Distribution of elements in rabbit liver lobule

The elemental composition of rabbit liver was determined by the PIXE and micro-PIXE methods. The mean concentrations of P, S, Cl, K, Fe, Cu, Zn, and Rb measured by both methods were similar. The latter method also allowed for localization of elements within lobule territory. It has been found that some elements are more prevalent in the veins (Cl, Fe) and others in the liver parenchyma (P, Cu, Zn). Moreover, Zn showed the characteristic intralobular distribution. Some methodological aspects of microbeam application to biological materials were also discussed.     

Commissural ring nerve: A female-specific neurosecretory tract supplied by bifurcating median neurons in the cockroach Periplaneta americana (L.) and the cricket Teleogryllus commodus (Walker)

Summary In the American cockroach, Periplaneta americana, and the Australian field cricket, Teleogryllus commodus, the two nerves supplying the bases of the cerci are joined by a branch that crosses behind the last abdominal ganglion. This commissural ring nerve is restricted to females, and it contains many axons filled with granular and agranular vesicles. The axons stem from somata located within the ganglion. There are one (Periplaneta) or two (Teleogryllus) groups of median neurons with bilaterally symmetrical bifurcations, and a group of postero-ventral neurons on each side. In T. commodus, these neurons are distinct from others associated with the cerci. In the two species, the ring nerve neurons contribute to a neuropile near the root of each cereal nerve. The bifurcating median neurons arborize on both sides before entering the ring nerve, while the postero-ventral ones branch more extensively ipsilateral to their somata. The possibilities are discussed that the bifurcating neurons may be homologous to dorsal unpaired median neurons, and that the ring nerve may be a neurohemal area.     

Regulation of Brain and Cerebrospinal Fluid Calcium by Brain Barrier Membranes Following Vitamin D-Related Chronic Hypo- and Hypercalcemia in Rats

Male Fischer-344 rats, 21 days old, were fed diets containing 0 (LOD), 2,200 (CONT), or 440,000 (HID) international units of vitamin D3 per kilogram for 12 weeks. [Ca] was measured in plasma, CSF, brain, and choroid plexus. In addition, 45Ca and 36Cl transfer coefficients (KCa and KCl) for uptake from blood into CSF and brain were determined. Although plasma ionized [Ca]s in LOD and HID rats were 50% and 136%, respectively, of values in CONT animals, CSF and brain [Ca]s ranged from only 85% to 110% of respective CONT values. Choroid plexus [Ca] was increased by 37% after HID diet, but was decreased only 10% after LOD. KCa values at CSF, parietal cortex, and pons-medulla were negatively correlated with plasma ionized [Ca], whereas KCl values at CSF and brain were not different between the diet groups. The findings demonstrate that central nervous system [Ca] is maintained during chronic hypo- or hypercalcemia by saturable transport of Ca at brain barrier membranes. This transport does not seem to involve modulation by 1,25-dihydroxyvitamin D3.     

New observations on the Lower Carboniferous pteridosperm Diplopteridium Walton and an associated synangiate organ

New material of Diplopteridium holdenii is described from the Drybook Sandstone assemblage of Upper Visean (Middle Mississippian) age at Puddlebrook, Gloucestershire. Vegetative leaves consist of bifurcate fronds which are pinnately divided and terminate in narrow pinnule segments. The fronds are arranged spirally in terminal crowns on a narrow, spindly axis. Fertile leaves consist of fronds which bear a median, dichotomous branchlet which gives rise to reflexed, bilaterally symmetrical cupules. One specimen demonstrates that a single fertile crown consisted of cupulate and vegetative fronds. The detailed morphology of the cupules is reconstructed from compression/impression and fusainized material from both attached and isolated units. An isotomously branched synangiate organ is also described from the locality. The synangiate organ is assigned to a new genus and species. A comparison of D. holdenii and this synangiate organ with Diplopteridium teilianum from north Wales and Sphenopteris bifida and Sphenopteris affine from northern England and Scotland, provides indirect evidence that the synangiate organ may have belonged to D. holdenii . Bifurcate and trifurcate fronds associated with dichotomous branchlets bearing either synangial or cupulate structures was a common association in the Visean compression assemblages of Great Britain.     

蚱蝉的发声器结构:中纵隔膜

在雄蚱蝉(Cryptotympana atrata Fabricius)的体内,作者发现了白色略透明,并富有弹性的蝉体内最大的薄膜.厚约3.5μm,面积50.7mm²左右.该膜被称为中纵隔膜.中纵隔膜位于大气管气囊的矢状面,把大气囊分为相等的左右二气室,每个气室的容积约为700mm³.以中纵隔膜为界,雄蚱蝉有左右两个发声器,这两个发声器的结构相同,对称并相对独立.文中讨论了中纵隔膜在蝉鸣的发声和共振中的作用.蚱蝉自鸣声是在神经系统的控制下,由左右两个发声器协调工作发出的.在腹部共振中,中纵隔膜的振动为其中之一,比腹节的振动开始得早.     

Passive immunization protects guinea pigs from lethal toxoplasma infection

Abstract The cellular and humoral interactions that contribute to protective immunity in toxoplasmosis were studied by adoptive transfer of selective cell populations or immune serum and its fractions into normal syngeneic strain 2 guinea pigs. The results of this study with the RH strain of Toxoplasma gondii confirm and extend the findings of previous studies by showing that the passive transfer of parasite-sensitized T cells or of immune serum from previously infected donors protected recipient guinea pigs against lethal toxoplasmosis. An additional key finding was that similar levels of complete protection against lethal infection occurred in guinea pigs receiving partially purified anti- Toxoplasma immunoglobulins or immune cells that had been enriched for B cells prior to transfer. Cells residing in the spleen, lymph nodes and peritoneal cavity, but not the thymus, were equally effective in conferring immunity to challenged recipients. In addition, cell titration experiments revealed that guinea pigs could survive T. gondii infection by infusing them with as little as 2 × 10⁷ sensitized T cells or B cells. Unlike protection mediated by T cells, protection against lethal disease occurring in the B cell recipients was associated with the formation of Toxoplasma antibodies. These findings illustrate the major role of both humoral and cell-mediated immunity in affording protection against toxoplasmosis based on a guinea pig model of the human disease.     

Effect of atropine on plasma gastrin and somatostatin concentrations during sham feeding in man

The purpose of these studies was to measure circulating gastrin and somatostatin concentrations during sham feeding in humans and to evaluate the effect of two doses of intravenous atropine on circulating concentrations of these peptides. Gastric acid and bicarbonate secretion and pulse rate were also measured. Sham feeding increased plasma gastrin concentrations by approximately 15 pg/ml but had no effect on plasma somatostatin-like immunoreactivity (SLI). A small dose of atropine (5 micrograms/kg) augmented plasma gastrin concentrations during sham feeding significantly (P less than 0.01), but did not affect plasma SLI. Atropine also significantly inhibited gastric acid secretion and gastric bicarbonate secretion (by 62% and 52%, respectively), but pulse rate was not affected. A larger dose of atropine (15 micrograms/kg intravenously) suppressed plasma gastrin concentrations significantly compared to the smaller 5 micrograms/kg atropine dose (P less than 0.02), so that plasma gastrin concentrations when 15 micrograms/kg atropine was given were not significantly different from those during the control study. 15 micrograms/kg atropine reduced gastric acid and bicarbonate secretion by 81% and 66%, respectively, and also increased pulse rate by 15 min-1. These studies indicate that small doses of atropine enhance vagally mediated gastrin release in humans, probably by blocking a cholinergic inhibitory pathway for gastrin release. Although the nature of this cholinergic inhibitory mechanism is unclear, we found no evidence to incriminate somatostatin. Our finding that the larger dose of atropine reduced serum gastrin concentrations compared with the smaller dose suggests that certain vagal-cholinergic pathways may facilitate gastrin release.