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Biomedical subjects

J L Ram

Publications and source records attributed to J L Ram.

67 records · Page 4Linked to original sources
PubMed1981

Serotonin has both excitatory and inhibitory modulatory effects on feeding muscles in Aplysia.

Serotonin (10(-8) M) produced opposite long-lasting (up to 10 min) effects on acetylcholine-elicited contractions of different buccal mass muscles of Aplysia. Contractions of the dorsal extrinsic muscle and accessory radula closer muscle were enhanced by serotonin; whereas contractions of the ventral extrinsic muscle were inhibited by serotonin. The effect of higher concentrations of serotonin on dorsal and ventral extrinsic muscles was in the same direction as at 10(-8) M but was greater in both magnitude and duration. The phase of feeding-protraction or retraction--during which a muscle is active--is not correlated with the direction of modulation produced by serotonin.

Animals↗
PubMed1977

Hormonal control of reproduction in Busycon: laying of egg capsules caused by nervous system extracts.

Mature specimens of female Busycon laid egg capsules when injected with extracts of nervous systems of male or female Busycon. The substance causing this behavior, named egg capsule laying substance (ECLS), was found most reliably in parietal ganglia, less consistently in cerebral-pleural ganglia, and rarely in other ganglia. Both species of Busycon found in Woods Hole, B. canaliculatum and B. carica, contained ECLS, and ECLS of each species was active in the other. ECLS activity was not destroyed by boiling for up to fifteen minutes. Centrifugation of nervous system extracts at 105,000 X g yielded ECLS only in the pellet. ECLS was not released from the pellet by freeze-thawing or by 1.0 M NaCl, but could be partially solubilized by boiling extracts before centrifugation. ECLS activity was destroyed by protease. Several animals "spontaneously" laid strings of egg capsules after being put in a group tank with males and other females. Approximately the first ten capsules laid by these animals were devoid of eggs, after which egg-containing capsules were laid. Injection of ECLS into a spontaneous egg layer within a few hours after cessation of spontaneous egg laying caused the laying of capsules containing eggs. The possibility that ECLS may normally be responsible for the laying of both eggs and egg capsules is discussed.

Animals↗
PubMedDate not supplied

Differences in alpha2-adrenoceptor modulation of calcium channels in vascular smooth muscle cells of male and female rats.

Effects of the alpha2-adrenergic agonist clonidine on current through Ca2+ channels was recorded from vascular smooth muscle cells isolated from tail arteries and aortae of male and female rats. The average Ba2+ current in control was not significantly different between males and females; however, clonidine (1 microM) enhanced Ba2+ current through Ca2+ channels in cells from females, but not from males. The greater sensitivity of vascular smooth muscle cells to clonidine may underlie different contractile responses to alpha2-adrenergic agonists between males and females.

Animals↗
PubMedDate not supplied

Using zebra mussels to monitor Escherichia coli in environmental waters.

Use of the zebra mussel (Dreissena polymorpha) as an indicator of previously elevated bacteria concentrations in a watershed was examined. The ability of the zebra mussel to accumulate and purge Escherichia coli over several days was investigated in both laboratory and field experiments. In laboratory experiments, periodic enumeration of E. coli in mussels that had been exposed to a dilute solution of raw sewage demonstrated that (i) maximum concentrations of E. coli are reached within a few hours of exposure to sewage, (ii) the tissue concentration attained is higher than the concentration in the ambient water, and (iii) the E. coli concentrations take several days to return to preexposure concentrations when mussels are subsequently placed in sterile water. In field experiments conducted in southeast Michigan in the Clinton River watershed, brief increases in E. coli concentrations in the water were accompanied by increases in mussel concentrations of E. coli that lasted 2 or 3 d. The ability of mussels to retain and to concentrate E. coli made it possible to detect E. coli in the environment under conditions that conventional monitoring may often miss. Sampling caged mussels in a river and its tributaries may enable watershed managers to reduce the sampling frequency normally required to identify critical E. coli sources, thereby providing a more cost-effective river monitoring strategy for bacterial contamination.

Animals↗
PubMedDate not supplied

Enumeration of waterborne Escherichia coli with petrifilm plates: comparison to standard methods.

Escherichia coli is often monitored in environmental waters as an indicator of the possible presence of human pathogens associated with feces. Petrifilm E. coli/coliform count plates (3M, Minneapolis, MN), previously validated for enumerating E. coli in food, were tested for monitoring E. coli in environmental water. Escherichia coli counts in environmental water samples enumerated with Petrifilm were significantly correlated (R > 0.9; slope = 0.9-1.0; p < 0.001) with counts obtained with three commonly used methods, mTEC (Becton Dickinson, Sparks, MD), m-ColiBlue (Hach, Loveland, CO), and Colilert-18/IDEXX Quanti-Tray 2000 (IDEXX, Westbrook, ME). Blue colonies on Petrifilm plates were most reliably identified as E. coli when accompanied by gas formation, as determined by characterization of the colonies on MacConkey agar plates (PML Microbiologicals, Mississauga, ON, Canada) and by polymerase chair reaction (PCR) with E. coli-specific primers. The main disadvantage of Petrifilm plates for environmental water testing is the small volume (1 mL per sample) that can be tested; however, the plates appear to be suitable for screening and locating sites that exceed criteria for total body and partial body contact. Simplicity of use and storage, reliability, and relatively low cost make Petrifilm plates suitable for volunteer-based and educational water quality monitoring applications, particularly when used as a preliminary screening method to identify problem sites.

DNA, Bacterial↗