Modulation of the lobster pyloric rhythm by the peptide proctolin

The modulation of the pyloric network of the stomatogastric ganglion (STG) of the lobster Panulirus interruptus by the neuropeptide proctolin is described. First, the effects of proctolin on the pyloric motor patterns were characterized in terms of frequency and phase relations. Pyloric cycle frequency and lateral pyloric (LP) neuron activity increased and ventricular dilator (VD) neuron activity decreased with increasing concentrations (10(-9)-10(-6) M) of applied proctolin. Next, the effects of proctolin on the individual neurons that constitute the pyloric network were determined. Identified neurons were isolated from chemical and electrical presynaptic inputs by using pharmacological agents (Marder and Eisen, 1984a) and/or photoinactivation following Lucifer yellow injection (Miller and Selverston, 1979). Proctolin increased the amplitude and frequency of bursts produced by isolated pacemaker anterior burster (AB) neurons. Isolated LP and pyloric (PY) neurons responded to proctolin with increases in activity only when they were at or above threshold. All other pyloric neurons were unaffected. To determine how the direct effects of proctolin on isolated neurons resulted in the observed changes in frequency and phase relations in the motor pattern of the intact pyloric circuit seen in proctolin, individual neurons were deleted from the circuit. A comparison of proctolin's effects on isolated neurons with those on the intact network shows that the synaptic connectivity among neurons directly affected by proctolin and those unaffected by it shapes the network's response to proctolin.     

Occult breast cancer: prevalence and radiographic detectability

The radiographic detectability of occult breast cancer has been difficult to determine. A prospective study of breast disease was carried out that involved the performance of subcutaneous mastectomies in 519 consecutive cases of traumatic or initially unexplained death in New Mexico. Routine mammograms and radiographs of 1-cm specimens were obtained. At least 18 biopsies were performed in each subject. Carcinoma was identified in ten subjects; one subject had metastatic carcinoma from the lung, and two subjects had bilateral breast cancer, for a total of 11 breast cancers identified with microscopic examination. Two of the cancers were seen on whole-breast mammograms, and six were seen on radiographs of thin-section specimens. Four of the 11 breast cancers were apparent only on histologic study of breast tissue that was not suggestive of malignancy. No cancer was found in subjects under the age of 39 years. Five carcinomas were found in the 40-69-year age group; six were found in the 70-year and over age group. No correlation was noted between the radiographic Wolfe parenchymal patterns and the prevalence of breast cancer.     

Determination of alveolar epithelial cell phenotypes in fetal sheep: evidence for the involvement of basal lung expansion

The factors that control the differentiation of alveolar epithelial cells (AECs) into type-I and type-II cells in vivo are largely unknown. As sustained increases in fetal lung expansion induce type-II AECs to differentiate into type-I cells, our aim was to determine whether reduced fetal lung expansion can induce type-I AECs to trans-differentiate into type-II AECs. Chronically catheterised fetal sheep were divided into two age-matched control groups and three experimental groups (   n = 5  for each). The experimental groups were exposed to either: (1) 10 days of increased lung expansion induced by tracheal obstruction (TO), (2) 10 days of TO followed by 5 days of reduced lung expansion induced by lung liquid drainage (LLD), or (3) 10 days of TO followed by 10 days of LLD. Following 10 days of TO, 5 days of LLD reduced the proportion of type-I AECs from 89.4 ± 0.9 % to 68.4 ± 2.8 %, which was similar to control values (64.8 ± 0.5 %), and increased the proportion of type-II AECs from 1.9 ± 0.3 % to 21.9 ± 2.8 %, which remained below control values (33.4 ± 1.7 %). The same treatment increased surfactant protein (SP)-A, SP-B and SP-C mRNA levels (expressed as a percentage of control values) from 26.7 ± 6.0 %, 40.0 ± 7.3 % and 10.3 ± 1.8 % to 78.1 ± 10.3 %, 105.8 ± 12.7 % and 121.0 ± 14.1 %, respectively. Similar results were obtained after 10 days of LLD, which followed 10 days of TO. These results indicate that the phenotypes of type-I and type-II AECs are strongly influenced by the basal degree of lung expansion in fetal sheep. Furthermore, the coincident increase in type-II AEC proportions and SP mRNA levels in response to LLD suggests that type-I AECs can trans-differentiate into functional type-II cells, and hence are not terminally differentiated.     

An appraisal of methods used in the examination of retail samples of cows milk.

The use of the methylene blue test for the examination of cows milk was investigated in an inter-laboratory survey. A poor relationship was found between results of these tests and total viable counts. Coliforms were detected in a large number of pasteurized milks, indicating frequent post-pasteurization contamination. No relationship was found between the results of the methylene blue test and the presence of coliforms. Results from this survey highlight the need for reappraisal of the methylene blue test as a statutory method for the examination of milk. A total viable count and coliform test are suggested for providing information regarding dairy hygiene and the quality of the product at the point of retail sale.