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Biomedical subjects

G W Bennett

Publications and source records attributed to G W Bennett.

At least 55 records · Page 3Linked to original sources
PubMed1990

5-Hydroxytryptamine, substance P, and thyrotropin-releasing hormone in the adult cat spinal cord segment L7: immunohistochemical and chemical studies.

The terminal projections of the descending 5-hydroxytryptamine (5-HT) bulbospinal pathway and the coexistence among 5-HT-, substance P (SP)-, and thyrotropin-releasing hormone (TRH)-like immunoreactivities (LI) in fibers innervating the L7 segment in the cat spinal cord were studied quantitatively and semiquantitatively by use of the indirect double-staining immunofluorescence technique. The content of 5-HT, SP, and TRH in different parts of the spinal cord was determined by use of radioimmunoassay (RIA) (SP and TRH) and high-performance liquid chromatography with electrochemical detection (HPLC-ECD) (5-HT). For all three substances studied, immunoreactive (IR) axon terminals were found in all parts of the gray matter, but with clear regional variation in the density of innervation. Thus, all three substances showed a dense innervation in the motor nucleus, particularly in the ventral part of the nucleus, while the superficial dorsal horn was very densely innervated by SP-IR fibers (laminae I and II) and TRH-IR fibers (laminae II and III). In the motor nucleus, the studied substances coexisted to a very high degree, but some 5-HT-IR fibers (about 10%) lacked peptide-LI and some SP-IR fibers (about 10%) lacked 5-HT-LI while virtually all TRH-IR fibers also contained 5-HT-LI. In the superficial dorsal horn (laminae I-III), no coexistence was detected, while other parts of the gray matter displayed various degrees of coexistence in between those found in the motor nucleus and laminae I-III. The quantitative analysis of IR varicosities in the motor nucleus suggested that the unilateral L7 motor nucleus is innervated by about 55-110 x 10(6) 5-HT-IR nerve terminals, which may indicate as many as 4,000 boutons per descending 5-HT cell body in the brain stem only with this restricted projection. When combing these results with the biochemical data, it could be calculated that the concentration of 5-HT in IR varicosities is about 3-6 x 10(-3) M, while the corresponding figures for SP and TRH was 0.3-0.5 x 10(-3) M and 0.1-0.2 x 10(-3) M, respectively. In cats subjected to spinal cord transection at the lower thoracic level, all 5-HT-IR fibers in the L7 segment had disappeared 44 days after the lesion, indicating a strict suprasegmental origin of 5-HT-IR fibers in this segment.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Influence of insecticide treatment on German cockroach (Dictyoptera: Blattellidae) movement and dispersal within apartments.

Two similar studies were done to investigate effects of insecticide treatments on German cockroach, Blattella germanica (L.), movement and dispersal within individual units in multifamily housing. In the first study, Whitmire PT-565 Pyrethrum Insect Fogger (pyrethrins), Diazinon 4E (diazinon), Protector (permethrin), and Baygon 1.5 (propoxur) did not induce any significant changes in cockroach distribution, and rates of movement within apartments decreased. In the second study, populations treated with sublethal doses of pyrethrins and resmethrin settled to their original distribution 24 h after treatment. Results from both studies indicate that thorough insecticide applications do not significantly affect German cockroach population dispersal or movement patterns within apartments.

Animals↗
PubMed1990

Topical and oral toxicity of sulfluramid, a delayed-action insecticide, against the German cockroach (Dictyoptera: Blattellidae).

The LD50 of sulfluramid topically applied to 2-d-old, fifth instars of the German cockroach, Blattella germanica (L.), was estimated at 14.5 micrograms/g (95% FL = 13.7-15.4 micrograms/g). Sulfluramid was significantly more toxic than topically applied hydramethylnon (LD50 = 29.2 [19.0-46.5] micrograms/g). Sulfluramid had delayed toxicity but caused mortality significantly faster than hydramethylnon after topical application. The oral LD50 against newly enclosed, fifth instars was estimated to be 4.1 (3.9-4.4) micrograms/g; this toxicity was significantly greater than when sulfluramid was topically applied. Mortality caused by sulfluramid occurred significantly more slowly in the dietary exposures than in the topical applications. Sulfluramid at 1,000 ppm in diets was not a feeding deterrent to nymphal B. germanica.

Animals↗
PubMed1990

Influence of fenoxycarb on German cockroach (Dictyoptera: Blattellidae) populations in public housing.

In a study examining three application rates for fenoxycarb, new interpretations of population age structure in relation to sterility levels and population reductions were used to establish important concepts in the management of German cockroaches, Blattella germanica (L.), with juvenoids. No significant differences in population reductions were noted when 0.5%, 0.25%, or 0.125% fenoxycarb was used to supplement propetamphos. However, significant differences in levels of induced sterility and in the age structure (measured as nymph-to-adult ratios) of treated populations were detected. The 0.125% rate caused lower, less consistent levels of sterility than the two higher rates, which maintained approximately 80% sterility from 4.5 mo and beyond. In addition, the 0.125% rate did not significantly reduce nymph-to-adult ratios in treated populations relative to that caused by the propetamphos alone (positive control). The two higher rates significantly reduced nymph-to-adult ratios, thereby lowering biotic potential and the capacity of a population to rebound from suppression. A relationship between the level of sterility induced by juvenoids and reductions in nymph-to-adult ratios permitted formulation of a biological action threshold for regulating treatment. This action threshold appears to be more meaningful than time intervals for scheduling retreatments in the long-term management of German cockroaches with juvenoids.

Age Factors↗
PubMed1990

Residual effectiveness of insecticides for control of German cockroaches (Dictyoptera: Blattellidae) in food-handling establishments.

Residual effectiveness of insecticides was compared for two treatment methods at various sites within two commercial kitchens. For all sites and insecticides, German cockroach, Blattella germanica (L.), mortality was greatest for treatments of cracks and crevices than for treatments of exposed surfaces. Mortality at the dishwashing site was lower than at all other sites. We attributed reduced mortality at the dishwashing site to a higher vapor pressure deficit. Mortality and the amount of insecticide residue recovered from treated surfaces were closely correlated. These data demonstrate that careful placement of residual insecticide treatments will influence their effective longevity.

Animals↗
PubMed1990

Distribution and movement patterns of German cockroaches (Dictyoptera: Blattellidae) within apartment buildings.

Trapping experiments conducted in multifamily apartments indicated movement of German cockroaches, Blattella germanica (L.), between apartments was greatest in adjacent kitchens; 65% of the emigrating cockroaches came from adjoining kitchen areas. Cockroach distribution parameters indicated that all life stages were aggregated. Aggregation was most pronounced for small nymphs, followed by adults; large nymphs were the least aggregated. Iwao's regression coefficients and resultant distributions implied movement of large nymphs was greatest, followed by adults and small nymphs.

Animals↗
PubMed1990

Ovicidal activity of chitin synthesis inhibitors when fed to adult German cockroaches (Dictyoptera: Blattellidae).

Ovicidal activity was observed in four adult groups (virgin males; virgin females; newly gravid females; and inseminated, reproducing females) of the German cockroach, Blattella germanica (L.), fed the chitin synthesis inhibitors triflumuron, chlorfluazuron, hexafluron, and UC 84572 (structure not disclosed) at the LC50's and LC95's determined from fifth-stage nymphs. All compounds were active only when fed to reproducing females (including the feeding period in which the ootheca is developing). Hexafluron and triflumuron at the LC50 caused 100% inhibition of hatch in reproducing females. Chlorfluazuron and UC 84572 at the LC50 had similar ovicidal activity (45.8 and 50.0% hatch, respectively). Female German cockroaches fed the chitin synthesis inhibitors before mating and after the ootheca had protruded from the abdomen were not affected. Reproductive capabilities of males were not affected, and males did not effectively transfer the compounds to untreated females during mating.

Animals↗
PubMed1990

Comparative sterilizing and ovicidal activity of fenoxycarb and hydroprene in adults and oothecae of the German cockroach (Dictyoptera: Blattellidae).

Adults and oothecae of the German cockroach, Blattella germanica (L.), were treated topically with the juvenoids fenoxycarb and hydroprene. Fenoxycarb suppressed reproduction when applied at 10 micrograms/microliters to virgin and fertilized females. Production of offspring also was reduced when males treated with 10 micrograms/microliters of fenoxycarb were mated with untreated females. Fenoxycarb (10 micrograms/microliters) also exhibited ovicidal activity, particularly when applied to 4-d-old oothecae. Ovicidal activity by fenoxycarb diminished when applied to oothecae older than 8 d. No reproductive or ovicidal effects were caused by 1 or 10 micrograms/microliters of hydroprene.

Animals↗
PubMed1989

Comparative behavioural and biochemical effects of repeated intrathecal administration of thyrotrophin-releasing hormone (TRH) or two analogues of TRH in adult rats.

The effect of repeated intrathecal injection of thyrotrophin-releasing hormone (TRH) and two analogues of TRH, C-terminally modified RX 77638 and N-terminally modified CG 3509, were examined on behavioural (wet-dog shakes and forepaw licking) and biochemical markers for spinal motoneurones, bulbospinal raphe nerve terminals and the pituitary-thyroid axis in rats. Saline (10 microliters washed in with 15 microliters), TRH (20 micrograms), RX 77368 (2 micrograms) or CG 3509 (2 micrograms) were administered intrathecally (twice daily for 3 or 5 days), after which levels of plasma-free thyroxine and thyroid-stimulating hormone (TSH) were measured and the dorsal and ventral portions of the thoracolumbar spinal cord, brainstem and hypothalamus were assayed for TRH- and calcitonin gene-related peptide (CGRP)-like immunoreactivity, levels of indoleamines and the activity of choline acetyltransferase (ChAT). Behavioural tolerance developed rapidly with consecutive injections of RX 77368, such that wet-dog shakes were significantly reduced and forepaw-licking tended to be decreased by the third intrathecal injection. Five, but not 3, days of administration of RX 77368 selectively elevated levels of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid in the ventral spinal cord, where these substances are principally located in bulbospinal raphe nerve terminals. The time course of the change in indoleamines suggests that administration of TRH peptides elevated the synthesis, rather than the release, of 5-HT from these nerve terminals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

A comparison of the motor behaviours produced by the intrathecal administration of thyrotrophin-releasing hormone and thyrotrophin-releasing hormone analogues in the conscious rat.

The behaviours evoked by the intrathecal injection of thyrotrophin-releasing hormone and a variety of analogues (RX77368, CG3509 and CG3703) were examined in conscious rats and the spread of injectate at the peak of the behavioural response was determined using 14C-labelled RX77368. The number of wet-dog shakes observed following intrathecal injection of thyrotrophin-releasing hormone, RX77368, CG3509 and CG3703 was linearly related to log10 dose (0.01-200 micrograms) in the first 6 min with the relative potencies being 1:7:10:60 respectively. The thyrotrophin-releasing hormone analogues also produced a marked forepaw-licking behaviour, but this did not increase with dose. Intrathecal or intraperitoneal pretreatment with prazosin (0.5 microgram and 1 or 2 mg/kg, respectively) attenuated both the wet-dog shake and forepaw-licking behaviours normally produced by the thyrotrophin-releasing hormone peptides. Following intrathecal [14C]RX77368 the radioactivity was principally restricted to the spinal cord with only limited amounts rostral to the rhombencephalon. These results imply that a tonically active bulbospinal noradrenergic pathway facilitates both thyrotrophin-releasing hormone-induced behaviours via alpha 1-adrenoceptors.

Animals↗
PubMed1989

Comparative activity of fenoxycarb and hydroprene in sterilizing the German cockroach (Dictyoptera: Blattellidae).

Last-instar German cockroaches, Blattella germanica (L.), were treated topically with the juvenoids, fenoxycarb and hydroprene, and observed for reproductive capabilities during adulthood. Hydroprene had a significantly lower SD50 (dose required to sterilize 50% of the cockroaches) for males (39.82 micrograms/g body weight) compared with females (86.64 micrograms/g body weight). In contrast, SD50's of fenoxycarb did not differ significantly between the sexes (18.04 and 13.66 micrograms/g body weight for females and males) and were significantly lower when compared with SD50's of hydroprene. A strong positive relationship between wing twisting (a morphogenetic effect caused by juvenoids) and sterility was observed among cockroaches treated with 100 and 10 micrograms/microliters of each juvenoid. However, only 16% of females displaying twisted wings were sterile when treated with 1 microgram/microliter of hydroprene. Cockroaches treated with 100 micrograms/microliters of hydroprene lived 10-14 wk fewer than control adults and often attempted a sixth (supernumerary) molt.

Animals↗
PubMed1989

Efficacy of chitin synthesis inhibitors on nymphal German cockroaches (Dictyoptera: Blattellidae).

Second- and fifth-instar Blattella germanica (L.), fed the chitin synthesis inhibitors triflumuron, chlorfluazuron, hexafluron, and UC 84572 (structure not disclosed) were examined for mortality and developmental abnormalities. All compounds were active against B. germanica (L.), with lower diet concentrations being required to kill second instars compared with fifth instars. Chlorfluazuron was significantly more active against second and fifth instars (LC50 = 0.000191 and 0.000363% AI, respectively for the second and fifth instars). UC 84572 also killed nymphs at extremely low concentrations (LC50 = 0.000508 and 0.000754% AI, respectively, for second and fifth instars). LC50's for hexafluron and triflumuron against fifth instars were more than 1,000 times higher than that for chlorfluazuron. Sensitive periods of exposure were determined by comparing effects when four different age classes of fifth instars (1-, 4-, 7-, and 10-d old) fed on the compounds for 3 d. Triflumuron was most effective when ingested during the first three age classes and hexafluron was most effective during the last three age classes. Chlorfluazuron and UC 84572 were most effective when ingested during the second age class (days 4-6). Adults surviving exposure during the fifth instar were often deformed and weak; they died at a greater rate than the controls. However, most surviving adults were able to reproduce normally.

Animals↗
PubMed1989

Involvement of 5-HT2 receptors in the behaviours produced by intrathecal administration of selected 5-HT agonists and the TRH analogue (CG 3509) to rats.

1. The behavioural effects of the intrathecal injection of a thyrotrophin-releasing hormone (TRH) analogue L-orotyl-L-histidyl-prolineamide (CG 3509, 0.5 micrograms), the non-selective 5-HT1 and 5-HT2 receptor agonist 5-methoxy-N,N'-dimethyltryptamine (5-MeODMT, 2-100 micrograms) and the selective 5-HT2 receptor agonist 2,5-dimethoxy-alpha,4-dimethyl-benzene ethamine hydrochloride (DOM, 2-25 micrograms) were compared with the response of systemically administered 5-MeODMT (2 mg kg-1, i.p.) in rats, to establish whether the agonist-induced behaviours were mediated by bulbospinal 5-HT1 or 5-HT2 receptors. 2. Intrathecal injection of 5-MeODMT or DOM produced dose-related back muscle contractions (a previously undocumented behaviour) and wet-dog shakes which were both markedly attenuated by ritanserin pretreatment (1 mg kg-1, i.p.) indicating the involvement of 5-HT2 receptors. In contrast, reciprocal forepaw treading, flat body posture and Straub-tail were evoked by 5-MeODMT but not by DOM indicating that these behaviours were not produced by 5-HT2 receptor activation alone. However, as ritanserin pretreatment reduced the reciprocal forepaw treading induced by intrathecal 5-MeODMT, this behaviour may be facilitated by 5-HT2 receptor activation. 3. Intrathecal 5,7-dihydroxytryptamine (5,7-DHT, 2 x 150 micrograms) treatment decreased thoraco-lumbar spinal cord 5-HT (-95%) and potentiated the back muscle contractions produced by intrathecal DOM injection without altering the wet-dog shake behaviour. None of the components of the 5-HT syndrome produced by 5-MeODMT (2 mg kg-1, i.p.), with the exception of a small increase in wet-dog shakes, was significantly altered by intrathecal 5,7-DHT (which reduced thoraco-lumbar spinal cord 5-HT by 84%). Taken together these data suggest that the only 5-HT agonist-induced behaviour mediated by the activation of 5-HT2 receptors located postsynaptic to bulbospinal 5-hydroxytryptaminergic (5-HTergic) neurones was back muscle contractions. 4. The wet-dog shake and forepaw licking behaviors produced by intrathecal CG 3509 (0.5 micrograms) were attenuated when ritanserin was administered intrathecally 30 min before, but not when it was given at the same time as CG 3509 and neither behaviour was altered by intrathecal 5,7-DHT. This suggests that bulbospinal 5-HTergic neurones are not involved in the production of these TRH analogue-induced behaviours and that the 5-HT2 receptors which mediate these behaviours are not located in the spinal cord.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMed1989

Effect of chronic intra-accumbens administration of the TRH analogue CG3509 on histamine-induced behaviour in the rat.

1. The present study has investigated the effect of chronic intra-accumbens administration of the thyrotrophin-releasing hormone (TRH) analogue, CG3509, on CG3509- and histamine-induced spontaneous motor activity and brain TRH-like immunoreactive (TRH-LI) levels in the rat. 2. Chronic intra-accumbens administration of CG3509 (5 x 5 micrograms over 3 days) induced: (a) a significant (P less than 0.05) reduction in intra-accumbens CG3509 (0.5 micrograms)-induced hyperactivity, (b) reduced levels of TRH-LI in the nucleus accumbens but not other brain regions, (c) a marked increase (107%, P less than 0.01) in histamine-induced non-locomotor hyperactivity. 3. The present results demonstrate that alteration of central TRH function following treatment with a TRH analogue enhances the effect of intra-accumbens histamine on behavioural hyperactivity, possibly via changes in H1 receptors and suggest that the neuropeptide, TRH and histamine interact in behavioural arousal mechanisms in rat brain.

Animals↗