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PubMedDate not supplied

Strength of the pulmonary blood-gas barrier.

The mammalian pulmonary blood-gas barrier is well known to be extremely thin. For example, in the human lung, half of the area of the barrier (the 'bulging' part) has a thickness of only 0.2-0.4 micron. We show here that the barrier is also immensely strong. This is an essential requirement because the capillary wall stresses during heavy exercise become very large (about 7 x 10(4) N/m2 = 70 kPa) when capillary pressure increases to 30 mmHg. Stress failure of the pulmonary capillary wall consistently occurs in experimental rabbit preparations at abnormally high pressures exceeding 40 mmHg and may be the cause of bleeding into the lung in galloping racehorses. The great strength of the thin side of the blood-gas barrier can be attributed to the extracellular matrix, especially the type IV collagen which is predominantly located in the very thin lamina densa. The alveolar wall is therefore particularly vulnerable to injurious agents which attack type IV collagen such as autoantibodies in Goodpasture's Syndrome and perhaps neutrophil elastase in emphysema. The combination of extreme thinness and great strength of the blood-gas barrier poses a unique design requirement.

Animals↗
PubMed1990

Beta-endorphin alters the course of central nervous system disease induced by a temperature-sensitive vesicular stomatitis virus in reconstituted nude mice.

A 100 plaque forming unit (pfu) dose of a temperature-sensitive (ts) mutant of vesicular stomatitis virus (VSV), tsG31 KS5, engendered a slowly progressive paralytic central nervous system (CNS) disease that killed all BALB/c nude mice within 28 days. Reconstitution of nude mice with 10(7) syngeneic splenocytes 24 h before intracerebral inoculation with tsG31 KS5 VSV, however, protected 92% of the animals from death. When these reconstituted animals were injected intracerebroventricularly with 14 pmol of beta-endorphin 24 h after reconstitution with splenocytes and 24 h before inoculation with tsG31 KS5 VSV, only 72% of the animals survived. Furthermore, whereas 40% of the afflicted reconstituted nude mice given intracerebroventricular injections of sterile water were able to recover from the symptoms of disease, those surviving animals which received beta-endorphin were unable to do so. A single intravenous injection of 14 pmol beta-endorphin, or repeated postinfection administration of 28 pmol of beta-endorphin intravenously into nude mice reconstituted with syngeneic splenocytes, which were pretreated with beta-endorphin, did not alter the course of CNS disease induced by tsG31 KS5 VSV. The effect induced by intracerebroventricular injection of beta-endorphin was antagonized by naloxone, but not by the neuropeptide fragment beta-endorphin-(1-27). A simultaneous intracerebroventricular injection of reconstituted nude mice with 1220 pmol of naloxone and 14 pmol of beta-endorphin resulted in a 89% survival rate, and 33% of the afflicted animals were able to overcome the symptoms of the disease induced by tsG31 KS5 VSV. Intracerebroventricular injection of reconstituted nude mice with 330 pmol of beta-endorphin-(1-27) and 14 pmol of beta-endorphin resulted in a 72% survival rate and the surviving animals were unable to improve appreciably the clinical status of their disease. Injection of reconstituted nude mice with either 1220 pmol of naloxone or 330 pmol of beta-endorphin-(1-27) alone did not alter the course of the CNS disease in any way. A single intracerebroventricular injection of 29 pmol of another psychoactive peptide, [Des-Tyr]-endorphin, 24 h after reconstitution of nude mice with splenocytes and 24 h prior to infection with virus, resulted in 74% survival; and 39% of the afflicted animals were able to recover from the clinical symptoms.

Animals↗
PubMed1991

An immune cell population that responds to beta-endorphin and is responsible for protecting nude mice from the fatal consequences of a virus infection of the central nervous system.

Reconstitution of 3- to 4-week-old BALB/c nude (nu/nu) mice with 10(7) syngeneic splenocytes, 48 h before intracerebral inoculation with a temperature-sensitive (ts) mutant of VSV (tsG31 KS5), provided protection from the fatal consequences of clinical disease in 80-90% of the infected animals. Reconstitution of animals with 10(7) splenocytes, first depleted of natural killer (NK) cells with anti-asialo GM1 and complement, also afforded protection against the infectious disease. Depletion of T-lymphocytes with anti-thy-1.2 antibody and complement, however, provided little protection with approximately 40% of the animals succumbing to the virus infection within 30 days post-infection. A single intracerebroventricular injection with 14 pM of beta-endorphin, 24 h prior to viral infection, led to an increased fatality of mice previously reconstituted with T-lymphocytes but not in animals receiving only syngeneic NK cells. The increased fatality caused by the neuropeptide was antagonized by naloxone but not beta-endorphin-(1-27). Separation of splenocyte cell populations by buoyant density centrifugation demonstrated that small race lymphocytes, and not the large granular lymphocytes, were responsible for protection of nude mice from the central nervous system infection with ts-VSV. The beta-endorphin-responsive immune cells were shown to be a minor fraction of the small race T-lymphocyte population that bear the asialo-GM1 marker.

Animals↗
PubMed1992

Spontaneous bursting and non-bursting activity in morphologically identified neurons of the rat dorsolateral septal nucleus, in vitro.

Membrane potential-dependent changes in the repetitive firing properties of morphologically identified rat dorsolateral septal nucleus neurons were investigated in a submerged slice preparation using intracellular recording techniques and lithium acetate-Lucifer Yellow-filled microelectrodes. The results indicate that the majority of dorsolateral septal nucleus neurons are capable of burst firing and suggest, moreover, the existence of neuronal subtypes with distinct differences in spike waveform and the pattern of spontaneous activity. In the largest proportion of neurons, single spike activity predominated at membrane potentials near rest while burst-like discharges prevailed at more hyperpolarized membrane potentials. Less frequently observed were neurons exhibiting different burst waveforms at various membrane potentials. In a few neurons, hyperpolarization slowed neuronal firing but did not elicit burst-like discharges. Characteristics such as the presence of burst or single spike discharges, spike afterpotentials, and the membrane potential dependence of repetitive firing patterns did not appear to be closely associated with membrane time constant, membrane resistance, or resting membrane potential. A detailed examination of the somatodendritic and axonal morphology of the Lucifer Yellow-filled cells revealed that these electrophysiologically identified neurons in the dorsolateral septal nucleus are morphologically heterogeneous. However, there did not appear to be any correlation between a particular somatodendritic morphology and the expression of a distinct spontaneous firing pattern. The present findings demonstrate that neurons in the rat dorsolateral septal nucleus are morphologically diverse and capable of intrinsically generating rhythmic neuronal activity. Similar patterns of rhythmic neuronal firing in vivo may provide a substrate for the integration of afferent neuronal activity and have a central role in intraseptal circuitry necessary for generation of hippocampal theta rhythm.

Acetates↗
PubMed1991

The mechanical control system of bone in weightless spaceflight and in aging.

Bone loss is notable in elderly persons and in astronauts returning from spaceflight, however, the bone changes in these radically different patient populations appear morphologically similar. Bone structure depends upon several independent basic processes: growth, modeling, and remodeling. Each process follows a stereotyped sequence of steps. Alteration of any step may yield a similar bone loss, although from an entirely different mechanism. Mechanical forces appear to coordinate the fundamental bone shaping processes by a negative feedback control system. Determining how mechanical signals control the mass, architecture, and strength of bone may establish the limits by which exercise can prevent osteoporosis in the elderly and in astronauts despite obvious differences in etiology.

Adult↗
PubMed1989

Left subclavian flap aortoplasty for coarctation of the aorta: effects on forearm vascular function and growth.

This study evaluated vascular function and growth of the forearm in nine children (mean age 9.2 years) who had undergone left subclavian flap aortoplasty for the infantile type of coarctation of the aorta many years (mean 9.0) earlier. Variables used to investigate bilateral forearm vascular function included forearm blood flow and resistance measured by strain gauge plethysmography under rest conditions, in response to 30 s of static handgrip exercise at 40% maximal voluntary contraction and in response to 10 min of forearm arterial occlusion (that is, the reactive hyperemic blood flow response). Forearm growth was ascertained by measuring right and left forearm volumes, lengths, circumferences and skinfold thickness. Mean arterial pressure at rest in the right and left arms differed by 9% (right 78.2 +/- 2.1, left 71.0 +/- 2.7 mm Hg; p less than 0.05). Forearm blood flow, however, was not significantly different between the surgically altered left arm and the normal right arm under any of the study conditions. Likewise, forearm vascular resistance was not statistically different under any conditions, although the left arm tended to have a lower resistance at rest (right 23.5 +/- 3.2, left 18.7 +/- 2.0 mm Hg.min.100 ml/ml; p = 0.057). Left forearm anthropometric measurements showed a 9% reduction in volume and a 3% reduction in circumference and length. In addition, skinfold thickness tended to be larger on the left arm, suggesting that this limb had a smaller muscle mass. In conclusion, early repair with a subclavian flap does not impair vascular function in the altered limb and is associated with only minor reductions in forearm growth variables. Hence, left subclavian flap aortoplasty appears to be a safe and effective procedure for repair of coarctation of the aorta.

Aortic Coarctation↗
PubMed1990

Associative learning changes intrinsic to Hermissenda type A photoreceptors.

The eyes of the nudibranch mollusc Hermissenda have previously been shown to contain 2 classes of photoreceptors. Type B photoreceptors exhibit increased light responses and membrane excitability after repeated pairings of light and rotation and play an important role in the mediation of associatively produced reductions in phototactic behavior. Type A photoreceptors have also been shown to change with associative training. In previous research, Type A photoreceptors from trained animals were found to have reduced light responses. Because these recordings were obtained from synaptically intact cells, it was not possible to determine whether the effects of associative training reflected changes in synaptic input to Type A photoreceptors or intrinsic changes in somatic conductances. In the present study, intracellular recordings from synaptically isolated Type A photoreceptors were obtained on retention days after training, and pairing-specific decreases in light-induced generator potentials and decreases in resting input resistance were observed. Current- and voltage-clamp analysis of Type A photoreceptors from untrained animals revealed that an important determinant of the steady-state light response was a calcium-activated K+ current (IK-Ca). Thus, Type A photoreceptors also appear to be a primary site for associative information storage in Hermissenda. It is suggested that enhancement of IK-Ca by associative training may contribute to the diminished light response of Type A photoreceptors.

Accommodation, Ocular↗
PubMed1991

Modulation of transmembrane signalling in HL-60 granulocytes by tumour necrosis factor-alpha.

Differentiated HL-60 granulocytes were used to study the mechanism by which tumour necrosis factor-alpha (TNF) enhances responses to N-formyl-methionyl-leucylphenylalanine (FMLP). Cultivation of differentiated HL-60 cells with 100 units of TNF/ml for 24 h resulted in a 3-fold increase in superoxide release and 4-fold increase in prostaglandin E2 production on stimulation with 1 microM-FMLP. On the other hand, cultivation with TNF failed to increase phorbol diester stimulation of superoxide release. Formyl-peptide-receptor expression determined on isolated membranes from cells cultivated with TNF (TNF-M) was increased by 50% compared with membranes from control cells (NM). Similarly, FMLP binding to intact HL-60 cells was increased by cultivation with TNF. Guanine-nucleotide-binding proteins (G-protein) levels were not different between TNF-M and NM, as determined by pertussis-toxin-catalysed ADP-ribosylation and by immunoblotting with antisera recognizing alpha i2 subunit. Binding of guanosine 5'-[gamma-thio]triphosphate and GTP hydrolysis stimulated by FMLP were enhanced by about 50% in TNF-M. The efficiency of G-protein activation by formyl-peptide receptors did not differ between TNF-M and NM. TNF regulates expression of formyl-peptide receptors independently of G-protein levels. The regulation of receptor expression is one mechanism by which TNF enhances cell responses to formylated peptides.

Adenosine Diphosphate Ribose↗
PubMed1992

High altitude pulmonary edema is caused by stress failure of pulmonary capillaries.

The pathogenesis of high altitude pulmonary edema (HAPE) is disputed. We propose that the mechanism is stress failure of pulmonary capillaries. The main features to be accounted for are the strong association with pulmonary hypertension, the high permeability characteristics of the edema, and the presence of inflammatory markers in the lung lavage fluid. When the capillary pressure is raised to about 40 mmHg in anesthetized rabbits, ultrastructural damage to the capillary walls is seen including breaks in the capillary endothelial layer, alveolar epithelial layer, and sometimes all layers of the wall. This results in a high permeability form of edema with the escape of high molecular weight proteins and blood cells into the alveolar spaces. In addition the basement membrane of the endothelial layer is frequently exposed, and we suggest that this highly reactive surface attracts and activates platelets and neutrophils. The result is the formation of small thrombi which are frequently seen in HAPE, and the presence of inflammatory markers such as leukotriene B4 and the complement fragment C5a in the lung lavage fluid. Hypoxic pulmonary vasoconstriction raises the pressure in some capillaries because the constriction is uneven. Since HAPE has its origin in the high pulmonary artery pressure, the objective of treatment should be to reduce the pressure by descent, administering oxygen, or giving drugs such as calcium channel blockers (e.g. nifedipine) which relax pulmonary vasoconstriction. Stress failure of pulmonary capillaries satisfactorily accounts for the features of HAPE.

Altitude Sickness↗
PubMed1991

Maternal inheritance of centrosomes in mammals? Studies on parthenogenesis and polyspermy in mice.

The centrosome, the microtubule-organizing center of the cell, is introduced typically by the sperm at fertilization. In some mammals, however, this paternal pattern of inheritance appears to be violated. The hypothesis that the centrosome is maternally inherited was tested during parthenogenesis, polyspermy, and polygyny as well as after recovery from microtubule inhibition at first mitosis. During parthenogenesis the paternal contribution was absent, and in polyspermy the paternal contribution was multiplied. Haploid and diploid parthenogenotes as well as polyspermic and digynic fertilized eggs each segregated their centrosomes to organize a bipolar mitotic apparatus. Oocytes recovering from a nocodazole block formed two normal bipolar mitotic apparatus; the paternal chromosomes aligned at one spindle equator, while the maternal chromosomes were found at the other. These results show that the centrosome is maternally inherited from cytoplasmic sites in the mouse. The evolutionary switch from paternal to maternal inheritance in mammals might be related to the additional dangers that parthenogenesis represents: a threat to the life of the mother as well as to the life of the fetus.

Animals↗
PubMedDate not supplied

A simple procedure for cross-linking complementary oligonucleotides.

A simple, efficient procedure for cross-linking two complementary oligonucleotides, which does not require chemical modification of either oligonucleotide, is described. One of the oligonucleotides is first converted to the 5'-phosphorothioate derivative with polynucleotide kinase. It is then incubated with its complement in the presence of 1 microM trans-platinum(II)diammine dichloride. After overnight incubation, 40-50% cross-linking is observed. DNA synthesis by the Klenow fragment of Escherichia coli DNA polymerase I is blocked at the cross-linked site, resulting in the formation of truncated products. Potassium platinous chloride (K2PtCl4) and cis-platinum(II)diammine dichloride form cross-links less efficiently than the trans isomer.

Base Sequence↗
PubMed1991

Time-constant adaptations in heart failure.

The circulatory compensatory mechanisms designed to cope quickly with physiological stress (e.g. sympathetic nervous system and the Frank-Starling mechanism) are less effective when there is chronic pathological stress, such as congestive heart failure (CHF). Other mechanisms come into play that operate over a longer time (e.g. activation of the renin-angiotensin-aldosterone system, myocardial hypertrophy and physiological deconditioning). Changes in blood vessels and skeletal muscle metabolism that result from inadequate delivery of oxygenated blood to working muscles belong to the group of mechanisms that develop slowly. When CHF therapy is successful, the abnormalities produced by this latter group of mechanisms will improve, but slowly. The concept that compensatory mechanisms have either short or long time constants for activation and reversal may explain why exercise tolerance improves much later than haemodynamics, which can be reversed acutely with vasodilator therapy.

Adaptation, Physiological↗
PubMed1992

Zfp-37, a new murine zinc finger encoding gene, is expressed in a developmentally regulated pattern in the male germ line.

To begin to examine the function in the mouse testis of genes containing the zinc finger motif, we have screened an adult mouse total testis cDNA library with probes to a conserved region of zinc fingers. We have isolated cDNAs for a new murine zinc finger encoding gene that has been designated Zfp-37. Northern blot hybridization analysis revealed Zfp-37 transcripts at high levels in the testis, the only adult tissue in which Zfp-37 expression was observed. Zfp-37 was also expressed at lower levels in the mid-gestation embryo and placenta. The major testicular transcripts are 2.3 and 2.6 kb. A 4.0 kb transcript was detected at lower levels in the testis as well as in embryo and placenta. Northern blot and in situ hybridization analysis revealed that expression of Zfp-37 was most abundant in germ cells which have completed meiosis and are undergoing the complex morphogenetic changes of spermiogenesis. The pattern of expression of Zfp-37 and the presence of the zinc finger domain suggest that Zfp-37 may have a role in regulating spermiogenesis.

Amino Acid Sequence↗
PubMed1992

Effects of magnitude and duration of compression on spinal nerve root conduction.

Spinal nerve root compression occurs commonly in conditions such as herniated nucleus pulposus, spinal stenosis, and trauma. However, the pathophysiology of the symptoms and signs related to spinal nerve root compression is poorly understood. The purpose of the present study was to assess and compare effects of various pressures and durations of acute compression on spinal nerve root conduction in the pig cauda equina. Efferent conduction (compound motor action potentials) and afferent conduction (compound nerve action potentials) were monitored during compression for 2 or 4 hours with compression pressures of 0 (sham), 50, 100, or 200 mm Hg. Recovery from compression was monitored for 1.5 hours. No significant deficits in spinal nerve root conduction were observed with 0 or 50 mm Hg compression, compared to significant conduction deficits induced by 100 and 200 mm Hg compression. Three-way analysis of variance demonstrated significant effects of compression pressure and duration on conduction at the end of compression and recovery, with a significant difference between efferent and afferent conduction at the end of the recovery period. These observations suggest an interaction between biomechanical and microvascular mechanisms in the production of nerve root conduction deficits. Such information may relate to the motor and sensory dysfunction in clinical conditions associated with spinal nerve root compression.

Action Potentials↗
PubMed1990

The nucleocapsid protein of vesicular stomatitis virus isolated from the brains of nude mice is responsible for abated viral RNA synthesis at the normal body temperature of mice.

Six temperature-sensitive mutants of vesicular stomatitis virus (VSV) were isolated from the central nervous system (CNS) of athymic nude mice. The nude mice had been reconstituted with syngeneic T lymphocytes and then infected with a temperature-sensitive mutant of VSV, tsG31-KS5 VSV, for 20 days. In BHK-21 cells incubated at 38 degrees C, the normal body temperature of mice, all six CNS virus clones had diminished RNA synthesis, when compared to RNA production in BHK-21 cells incubated at 31 degrees C. In contrast, the original tsG31-KS5 VSV mutant synthesized more RNA at 38 degrees C than it did at 31 degrees C. In vitro transcription assays were exploited to discern which viral protein(s) was functionally accountable for the abated synthesis of RNA of the CNS VSV isolates. The ribonucleoprotein complexes from the CNS VSV isolates were disrupted and template (N protein and RNA) and enzyme (L and NS proteins) fractions were purified. In vitro transcription assays were performed with template fractions of the brain isolates, added to enzyme fractions either wild-type wt VSV or tsG31-KS5 VSV, or with template fractions of wt VSV or tsG31-KS5 VSV mixed with enzyme fractions of the CNS isolates. The template fraction was responsible for the decrease in RNA synthesis in all six of the brain-isolated clones. When the template fractions of wt or tsG31-KS5 VSV were mixed with enzyme fractions of all the CNS-derived VSV, except BP5A VSV, leader sequence RNA and large Mr transcripts were transcribed. One clone, BP5A VSV, did not synthesize RNA when mixed with either template or enzyme of wt VSV, and probably had more than one functional mutation that influenced viral RNA synthesis.

Animals↗