The appearance of oestrone sulphate in the peripheral plasma of the pig early in pregnancy

Detectable concentrations of oestrone sulphate were present in 50% of the plasma samples collected from pregnant animals by Day 17. No oestrone sulphate was detected in plasma from cyclic nonpregnant pigs.     

How do floater male eastern bluebirds benefit by filling vacancies on territories where females already have young?

When male eastern bluebirds (Sialia sialis) are killed or deserttheir mates, replacement males usually take over the territory.We captured 25 eastern bluebird males and held them in captivityto study the behavior of replacement males and their responseto young already present in the nest. Of 17 replacement males,most courted the females, and 23% of experimental females renested,a proportion not different from that of control females. Noreplacement males were infanticidal, and none fully adoptedthe young. Replacement males spent significantly less time onthe territory and defended it significantly less than controlmales. We discuss breeding options available to a floater maleeastern bluebird and conclude that (1) floater male bluebirdsthat fill territory vacancies benefit by gaining breeding opportunitiesin the current breeding season, and (2) indifference to theyoung is the least costly option for replacement male easternbluebirds.     

EVIDENCE FOR POLLINATION ECOTYPES IN THE YELLOW-FRINGED ORCHID,PLATANTHERA CILIARIS

Platanthera ciliaris is a butterfly-pollinated, terrestrial orchid with a loose terminal raceme of 10–50 orange flowers, characterized by a long nectariferous spur. In the southeastern United States, P. ciliaris occurs in the Appalachian mountains and coastal-plain physiographic provinces, but it is found rarely in the intervening Piedmont. In 1983 and 1984, detailed observations of two populations within these disjunct areas revealed that the butterfly species that serve as the primary pollinators differ sharply. In the mountains, Papilio troilus (spicebush swallowtail) was the most frequent and effective visitor, whereas in the coastal plain, P. palamedes (palamedes swallowtail) was the predominant pollinator. Proboscis lengths of P. troilus (mean = 23.3 mm) were significantly shorter than those of P. palamedes (mean = 28.7 mm). Floral characters, most notably spur length, also differed significantly between mountain (mean = 23.8 mm) and coastal-plain (mean = 25.6 mm) plants. In both 1983 and 1984, levels of pollinator service, as assessed by rates of removal and insertion of pollinia, were higher in the mountains (0.81 and 0.86) than in the coastal plain (0.63 and 0.67). In addition, fruit-set was significantly greater in mountain (83.9% in 1983, 86.5% in 1984) than in coastal-plain (63.8% in 1983, 65.5% in 1984) populations. We hypothesize that selection pressure exerted through pollinator proboscis lengths has resulted in pollination ecotypes of P. ciliaris. The short-spurred mountain plants appear to be in equilibrium with their short-tongued butterfly pollinators, receiving high levels of effective pollination and achieving high levels of fruit-set. Coastal-plain plants produce flowers with longer spurs which, nevertheless, are shorter than optimal for insuring that very long-tongued butterflies make contact with their pollinia. Thus, effective pollinator service and fruit-set are reduced. Correlation analyses in 1984 showed a positive relationship between spur length and fruit-set only in the coastal plain. The presence of long-tongued nectar thieves in the coastal plain may also contribute to lower effective pollinator service and fruit-set. Results of reciprocal-transplant studies attempting to determine the genetic basis of floral characters, including spur length, were inconclusive but suggest that differences between mountain and coastal-plain plants are not due solely to phenotypic plasticity.     

On gap junction structure

We have studied the stain distribution within rat liver gap junctions for specimens prepared by thin sectioning and negative staining. Pools of stain molecules exist in two specific locations with respect to the distinctive morphological units (connexons) of the junction. One pool of stain surrounds the connexons and is restricted to the extracellular space in the gap between the adjacent plasma membranes. The other pool of stain is located along in the central axis of each connexon, measures 1-2 nm in diameter and 4-5 nm in length, and is restricted to the gap region. On rare occasions, barely discernible linear densities seem to extend from this latter pool of stain and traverse the entire width of the junction. The data indicate the existence of a hydrophilic cavity along the central axis of te connexon which, in most instances, is restricted to the gap region. However, the precise depth to which this cavity may further extend along the connexon axis is still uncertain.     

The structure and function of the labrum in the lobster Homarus gammarus (L.).

The labrum of decapod crustaceans is a soft lobe overhanging the mouth. The labral skeleton, musculature and innervation of Homarus gammarus are described. There are three bilateral groups of sensory neurons innervating the floor, lobe and lateral walls of the labrum. These are probably responsible for the phasic afferent activity that can be recorded from the inner labral nerve on mechanical deformation of the labrum. The labrum undergoes rhythmical retraction-protraction movements during ingestion and is shown to be active during both mandibular activity and oesophageal peristalsis. Studies were made on the duration and frequency of labral "swallowing" activity. The role of the labrum in feeding is discussed.     

Excess smoking in malignant-phase hypertension

The smoking habits of 82 patients with malignant-phase hypertension were compared with those of subjects in three control groups matched for age and sex. Sixty-seven (82%) of the patients with malignant-phase hypertension were smokers compared with 41 (50%) and 71 (43%) of the patients in two control groups with non-malignant hypertension, and 43 people (52%) in a general population survey. The excess of smokers in the malignant-phase group was significant for men and women, together and separately, for cigarette smoking alone, and for all forms of smoking. There were no significant differences between the control groups. The chance of a hypertensive patient who smoked having the malignant phase was five times that of a hypertensive patient who did not. Twelve patients in the malignant-phase group had never smoked. All were alive three and a half years on average after presentation (range 11 months to seven years). Twenty-four (36%) of the smokers with malignant-phase hypertension died during the same period. The mortality rate was significantly higher among patients with renal failure, as was the prevalence of smoking. Eighteen patients with malignant-phase hypertension had a serum creatinine concentration higher than 250 μmol/l (2·8 mg/100 ml); 17 were smokers and one an ex-smoker. Eleven of these 18 patients died.It is concluded that hypertensive patients who smoke are much more likely to develop the malignant phase than those who do not, and that once the condition has developed it follows a particularly lethal course in smokers.     

The synthesis of DNA by DNA-membrane complexes from irradiated E. coli B/r and Bs-1: the role of the membrane.

DNA-membrane complexes were isolated from lysed E. coli B/r and Bs-1, either by low g forces from a low salt solution, or by high g forces through a discontinuous sucrose gradient. The latter method was more gentle. Irradiation of the intact bacteria had no effect on the membrane macromolecules or on RNA components of these complexes. DNA loss was not significant after irradiation under anoxic conditions but complexes isolated from from Bs-1 irradiated in air showed an appreciable decrease in DNA content. In the presence of the appropriate nucleotide mixture, both 'free' DNA, found in the supernatant fractions, and rapidly sedimented membrane-associated DNA were able to synthesize DNA in the absence of added polymerase. DNA synthesis associated with 'free' DNA was more sensitive to radiation than that associated with DNA bound to the membrane, which appeared to moderate the effects of radiation on new DNA synthesis. It is concluded that the depression of DNA synthesis is primarily a result of irradiation-induced changes on genome-DNA. The interpretation of earlier work from our laboratories that DNA-membrane complexes contained the macromolecular structure which responded to radiation with a high o.e.r. is not supported by the evidence in this work.