Hypothalamic knife-cut hyperphagia and obesity in weanling rats

In previous reports weanling female rats fed a high-fat diet had a delayed response to hypothalamic knife cuts. In the present report similar cuts in similar rats fed a standard low fat diet became overweight without delay, suggesting that dietary fat is a critical variable in juvenile onset obesity. Adult rats given knife-cuts comparable to those in the weanlings gained weight far more rapidly and achieved higher weights than did those cut as weanlings, suggesting that appetite modulating axons can develop after weaning. Finally, group vs single housing did not influence the age of onset or the magnitude of knife-cut obesity.     

Sleep related breathing disorders in older men: A search for underlying mechanisms

—The incidence of sleep-related breathing disorders (SRBDs) associated with hemoglobin desaturation was determined by nocturnal polygraphic evaluations in 26 healthy men, aged 55–70 years. Sixteen subjects (62%) had abnormal rates of at least 12 episodes per hour of sleep: 8 had occlusive, and 8 had central apnea or hypopnea. During waking ten of 16 SRBD subjects and only one subject without SRBDs exhibited either an elevated nasopharyngeal airway resistance (n=4) or a reduced ventilatory response to hypercapnia (n=4) and/or hypoxia (n=3). However, these abnormalities were not related to the type or severity of SRBDs, and 6 subjects with SRBDs demonstrated no respiratory defect. We conclude that SRBDs have a very high incidence in older males and are not usually secondary to pulmonary cardiac, neurological, or behavioral disorders. Additionally, we hypothesize that abnormalities in ventilatory control or upper airway resistance contribute to SRBDs, but depression of brain stem reticular formation activity during sleep plays a primary role in these disorders. Factors related to both aging and SRBDs are reviewed. These include reduced chemoreceptor responses, altered steroid hormone metabolism, and use and metabolism of hypnotic drugs and alcohol.     

Ultrastructural study of microsporidian invasion into cells

Summary Nosema michaelis spores were primed to discharge extracellularly or into culture medium 199 containing ascites leukemia EL4 cells, mouse macrophages, neuroblastoma C1300 adapted to ascites, human red blood cells, and blue crab epithelial cells and hemocytes.Before discharge, the polar tube has a single membrane enveloping a glycoprotein-like matrix. After extrusion, there are two membrane envelopes surrounded by a glycoprotein sheath. This sheath is silver methenamine negative, trypsinsensitive, has low solubility to 1% SDS treatment, and binds ferritin-conjugated concanavalin A.Before spore discharge, the sporoplasm is dispersed, uncompartmentalized by any membrane and exterior to the extrusion apparatus. After passage through the extrusion tube, the sporoplasm ends up in vesicle formed at the end of extruded tube. The sporoplasm nucleus maintains its integrity during extrusion; both the cytoplasm and nuclear components of the discharged sporoplasm are compartmentalized within membranes. After 15–20 min within the host cytoplasm, the sporoplasm shows obvious cytoplasmic reorganization and endoplasmic reticulum synthesis.Within the host cell, the sporoplasm is surrounded by two envelopes, the outer of which appears continuous with the polar tube sheath. Two envelopes surround the parasite when it is injected into extracellular medium, into human red blood cells, or into ascites leukemia EL4 cells. One envelope is lost when the sporoplasm is injected into normal host cells such as blue crab hemocytes and epithelial cells.A fibrous corona surrounds the sporoplasm in ascites leukemia EL4 cells, neuroblastoma C1300 or mouse macrophages. This corona is believed to be host reaction material since it is absent when parasites are injected into blue crab gut epithelial cells and hemocytes, into extracellular medium, or into human red blood cells.Supported by training grant from the National Institutes of Health A 10092. Special thanks are extended to Prof. William Trager.     

Ontogenetic transition in fetal wound transforming growth factor-beta regulation correlates with collagen organization

Fetal rat skin transitions from scarless fetal-type repair to adult-type repair with scar between day 16 (E16) and day 18 (E18) of gestation (term = 21.5 days). Deficient transforming growth factor (TGF)-beta 1 and -beta 2 injury response has been proposed as a mechanism for scarless fetal-type repair. However, previous fetal studies have inconsistently reported the degree of TGF-beta induction after injury. To minimize developmental variables in fetal versus adult TGF-beta regulation, we narrowed our study to wounded fetal animals. We hypothesize that TGF-beta ligand and receptor expression will be differentially regulated during the transition from early gestation (E16) wounds manifesting scarless fetal-type repair to late gestation (E19) wounds manifesting adult-type repair with scar. In this study, decreased and rapidly cleared TGF-beta 1 and -beta 2 expression accompanied by increased and prolonged TGF-beta 3 levels in wounded E16 animals correlated with organized collagen deposition. In contrast, increased and prolonged TGF-beta 1 and -beta 2 expression accompanied by decreased and delayed TGF-beta 3 expression in wounded E19 animals correlated with disorganized collagen architecture. Similarly, expression of TGF-beta receptors type I and II were also increased or prolonged in E19 animals. Our results implicate increased TGF-beta 1, -beta 2, and decreased TGF-beta 3 expression, as well as increased type I and II receptor expression in late gestation fetal scar formation.     

Cardiac Myxoma: Histochemical and Ultrastructural Localization of Glycosaminoglycans and Proteoglycans

A recurrent cardiac myxoma is examined histochemical ly at the ultrastructural level. By routine electron microscopy the stellate “myxoma” cell exhibits features suggestive of a secretory function in synthesis of its myxoid stroma. Spicer's high iron diamine (HID), which stains specifically for sulfated glycoconjugates, is utilized for intracellular localization of glycosaminoglycans. HID-positive reactive sites are localized within the Golgi-derived vacuoles and secretory granules of the myxoma cells. No staining is obtained with other cytoplasmic organelles except rare secondary lyso-somes. Although colloidal iron is less specific, both intracellular and extracellular positive reactive sites are observed. With ruthenium red staining the proteoglycans in the extracellular stroma can be visualized as numerous positively stained, polygonal 250-500 A matrix granules with faint filamentous projections. Positive intracellular ruthenium red-stained granules are also observed within the Golgi-derived vacuoles. The alcianophilia of the myxoid stroma with Alcian blue is almost completely abolished by prior treatment with bovine testicular hyaluronidase but is unaffected by leech hyaluronidase, indicating chondroitin sulfates A and/or C, not hyaluronic acid, as the major biochemical constituents of the stroma and the observed extracellular matrix granules. The above findings provide cytochemical evidence of intracellular synthesis of sulfated glycosaminoglycans and proteoglycans of the myxoma cell and its active participation in production of its stroma.     

Electrophysiological investigation of GABA-mediated inhibition at the hermit crab neuromuscular junction

1. The inhibitory neuromuscular junction of the abductor muscle of the large claw of the hermit crab (Eupagurus bernhardus) was investigated using electrophysiological intracellular techniques in order to elucidate further the relative contributions of the pre- and post-synaptic mechanisms of action of GABA and of neural inhibition.2. The electrical constants of the post-synaptic membrane, calculated using the equations for a `short cable'' model, were characteristic of a poorly developed electrical excitability; the specific membrane resistance was usually < 1000 Ω cm² and the specific membrane capacitance was > 40 μF/cm².3. Stimulation of the excitatory axon to the abductor muscle of the large claw at a frequency of 20 Hz evoked highly facilitating excitatory junction potentials (e.j.p.s); stimulation of the inhibitory axon (60-220 Hz) during the excitatory train elicited inhibition which was manifest as an attenuation of the e.j.p.s.4. The addition of γ-aminobutyric acid (GABA) to the bathing solution produced a dose-dependent reduction of e.j.p. amplitude and membrane resistance. The inhibitory effect of concentrations (5 × 10^-5 and 1 × 10^-4 M) which caused a 40-75% e.j.p. attenuation could largely be accounted for by a post-synaptic action on membrane conductance.5. Experiments with picrotoxin suggest that presynaptic inhibitory mechanisms have an important role in neurally evoked inhibition.6. Picrotoxin (1-5 × 10^-5 M) effectively blocked neural inhibition and the actions of GABA in this preparation, whereas bicuculline proved to be considerably less potent and therefore less useful as a physiological tool for studying GABA-mediated inhibition in crustacea.     

Ultrastructural Features of Epidermolysis Bullosa

Epidermolysis bullosa (EB), a heterogeneous group of hereditary diseases, varies in mode of inheritance, extent, severity, and presence or absence of scarring and dystrophy. Fourteen cases (13 in infants and 1 in a young adult) were studied. Subtyping by ultrastructural findings in normal and blistered skin biopsies was as follows: EB simplex (2), EB letalis (3), EBD dominant (2), and EBD recessive (7). One case diagnosed as recessive dystrophic by electron microscopy (EM) followed a benign course with little scaring and was re-classified clinically and after reviewing the EM as dominant dystrophic. Defining the level of bulla formation by EM allowed accurate diagnosis of subtypes. In 6 patients with EBD recessive, normal and bullous skin showed collagenolysis and no anchoring fibrils. In patients with EBD dominant, rudimentary fibrils were noted in normal skin. Whether absence of anchoring fibrils is primary or secondary in these two types and the role of collagenolysis remain unresolved.     

The influence of chloride on the ouabain-sensitive membrane potential and conductance of crayfish giant axons

1. Resting potential and current-voltage relation were measured in crayfish giant axons bathed in chloride-free and sodium-free solutions with and without ouabain. 2. Chloride-free solution caused a transient depolarization but did not alter the steady-state membrane potential. Utilizing isethionate as an anion substitute, the membrane resistance increased 12.5%. 3. In the absence of extracellular chloride, ouabain (0.5-1 mM) depolarized the axon 6-7 mV. The shape of the current-voltage relation did not change but the curve was shifted along the current axis. 4. These results indicate that ouabain inhibits a steady-state hyperpolarizing electrogenic pump current of approximately 3 muA/cm2. 5. Extracellular sodium removal from axons equilibrated in chloride-free solutions transiently hyperpolarized the membrane 6-7 mV without a change in membrane resistance. The transient hyperpolarization was ouabain and temperature sensitive. The steady-state potential reached in sodium-free and chloride-free solution was not ouabain sensitive. Temperature sensitivity of the steady-state membrane potential was greatly reduced. 6. The transient hyperpolarization produced by extracellular sodium removal was metabolically driven and may present the expression of a sodium efflux transport current of 7.0-7.5 muA/cm2. 7. Using electrophysiologically measured parameters, sodium and potassium conductance, influx and efflux currents and the coupling ratio for sodium/potassium transport are calculated from a modification of the conductance equation. 8. The sodium/potassium transport coupling ratio for steady-state conditions was estimated at 5:3 (1.67:1).