions11,12–14, purified preparations activate K+ channels15–21 but there is confusion over which of the subtypes activates the muscarinic K+ channels of the atrial muscle of the heart: Giα-3, also termed Gk15, has been shown to activate this channel but it is not clear whether Giα-l22 does21 or does not23,24. To clarify this problem, we expressed the subtypes separately in Escherichia coli to eliminate contamination by other subtypes and tested the recombinant α- chains on atrial muscarinic K+ channels. Although we anticipated that only Giα-3 would have Gkactivity, to our surprise all three recombinant subtypes were active, from which we deduce that the Gi subtypes are multifunctional.

Direct G protein gating of ion channels.

Abstract: Guanine nucleotide binding (G) proteins couple a variety of receptors to ionic channels. Until recently the pathway was thought to be indirect via cytoplasmic second messengers; now the heterotrimeric G proteins are known to act directly on K+ and Ca2+ channels. Here we summarize recent developments concerning this widespread mechanism which we call G protein gating of ion channels. A specific pertussis toxin-sensitive G protein called Gk, purified from human red blood cells, activates a unique K+ channel and Gk, or a similar G protein, couples this channel to muscarinic atrial receptors. The alpha-subunit (alpha k) at less than 10 pM mediates the effects, and alpha k also activates K+ channels directly in neurosecretory cells. The G protein stimulatory to adenylyl cyclase, Gs, gates directly through its alpha-subunit, specific Ca2+ channels in heart and skeletal muscle T tubules. Hence, one G protein can have two distinct effectors.

Perforator-based flaps for low posterior midline defects.

Abstract: A new type of flap is described based on unnamed perforators located near the midline of the lower back region. Such flaps combine the superior blood supply of the myocutaneous flap with the lack of donor-site morbidity of a skin flap. Five clinical cases are presented, showing how such perforators can augment skin flaps or create custom-designed island flaps. The dissection of the flap is described, and further possibilities for its use are suggested.

Immunization of Pregnant Women with a Polysaccharide Vaccine of Group B Streptococcus

Abstract: Immunization of pregnant women with a polysaccharide vaccine of group B streptococcus is a promising strategy for the prevention of perinatal infections caused by group B streptococci. To explore the feasibility of this strategy, we vaccinated 40 pregnant women at a mean gestation of 31 weeks with a single 50-microgram dose of the Type III capsular polysaccharide of group B streptococcus. The only adverse effect detected was a mild local reaction in nine women (22 percent). Of the 35 women with low or unprotective antibody levels before immunization (less than 2 micrograms per milliliter), 20 (57 percent) responded to the vaccine. The geometric mean antibody level rose from 1.3 to 7.1 micrograms per milliliter four weeks after vaccination (P less than 0.02), and these levels persisted at delivery and three months post partum. Sixty-two percent of the vaccine-induced immunoglobulin in the mothers was IgG, which readily crosses the placenta. Infant antibody levels in cord serum correlated directly with maternal antibody levels at delivery (r = 0.913, P less than 0.001). Of the 25 infants born to women who responded to the vaccine, 80 percent continued to have protective levels of antibody at one month of age and 64 percent had protective levels at three months. Serum samples from infants with greater than or equal to 2 micrograms of antibody to Type III group B streptococcus per milliliter uniformly promoted efficient opsonization, phagocytosis, and bacterial killing in vitro of Type III strains. This effect could be mediated exclusively by the alternative complement pathway. Although this vaccine with an overall response rate of 63 percent is not optimally immunogenic, we conclude that maternal immunization is feasible and can provide passive immunity against systemic infection with Type III group B streptococcus in the majority of newborns. Larger trials with better vaccines will be required to evaluate the safety and clinical effectiveness of this strategy.

Insulin-like growth factor (IGF) binding protein complementary deoxyribonucleic acid from human HEP G2 hepatoma cells: predicted protein sequence suggests an IGF binding domain different from those of the IGF-I and IGF-II receptors.

Abstract: The primary structure of an insulin-like growth factor (IGF) binding protein produced by human HEP G2 hepatoma cells has been deduced from the cDNA sequence. The 234 amino acid protein has a predicted molecular mass of 25,274 and contains a single, distinctive cysteine-rich region. The N-terminal sequence of this protein is quite similar to the limited sequence data available for a rat IGF binding protein produced by BRL-3A cells and suggests a common ancestral origin. In contrast, the HEP G2 IGF binding protein sequence bears no similarity to the N-terminal 15 amino acids of a 53 kilodalton binding protein purified from human plasma. Comparison of full-length protein sequences for the IGFI and IGF-II receptors with that of the HEP G2 IGF binding protein also fails to demonstrate any significant similarities among these three proteins, and suggests that each contains a unique binding domain for the IGF peptides.