Ovarian response to hCG treatment during the oestrous cycle in heifers

The aims of this study were to investigate whether treatment with a single ovulatory dose of hCG, between the day of oestrus and the end of the luteal phase, could induce extra ovulations in heifers and whether the presence of an existing corpus luteum (CL) affected the response. Heifers (N = 32) were injected with 1500 i.u. hCG or saline on a given day of the oestrous cycle. Treatments were repeated during subsequent cycles to provide a total of 71 observations, 57 of which followed an injection of hCG, given between Day 0 (oestrus) and Day 16, and 14 of which followed saline injections as controls. Ovulatory responses were noted by laparoscopy 2 days after hCG treatment. No heifers injected with saline produced additional CL. Of the hCG-treated cycles, 23 resulted in the formation of an additional CL, and this was significantly affected by the stage of the oestrous cycle when hCG was given; a greater response was observed during the early (Days 4-7) and late (Days 14-16) stages of the luteal phase than at the mid-luteal phase of the oestrous cycle. Two heifers were also treated with hCG on Days 17 or 18 of the oestrous cycle, but before oestrus; both had induced CL. There were no significant differences between the left-right orientation of the existing CL or the hCG-induced CL. These results demonstrate that the large, luteal-phase follicle of the cow is capable of ovulating in response to hCG and that the induced CL is not affected by the presence of an existing CL.     

Dilator actions of endothelin in coronary resistance vessels and the abdominal aorta of the guinea pig

Endothelin has been characterized as a potent constricting factor. The purpose of this study was to investigate possible dilator effects of this peptide and to examine whether dilator responses occur through an endothelium-mediated mechanism in guinea pig coronary resistance vessels and isolated aortic rings. Changes in perfusion pressure after bolus injections of endothelin were measured using a constant-flow modified Langendorff preparation with a transducer between the flow pump and the heart. An immediate fall in perfusion pressure, averaging 6 mmHg, was observed after injection of endothelin (10(-14)-10(-12) moles). This effect was maximal at 1 minute and tended to return toward baseline levels within 4 minutes. In response to endothelin (10(-9) M), isolated aortic rings relaxed 35% after being contracted with prostaglandin F2 alpha (10(-7) M). In both preparations, dilation was converted to constriction after endothelium damage by oxygen radicals or endothelium removal (mechanical rubbing). Dilator responses to endothelin were blocked by pretreatment for 30 minutes with indomethacin (14 microM) in the presence of an intact endothelium in coronary resistance vessels, whereas in the abdominal aorta they were not. We conclude that endothelin has significant dilator properties and that this effect is opposed by its constrictor action at higher doses. In addition, dilator responses to endothelin require an intact endothelium in both coronary vessels and abdominal aorta. Finally, endothelin-induced dilation in coronary resistance vessels appears to occur through a cyclooxygenase product-mediated mechanism.     

A marine and terrestrial Sirius Group succession, middle Beardmore Glacier-Queen Alexandra Range, Transantarctic Mountains, Antarctica

A succession of Sirius Group glacigene sediments which crop out along the western margins of the Beardmore valley between Cherry Icefall and Hewson Glacier, below The Cloudmaker, is designated as the stratotype of the Cloudmaker Formation. This new formation overlies a multiply glaciated pavement (Dominion Erosion Surface) cut into the Precambrian Goldie Formation, and is disconformably overlain by the Meyer Desert Formation (Sirius Group). The Cloudmaker Formation comprises bedded and massive diamictons, bedded sands and silts, and laminated clays. Assemblages of foraminifera occur throughout the Cloudmaker Formation and indicate that these basal Sirius Group sediments were deposited in brackish glacial marine environments. The general absence of diatoms suggest these marine waters were ice-covered. Similar marine assemblages are also present in basal Sirius Group sediments at Oliver Bluffs, Dominion Range. Recycled marine diatom assemblages in the Sirius Group at the latter locality indicate that the host sediments have an age of < 3.8 Ma (Pliocene). The Cloudmaker Formation is placed in the Pliocene, although a latest Miocene age for the basal sediments cannot be ruled out.Stratigraphie, sedimentologic, and paleontologic evidence suggests that Beardmore valley was occupied by a fjord and tidewater glacier system that extended at least 165 km through the Transantarctic Mountains from the southwestern Ross Sea. The stratigraphy of The Cloudmaker Formation consists of a succession of members separated by disconformities. It is hypothesised that these strata were deposited by a dynamic valley glacier system that underwent a history of glacier advance and grounding alternating with glacier retreat and flotation over a marine water column. A combination of fjord basin sediment filling and sea-level oscillations may also have influenced the pattern of glacier ice advance and retreat within Beardmore Paleofjord. The marine Cloudmaker Formation is overlain by the terrestrial diamicton dominated Meyer Desert Formation. At Oliver Bluffs, the Meyer Desert Formation diamictons are interbedded with fluvial, and lacustrine sediments; successions that contain in situ vascular plant fossils (principally the Southern Beech Nothofagus), mosses, and beetle remains. A Magellanic-type flora and fauna occupied the coastal margins of the Beardmore Paleofjord. The vertical transition from the basal marine Cloudmaker Formation to terrestrial Meyer Desert Formation provides a sea-level datum that can be used to assess the extent of post-Sirius Group tectonic uplift. Uplift rates at the Cloudmaker section, 90 km inland from the Transantarctic Mountain front or rift shoulder margin in the Queen Alexandra Mountain block are determined to be ~ 429 or ~ 350 m/Myr. This assumes a total uplift of 1331 m for the uppermost marine sediments of the Cloudmaker Formation, and maximum diatom-based ages for the Sirius Group of < 3.1 Ma or < 3.8 Ma. Gross similarities in stratigraphy and interpreted paleoenvironments are apparent between The Cloudmaker succession (Beardmore Paleofjord) and the upper Miocene-Pliocene successions at the mouth of Taylor Paleofjord, 800 km to the north. Contrasting present day elevational settings for these two widely separated marine successions indicates the post-Sirius rate of tectonic uplift for the Transantarctic Mountains has been significantly greater in the Queen Alexandra block.     

Mechanical and structural properties underlying contraction of skeletal muscle fibers after partial 1-ethyl-3-[3-dimethylamino)propyl]carbodiimide cross-linking.

We show prolonged contraction of permeabilized muscle fibers of the frog during which structural order, as judged from low-angle x-ray diffraction, was preserved by means of partial cross-linking of the fibers using the zero-length cross-linker 1-ethyl-3-[3-dimethylamino)propyl]carbodiimide. Ten to twenty percent of the myosin cross-bridges were cross-linked, allowing the remaining 80-90% to cycle and generate force. These fibers displayed a well-preserved sarcomeric order and mechanical characteristics similar to those of intact muscle fibers. The intensity of the brightest meridional reflection at 14.5 nm, resulting from the projection of cross-bridges evenly spaced along the myofilament length, decreased by 60% as a relaxed fiber was deprived of ATP and entered the rigor state. Upon activation of a rigorized fiber by the addition of ATP, the intensity of this reflection returned to 97% of the relaxed value, suggesting that the overall orientation of cross-bridges in the active muscle was more perpendicular to the filament axis than in rigor. Following a small-amplitude length step applied to the active fibers, the reflection intensity decreased for both releases and stretches. In rigor, however, a small stretch increased the amplitude of the reflection by 35%. These findings show the close link between cross-bridge orientation and tension changes.     

Disparate modulation of plasma membrane protein lateral mobility by various cell permeabilizing agents

The mobility of a cell surface protein on cells osmotically swollen by treatment with several different cell permeabilizing agents retains specific restraints despite detachment of the plasma membrane from the cortical cytoskeleton. Fluorescence photobleaching recovery experiments indicate that the lateral diffusion constants of immunoglobulin E (IgE)-receptor complexes on the surface of rat basophilic leukemia cells increase 2–5 × following permeabilization with streptolysin O or digitonin, with little change in their mobile fractions. Swelling by hypo-osmotic treatment in water enhances lateral diffusion of IgE-receptor complexes and raises the mobile fractions to near 100%. In contrast, swelling by treatment with filipin arrests lateral diffusion, although rotational mobility remains unhindered. Lateral mobility of a fluorescent lipid analogue remains unchanged under these conditions. Crosslinking by anti-IgE antibodies redistributes the IgE-receptor complexes into large patches on untreated cells and on cells swollen by permeabilization with streptolysin O or digitonin, but rot on cells swollen by treatment with filipin. The results indicate a diversity of effects of the various permeabilizing agents on the mobility of membrane proteins. In particular, treatment with filipin appears to reorganize the plasma membrane into a network of fluid domains on a scale smaller than the bleaching spot size used (～1.5 μm). © 1994 Wiley-Liss, Inc.     

B1 and B2 Bradykinin Receptors Encoded by Distinct mRNAs

Abstract: Bradykinin receptors have been subdivided into at least two major pharmacological subtypes, B₁ and B₂. The cDNAs encoding functional B₂ receptors have recently been cloned, but no molecular information exists at present on the B₁ receptor. In this article, we describe experiments examining the possible relationship between the mRNAs encoding the B₁ and B₂ types of receptor. We showed previously that the Human fibroblast cell line W138 expresses both B₁ and B₂ receptors. In this report, we describe oocyte expression experiments showing that the B₁ receptor in W138 human fibroblast cells is encoded by a distinct mRNA ∼2 kb shorter than that encoding the B₂ receptor. We have used an antisense approach in conjunction with the oocyte expression system to demonstrate that the two messages differ in sequence at several locations throughout the length of the B₂ sequence. Taken together with the mixed pharmacology exhibited in some expression systems by the cloned mouse receptor, the data indicate that B₁-type pharmacology may arise from two independent molecular mechanisms.     

Relation between infection with Helicobacter pylori and living conditions in childhood: evidence for person to person transmission in early life.

OBJECTIVES--To relate the prevalence of infection with Helicobacter pylori in adults to their living conditions in childhood to identify risk factors for infection. DESIGN--Prevalence study of IgG antibodies to H pylori (> 10 micrograms IgG/ml, determined by enzyme linked immunosorbent assay (ELISA)) and reported living conditions and other socioeconomic factors in childhood. SETTING--Three factories in Stoke on Trent. SUBJECTS--471 male volunteers aged 18 to 65 years. MAIN OUTCOME MEASURES--Seroprevalence and variables in childhood. RESULTS--Seroprevalence of H pylori increased with age (22/74 (29.7%) at < 30 years v 29/46 (63%) at 55-65 years; P < 0.001 for trend) and was related to manual occupation (14/65 (21.5%) for non-manual v 162/406 (39.9%) for manual; P = 0.003). After data were adjusted for age and occupation subjects from large families, whose childhood homes were crowded or who regularly shared a bed in childhood, were significantly more likely to be seropositive (adjusted odds ratio (95% confidence interval) 2.15 (1.41 to 3.30) for crowding and 2.13 (1.38 to 3.30) for sharing a bed), but there was no relation with possession of a bathroom, inside toilet, refrigerator, or household pets in childhood. CONCLUSIONS--Close person to person contact in childhood is an important determinant of seroprevalence of H pylori in adulthood, suggesting that the infection is transmitted directly from one person to another and may be commonly acquired in early life.