Tympanic and extratympanic sound transmission in the leopard frog

Summary The inner ear of the leopard frog,Rana pipiens, receives sound via two separate pathways: the tympanic-columellar pathway and an extratympanic route. The relative efficiency of the two pathways was investigated. Laser interferometry measurements of tympanic vibration induced by free-field acoustic stimulation reveal a broadly tuned response with maximal vibration at 800 and 1500 Hz. Vibrational amplitude falls off rapidly above and below these frequencies so that above 2 kHz and below 300 Hz tympanic vibration is severely reduced. Electrophysiological measurements of the thresholds of single eighth cranial nerve fibers from both the amphibian and basilar papillae in response to pure tones were made in such a way that the relative efficiency of tympanic and extratympanic transmission could be assessed for each fiber. Thresholds for the two routes are very similar up to 1.0 kHz, above which tympanic transmission eventually becomes more efficient by 15–20 dB. By varying the relative phase of the two modes of stimulation, a reduction of the eighth nerve response can be achieved. When considered together, the measurements of tympanic vibration and the measurements of tympanic and extratympanic transmission thresholds suggest that under normal conditions in this species (1) below 300 Hz extratympanic sound transmission is the main source of inner ear stimulation; (2) for most of the basilar papilla frequency range (i.e., above 1.2 kHz) tympanic transmission is more important; and (3) both routes contribute to the stimulation of amphibian papilla fibers tuned between those points. Thus acoustic excitation of the an uran's inner ear depends on a complex interac tion between tympanic and extratympanic sound transmission.Abbreviations dB SPL decibels sound pressure level re: 20 N/ m² - AP amphibian papilla - BP basilar papilla - BEF best excitatory frequency     

Characterization of the type of calcium channel primarily regulating GABA exocytosis from brain nerve endings

In an attempt to further characterize the type of Ca²⁺ channels primarily regulating GABA exocytosis, the effects of increasing concentrations of CTx MVIIC,--Aga IVA and other Ca²⁺ channel blockers (nitrendipine, Cd²⁺ and Ni²⁺), commonly used for pharmacologically discerning among the various types of Ca²⁺ channels, were tested on the dissected Ca²⁺ dependent fraction of the depolarization evoked release of GABA from mouse brain synaptosomes. Our results show that -CTx MVIIC inhibits GABA exocytosis with a calculated IC₅₀ of 3 M and -Aga IVA with a calculated IC₅₀ of 50 nM. The divalent cation Cd²⁺ only diminishes GABA exocytosis at 70 M, but does not modify this response at lower concentrations (i.e. 1 and 10 M). Neither nitrendipine (10 M) nor Ni²⁺ (100 M and 500 M) modified GABA exocytosis. The failure of nitrendipine at a high concentration to inhibit GABA exocytosis discards L-type Ca²⁺ channels as the main regulators of this response; likewise that of Ni²⁺ discards Ca²⁺ channels of the N-type, and the failure of nM concentrations of -CTx MVIIC or 500 M Ni²⁺, also discards alpha_1A/Q-type Ca²⁺ channels as the main regulators of the GABA response. On the basis of these results and in particular of the higher potency of -Aga IVA than -CTx MVIIC, it is concluded that the type of Ca²⁺ channels that primarily determine the exocytosis of GABA belong to a P-like type of Ca²⁺ channels.     

Electron-microscopic observations of the gravity receptor epithelia of normal and spinner juvenile Octopus maya

Summary Light and electron microscopy of the gravity receptor epithelia (maculae) of statocysts of normal and spinner juvenile Octopus maya showed differences between the structures of the hair cells, supporting cells, and afferent neurons of these cephalopods. The maculae of spinner animals were approximately 30% smaller in their surface area and had 40% fewer hair cells. Moreover, the average distance between randomly-chosen hair bundles in scanning electron micrographs of maculae of normal animals was significantly greater (4.33±6.47 m) than those of maculae of spinner animals (3.38±4.90 m; P<0.0001). The sectional area of the supporting cell's microvilli in spinners maculae was larger (0.16±0.18 m) than those of normal (0.10±0.10 m; P<0.0001) O. maya. The morphological differences observed between certain structural components of the maculae of normal and spinner O. maya may be related to the absence and/or malformation of the neuroepithelial suprastructures in spinners. This may have direct or indirect effects related to their inability to orient to gravity with these organs.     

Selection of rice for iron toxicity tolerance through irradiated caryopsis culture

A protocol for plant regeneration from caryopses of Indica rice via a callus phase was developed and adopted to select regenerants in media simulating iron toxicity. Caryopses of three commercial Sri Lankan rice cultivars (RU 102, LD 355 and AT 353) were induced to produce callus on MS medium supplemented with either 2,4-dichlorophenoxyacetic acid (2,4-D) or chlorophenoxyacetic acid (CPA), and 6-benzylaminopurine (BA). Plant regeneration was more efficient when 4-week-old calli induced using 9 M 2,4-D and 0.5 M BA were transferred to MS medium supplemented with 2.2 M BA and 0.6 M -naphthaleneacetic acid (NAA). Three concentrations of Fe, three pH levels and three doses of irradiation (0, 100 and 150 Gy) were used in the selection experiment. Varieties LD 355 and AT 353 were more responsive than RU 102 to callus induction and plant regeneration. Although high iron concentration in combination with low pH significantly decreased callus induction and plant regeneration efficiencies, irradiation of the explants did not have any effect on these parameters. Nevertheless, the height and seed yield of plants regenerated from calli of irradiated caryopses were significantly reduced in R₀M₁. The in vitro protocol developed for selecting rice mutants would be useful in supplementing the current breeding efforts to develop rice varieties tolerant to iron toxicity.     

Quantitative analyses of sex and size differences in the macula neglecta and ramus neglectus in the inner ear of the skate,Raja ocellata

Summary In Raja ocellata the macula neglecta is located in the posterior canal duct of the inner ear at the junction with the sacculus. The maximum length and width of a freeze-dried macula from a male skate of 61 cm width is 1035 m and 315 m respectively. Ultrastructural studies show that the hair cells of the macula are of two types. Orientation of hair cells is towards the periphery with a reverse direction of polarization in 5.0 to 6.5% of the cells. The axons of the associated nerve, the ramus neglectus, are myelinated, and include both efferent and afferent fibres.Electron-microscopic studies and quantitative analyses reveal significant sex differences in the macula neglecta and ramus neglectus. Hair cell and axon numbers, and total axon areas increase linearly with skate size, and are significantly different in males and females for any given representative size of skate, the females having the larger counts. Since the macula neglecta functions as a vibration detector of far-field localizations, the gender difference may be involved in the location of prey, or in mate detection. It is unknown whether such differences occur in any other vertebrate species.     

The Acoustical Biology of Elasmobranchs

A report on the auditory capabilities and their associated functions of elasmobranch fishes along with a brief review of the physics of underwater sound as it relates to hearing by fishes is provided. The inner ears of elasmobranchs possess structures that are no different from other fishes, except for an enlarged macula neglecta, which is unique among fishes. Hearing abilities among sharks (the only elasmobranchs examined) have demonstrated highest sensitivity to low frequency sound (40Hz to approximately 800Hz), which is sensed solely through the particle-motion component of an acoustical field. Free-ranging sharks are attracted to sounds possessing specific characteristics: irregularly pulsed, broad-band (most attractive frequencies: below 80Hz), and transmitted without a sudden increase in intensity. Such sounds are reminiscent of those produced by struggling prey. A sound, even an attractive one, can also result in immediate withdrawal by sharks from a source, if its intensity suddenly increases 20dB [10 times] or more above a previous transmission. Present evidence also shows that the lateral line system does not respond to normal acoustical stimuli. Morphological and physiological evidence suggest that the maculae neglecta possess acoustical relevance and may explain directionality of response despite physical principles that provide still other hypotheses for acoustical directionality. Brain centers controlling acoustical response, particularly among sharks, must be explored in the near future with careful consideration of the habits of subjects based on indications of species-differences regarding the importance of acoustical stimuli to their activities. Numerous facts and ideas about the acoustical biology of elasmobranch fishes make certain that future research will be most rewarding.     

Acoustic,auditory, and morphological divergence in three species of neotropical frog

Advertisement calls, auditory tuning, and larynx and ear morphology were examined in 3 neotropical frogs, Hyla microcephala, H. phlebodes and H. ebraccata, H. microcephala has the highest call dominant frequency (6.068 kHz) and basilar papilla tuning (5.36 kHz). H. phlebodes and H. ebraccata calls have lower dominant frequencies (3.832 and 3.197 kHz respectively) and basilar papilla tuning (2.79 and 2.56 kHz). The primary call notes of H. ebraccata are longer (181.6 ms) than those of H. microcephala (95.5 ms) or H. phlebodes (87.3 ms). Morphometric analysis suggests that temporal call features differ as laryngeal musculature changes, in the process changing the overall size of the larynx. The spectral aspects of the call differ as head size, and hence the size of its resonating and radiating structures, changes, modifying the dominant frequency of calls by accentuating their higher harmonics when head size decreases. Decreasing head size decreases the size of the middle and inner ear chambers, changing the mechanical tuning of the ear in the same direction as the change in dominant frequency. These changes result in divergent spectral-temporal characteristics of both the sending and receiving portions of the acoustic communication system underlying social behavior in these frogs.Abbreviations AP amphibian papilla - BEF best excitatory frequency - BP basilar papilla - dB SPL decibels sound pressure level re:20 N/m²     

Heterogeneous Long Chain Acyl-CoA Synthetases Control Distribution of Individual Fatty Acids in Newly-Formed Glycerolipids of Neuronal Cells Undergoing Neurite Outgrowth

Using PC12 cells undergoing neurite outgrowth, we studied the activation of various fatty acids, of different chain lengths and degrees of saturation, by long chain acyl-CoA synthetases (LCASs). Cells treated with nerve growth factor (NGF) were labeled with [³H]glycerol, [³H]oleic acid (OA) or [³H]arachidonic acid (AA) in the presence of other unlabeled fatty acids of endogenous or exogenous origin. Triacsin C (4.8 M), an inhibitor of acyl-CoA synthetase, decreased the incorporation of exogenous [³H]OA into glycerolipids by 30–90%, and increased by about 60% the accumulation of free [³H]OA in the cells. However it did not affect the incorporation of endogenous fatty acids nor of exogenous [³H]AA into phospholipids, suggesting that LCASs which activate exogenous AA and at least some endogenous fatty acids are relatively insensitive to this drug. Activities of the LCAS that is specific for AA (ACS), or of the non-specific LCAS which activates OA and other fatty acids (OCS), were much higher in microsomal and cytoplasmic fractions than in mitochondria or nuclei. The Vmax and Km values of ACS and OCS in microsomes were 12 and 0.7 nmol/min/mg protein and 70 and 37 M, respectively; and in cytoplasm, 6 and 0.6 nmol/ min/mg protein and 38 and 60 M, respectively. Triacsin C (2–33 M) did not affect ACS activity in microsomal or cytoplasmal fractions, but inhibited OCS activities dose-dependently and competitively: IC₅₀ and apparent Ki values were 13.5 M and 14 M in microsomes, and 3.8 M and 4 M in cytoplasm. NGF stimulated the activities of the LCASs, and, consistently, the incorporation of the various fatty acids into glycerolipids. These data indicate that LCASs are heterogeneous with respect to their intracellular locations, substrate specificities, kinetic characteristics and sensitivities to triacsin C; and that this heterogeneity affects the extents to which individual fatty acids are utilized to form glycerolipids.     

The gravity reference response,the rotation sensation,and other illusory sensations experienced in aircraft and space flight

An analysis of the gravitational and inertial forces which act during aircraft flight upon the vestibular systems of the aircraft occupants reveals that in the absence of a visual horizon, certain illusory sensations are predictable for various acceleration environments. Horizontal forward applied acceleration results in a climbing (backward tilting) sensation; conversely, horizontal rearward applied acceleration results in a diving (forward tilting) sensation. During any attempt to achieve weightlessness in aircraft parabolic flight, special care has to be taken to avoid unintended longitudinal (x-axis) accelerations. Recent flight tests established that the rotation sensation (Dzendolet, 1971; Gerathewohl, 1956) during entry into parabolic flight can be attributed to the existence of unintended longitudinal accelerations. However, the inversion illusion (Graybiel and Kellogg, 1966) felt by some human subjects at 0g seems to be different from the rotation sensation and could be caused by the diminished pressure forces of the otoliths on the maculae. The inversion illusion of man correlates well with the blind fish diving behavior observed during aircraft parabolic flight (von Baumgartenet al., 1969, 1972). It is suggested that the fish lowg diving response and the human inversion illusion are due to the substitution of a predominately shearing force of low magnitude as a vestibular reference in place of a normal, predominately pressure force. This hypothesis indicates that vestibular senses alone cannot provide meaningful postural orientation to simulated or actual gravity of a magnitude below that of Earth's gravity.This research was supported in part by NASA Contract NAS2-6057.G. L. Shillinger, Jr. is with the Flight Projects Development Division, Ames Research Center, NASA, Moffett Field, California.     

Die Kopfregeneration vonLineus sanguineus Rathke(Nemertini) unter dem Einfluβ von Actinomycin-D. Chemomorphologische Befunde

Zusammenfassung Isolierte Körperteile vonLineus sanguineus wurden in Seewasser gehalten, das unterschiedliche Konzentrationen (1,9, 0,95 und 0,48 g/ml) von Actinomycin-D enthielt. Nach 4, 5, 6 und 10 Tagen wurden die Regenerate histologisch und histochemisch (Glykogen, Glucose-6-phosphat-Dehydrogenase und RNS) untersucht. In Abhängigkeit von der Actinomycin-D-Konzentration werden bestimmte Phasen der Regeneration gehemmt; dabei sind Proliferationsprozesse weniger empfindlich als Differenzierungsprozesse. Histochemisch werden bei Hemmung der wachstumsaktiven Areale die im Normalfall zu beobachtenden stofflichen Merkmale: Glykogeneinlagerung und nachfolgender Anstieg der G-6-P-DH-Aktivität und der RNS-Konzentration vermißt.

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The head regeneration ofLineus sanguineus Rathke (Nemertini) under the influence of actinomycin-D. Chemomorphological data

Summary Fragments ofLineus sanguineus were incubated in seawater, which contained different concentrations of actinomycin-D (1.9 g/ml, 0.95 g/ml and 0.48 g/ml). After 4, 5, 6 and 10 days the regenerates were studied by histological and histochemical methods (glycogen, glucose-6-phosphate-dehydrogenase and RNA). Corresponding to actinomycin-D concentration certain phases of regeneration are inhibited. The phases of proliferation are less sensitive to actinomycin-D than the phases of differentiation. If morphogenetic areas are inhibited, the normally demonstrable histochemical characteristics: accumulation of glycogen and later, the increase of G-6-P-DH activity and RNA concentration do not appear.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Adiabatic compressibility and intrinsic viscosity studies on peptide aggregates

Density and sound velocity measurements and ¹H NMR investigations were carried out in aqueous solution at various temperatures for determining the adiabatic compressibility () and hydration of the tetrapeptide, TFA. Tyr-Gly-Phe-Ala-Obz I. The present investigation showed changes in the temperature coefficient of adiabatic compressibility at 40 °C. ¹H NMR studies indicated the inverse temperature transition in the concentration range studied.     

A new histo-and cytochemical method for demonstration of cyclic 3′, 5′-nucleotide phosphodiesterase activity in retinal rod photoreceptor cells of the rat

Summary Cyclic 3, 5-mononucleotide phosphodiesterase (cyclic nucleotide PDEase) activity was studied histo-and cytochemically in the retinal rod photoreceptor cells of the rat by means of a newly developed technique utilizing the intrinsic 5 nucleotidase activity instead of an exogenous 5 nucleotidase source (snake venom). Cyclic GMP and cyclic AMP were used as substrates. When cyclic GMP was used as a substrate, the intense activity of phosphodiesterase (PDEase) was distributed over the entire rod outer segments; reaction product was observed on the plasmalemma and on the disk membranes of the outer segments. A slight reaction was also observed on the plasmalemma of the inner segments. However, no precipitate was found in the perinuclear and synaptic regions of the rod photoreceptors. In contrast, when cyclic AMP was utilized as a substrate, a moderate reaction was seen in the synaptic region of the plexiform layer. The intensity of the reaction in the outer segments was much reduced in comparison to the results with cyclic GMP. The enzyme activity was almost completely inhibited by 2 mM 3-isobutyl-1-methylxanthine (IBMX) or 2 mM theophylline, which were potent inhibitors of PDEase.To confirm the propriety of our new cytochemical method, the localization of 5 nucleotidase was also studied utilizing 5 AMP or 5 GMP as substrates. In contrast to the activity of cyclic nucleotide PDEase, the activity of 5 nucleotidase was distributed on all membranes of the photoreceptors from the synaptic outer plexiform layer to the tip of outer segments. After inhibition of the intrinsic 5 nucleotidase activity with the use of 1 mM Ni-ions or 10 mM NaF no demonstration of cyclic nucleotide PDEase activity was possible; the existence of intrinsic 5 nucleotidase activity is necessary for the release of free phosphateions from 5 AMP (5 GMP), which are a prerequisite for the histochemical reaction. For comparison, some sections were incubated with the conventional cyclic nucleotide PDEase incubation medium containing snake venom from Ophiophagus hannah. With this conventional method, morphological preservation was extremely poor, and moreover, the reaction itself was weaker than that with the presently described method.The authors wish to dedicate the paper to Professor Dr.Dr.h.c. A. Oksche, Justus Liebig University Gießen     

Metal resistance in Pseudomonas strains isolated from soil treated with industrial wastewater

Heavy metal concentrations in soil treated with industrial wastewater of Aligarh City (U.P.), India were determined. The analysis of test samples revealed high levels of Fe, Zn, Ni and Cu. A total of 45 Pseudomonas spp. were isolated from soil and were characterized on the basis of morphological, cultural and biochemical characteristics. MICs of Hg²⁺, Cd²⁺, Cu²⁺, Cr³⁺, and Zn²⁺ for each isolate were determined. Eighty percent of the strains isolated from soil harboured resistance to copper, whereas 73.3% of the isolates exhibited resistance to cadmium, 71.1% to chromium and zinc and 48.8% to mercury. A maximum MIC of 200 g/ml for mercury and 1600 g/ml for other metals was observed. Metal resistance was found to be plasmid mediated as evidenced by transformation studies. Further, the transmissible nature of chromium resistance was confirmed by conjugation. Agarose gel electrophoresis using the miniprep method for plasmid isolation revealed that these isolates harboured plasmids of molecular weights (45 & 47 kb) using EcoRI and HindIII digests of DNA and undigested DNA as standard markers.     

Antioxidant Properties of New Chalcogenides Against Lipid Peroxidation in Rat Brain

Ebselen (2-phenyl- 1,2-benzisoselenazole-3 (2H)-one) is a seleno-organic compound with antioxidant properties, and anti-inflammatory actions. Recently, ebselen improved the outcome of acute ischemic stroke in humans. In the present study, the potential antioxidant capacity of organochalcogenide compounds diphenyl diselenide (PhSe)₂, diphenyl ditelluride (PhTe)₂, diphenyl disulfide (PhS)₂, p-Cl-diphenyl diselenide (pCl-PhSe)₂, bis-[S-4-isopropyl 2-phenyl oxazoline] diselenide (AA-Se)₂, bis-[S-4-isopropyl 2-phenyl oxazoline] ditelluride (AA-Te)₂ and bis-[S-4-isopropyl 2-phenyl oxazoline] disulfide (AA-S)₂ was compared with that of ebselen (a classical antioxidant). Spontaneous and quinolinic acid (QA)- (2 mM) and sodium nitroprusside (SNP)- (5 M)-induced thiobarbituric reactive species (TBARS) production by rat brain homogenates was determined colorimetrically. TBARS formation was reduced by ebselen, (PhSe)₂, (PhTe)₂, (AA-Se)₂, (AA-S)₂ and (pCl- PhSe)₂ to basal rates. The concentrations of these compounds needed to inhibit TBARS formation by 50% (lC₅₀) are 1.71 M, 3.73 M, 1.63 M, 9.85 M, > 33.3 M, 23.2 M and 4.83 M, respectively for QA. For TBARS production induced by SNP the lC₅₀ was 2.02 M, 12.5 M, 2.80 M, > 33.3 M, 24.5 M and 7.55 M, respectively. The compounds (AA-Te)₂ and (PhS)₂ have no antioxidant activity and pro-oxidant activity, respectively. These results suggest that (AA-Se)₂ and (AA-S)₂ can be considered as potential pharmaceutical antioxidant agents.     

Quantitative measurement of glucose-6-phosphate dehydrogenase in cortical fractions of the rabbit nephron

Summary A quantitative fluorimetric method is described for estimating the activity of glucose-6-phosphate dehydrogenase in isolated fractions of rabbit nephron from the superficial part of the renal cortex: macula densa, proximal convoluted tubule, distal convoluted tubule and glomerulus. The mean activity in the macula densa region was 2.5×10^–18 mol/m³/min, which was about twice the mean activity of the proximal and distal tubular cells and four times that of the glomeruli. As glucose-6-phosphate dehydrogenase is located in the cytoplasm, the average cytoplasmic enzyme activity of the different tubular cells was calculated: macula densa activity was 4.0×10^–18 mol/m³/min whilst proximal tubular cells showed about a third, and distal tubular cells about a quarter of this activity.     

Ontogeny of the antennal glands in the crayfish Astacus leptodactylus (Crustacea, Decapoda): anatomical and cell differentiation

The ontogeny of the antennal glands was studied during the embryonic and post-embryonic development of Astacus leptodactylus. The future glands arising from undifferentiated columnar cells were detectable at the metanauplius stage EI 150 m (EI: eye index; approximately 440 m at hatching). The tubule and labyrinth differentiated in embryos at EI 190 m, and the bladder and coelomosac at EI 250 m. At EI 350 m, the tubule lengthened and divided into proximal and distal sub-regions. In later stages, the gland retained the same morpho-anatomy but the differentiation and size of each part increased. The cells of the coelomosac displayed the cytological features of podocytes in late embryonic development at EI 440 m. Only small apical microvilli and a few mitochondria were observable in the labyrinth cells at EI 250 m; by EI 440 m, these cells presented well-shaped apical microvilli, formed bodies, basal infoldings and mitochondria. In the cells of the tubules and bladder, mitochondria and basal infoldings occurred at EI 440 m and EI 250 m, respectively. The differentiation of the tubules and bladder cells suggested that they were involved in active transport at EI 440 m. Following hatching, the differentiation of the cells and the size of the glands increased. The ontogeny of the antennal glands thus starts in early embryos, the specific cellular functional features being differentiated in the various parts of the glands by EI 440 m. The antennal glands are probably functional just before hatching, i.e., before the juveniles are confronted with the low osmolality of freshwater.Thanks are due to the University of Tarbiat Modarres and Ministry of Science, Research and Technology, Islamic Republic of Iran, for financial aid and support. Special thanks are also extended to the Société Française dExportation des Ressources Educatives (SFERE) for a scholarship to S.K.     

Auditory sensitivity of the cichlid fish Astronotus ocellatus (Cuvier)

Summary Auditory sensitivity was determined for the oscar, Astronotus ocellatus, a cichlid fish that has no known structural specializations to enhance hearing. Trained A. ocellatus behaviorally responded to sound stimuli from 200 Hz to 800 Hz with best sensitivity of 18 dB (re: 1 bar) to 21 dB for frequencies between 200 and 400 Hz. This is significantly poorer than hearing sensitivity for fish classified as hearing specialists, but well within the range of hearing capabilities reported for non-specialist teleost species.     

Growth and betacyanin production by hairy roots of Beta vulgaris in airlift bioreactors

Hairy roots of red beet (Beta vulgaris L.) were cultivated in different types of airlift bioreactors (cone, balloon, bulb, drum and column bioreactors of 5 l capacity and containing 3 l of half strength Murashige & Skoog medium). The cone type of airlift bioreactor gave the highest biomass of hairy roots and betacyanin accumulation. Betacyanin accumulation was 27 mg g^–1 dry wt in cultures aerated at 0.3 vvm. Light irradiation of 20 mol m^–2 s^–1 promoted hairy root growth but optimum betacyanin (34 mg g^–1 dry wt) accumulation was with the cultures grown under 60 mol m^–2 s^–1.     

Regeneration of plants from callus and embryos of ‘Royal’ apricot

Immature embryos of apricot (Prunus armeniaca L.) cv. Royal with a PF index of 25–100 were used to regenerate plants in vitro using two methods. In the first case, callus was initiated on MS medium with 4.5 M 2, 4-D plus 0.44 M BA and regeneration of shoots from the callus occurred on MS medium with 4.4 M BA plus 1.0 M 2, 4-D. In the second case, adventitious buds were directly regenerated from the cotyledons on MS medium with 4.4 M BA plus 1.0 M 2, 4-D.Abbreviations BA 6-benzyladenine - IBA dole-3-butyric acid - NAA -naphthylacetic acid - 2, 4-D 2, 4-dichlorophenoxyacetic acid - PF (embryo length/seed length) x 100     

A dual population of islets of Langerhans in bovine pancreas

Summary A morphological study of the bovine pancreas from fetus to adult documents the presence of two distinct types of pancreatic islets: large islets, 100 to 1600 m in diameter, enmeshed in interlobular connective tissue; small islets, 25–200 m in diameter, enmeshed in exocrine tissue. Large islets consisting primarily of well granulated B cells, decrease in relative volume with increasing age and in the adult are seldom seen. The overall relative volume of endocrine tissue is age dependent and ranges from 30% in the sixth month fetus to 10% in the neonate and 5% in the adult. Small islets contain B cells that increase their cytoplasmic secretory granularity with increasing fetal age, significantly degranulate just prior to birth and subsequently regranulate several weeks after birth. Beta cells of the small islets are uniquely characterized by junctional complexes in close association with large numbers of maculae adherentes (desmosomes). Using lanthanum-hydroxide and freeze-fracture techniques the junctional complexes are shown to consist of macula occludens (focal tight junctions) enclosing nexuses (gap junctions).The two types of islet differ in distribution, times of growth and times of B-cell granularity and may be indicative of functional differences yet to be elucidated.This work was presented in part at the Thirty-Fifth Annual Meeting of the American Diabetes Association, New York City, 1975