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Biomedical subjects

G Tobin

Publications and source records attributed to G Tobin.

At least 73 records · Page 4Linked to original sources
PubMed1989

Receptors involved in the nervous system regulation of polyamine metabolism in rat salivary glands.

Polyamines are important for protein synthesis and tissue growth. In rat salivary glands, the activity of ornithine decarboxylase (ODC), the enzyme catalysing the formation of putrescine, and the content of putrescine, spermidine, spermine and N1-acetylspermidine were assayed after parasympathetic or sympathetic nerve stimulation in the presence of various autonomic receptor blockers. Increases in ODC activity occurred on activation of non-adrenergic and non-cholinergic receptors in response to parasympathetic nerve stimulation and on activation of alpha(alpha 1)- as well as of beta(beta 1)-adrenoceptors in response to sympathetic nerve stimulation. Moreover, in parotid glands, a beta(beta 1)-adrenoceptor-mediated inverse pathway for putrescine formation seemed to exist: from spermidine via N1-acetylspermidine.

Animals↗
PubMed1989

Secretion of protein from salivary glands in the ferret in response to vasoactive intestinal peptide.

1. Secretory responses of ferret parotid and submandibular glands were investigated in the presence of muscarinic, alpha- and beta-adrenoceptor blocking agents. 2. In pentobarbitone-anaesthetized animals I.V. doses of vasoactive intestinal peptide (VIP) failed to elicit overt secretion of saliva from either gland. 3. However, an occult secretion of protein occurred in response to VIP from both types of gland. This was revealed by means of a subsequent I.V. wash-out injection of substance P, which is a potent secretagogue in ferrets. This effect of VIP was much more marked in the submandibular than in the parotid gland. 4. Electrical stimulation of the chorda-lingual nerve gave rise to protein secretion in the submandibular gland at subthreshold frequencies for overt non-cholinergic, non-adrenergic secretion of saliva, as revealed by subsequent wash-out I.V. injection of substance P. 5. Protein secretion in response to VIP was also demonstrated in vitro by perifusing small pieces of the two glands. The sensitivity of submandibular tissue to VIP greatly exceeded that of the parotid tissue. 6. It is concluded that VIP, or a structurally related peptide, may be involved in the non-cholinergic, non-adrenergic secretory response of ferret salivary glands evoked by parasympathetic nerve stimulation.

Animals↗
PubMed1988

Hydroxylapatite (H/A) particulate versus cones as post-extraction implants in humans. Parts I & II.

Hydroxylapatite was evaluated in two separate parallel studies in humans as ridge maintenance implant materials. The techniques for the use of each, the methods of analyzing them and the postoperative results were reported and compared. Particulate H/A (20 mesh) served more reliably and predictably than the same material in cone form, when used in alveoli after dental extractions as an immediate grafting material for ridge maintenance in humans.

Adult↗
PubMed1988

Voluntary food intake of lean and obese Zucker rats in relation to dietary energy and nitrogen content.

Genetically obese (fa/fa) Zucker rats maintain a normal lean body size but deposit excessive amounts of body fat. Preferential use of substrates for lipid synthesis results in inefficient use of dietary nitrogen for protein deposition. Three studies were carried out to determine whether an increased protein requirement caused hyperphagia and whether young Zucker rats preferentially regulated protein or energy intake. Rats were offered isoenergetic diets with nitrogen contents ranging from 4.5 to 53.2 mg/g, or isonitrogenous diets with energy contents of 2.2, 3.3 or 4.2 kcal/g. In both situations obese rats had significantly higher food intakes than lean rats. Within phenotype the rats maintained an almost constant energy intake so that nitrogen intake was proportional to dietary nitrogen concentration. In a third experiment lean and obese rats were given different proportions of their control protein intake by stomach tube. Energy intake was determined by voluntary consumption of a protein-free diet. Within phenotype energy intake was the same for all levels of protein intake. It appears that obese Zucker rats regulate energy intake at an elevated level and that protein intake is determined by dietary nitrogen content. Hyperphagia does not appear to result from a desire to obtain protein.

Animals↗
PubMed1988

Tachykinin involvement in parasympathetic nerve-evoked salivation of the ferret.

1. The tachykinin antagonist (D-Arg1, D-Cl2Phe5, Asn6, D-Trp7.9, Nle11)-substance P, injected intravenously, blocked salivary secretion from the ferret parotid and submandibular glands in response to subsequent i.v. injections of the tachykinins, substance P and neurokinin A. 2. The tachykinin antagonist reduced the parasympathetic nerve-evoked secretion of parotid and submandibular saliva by 15-20% and 35-40%, respectively. Atropine abolished the remaining secretory response. 3. The 'atropine-resistant' parasympathetic nerve-evoked secretion of saliva from the parotid and submandibular glands (about 5 and 30%, respectively, of that before administration of atropine) was abolished by the tachykinin antagonist. 4. The tachykinin antagonist was without effect on the protein concentration of parotid and submandibular saliva secreted in response to parasympathetic nerve stimulation. Parotid and submandibular saliva lacked amylase. 5. Atropine reduced the protein concentration of the submandibular saliva secreted in response to parasympathetic nerve stimulation by 50%; this was the protein concentration of substance P-evoked saliva. 6. The secretory response to methacholine and to stimulation of preganglionic sympathetic nerve fibres, tested in rats, was unaffected by the tachykinin antagonist, contra-indicating an unspecific action of the antagonist. 7. The results suggest that the neuronal release of tachykinins is probably important in the nerve-evoked secretory response of the parotid and submandibular glands.

Amylases↗
PubMed1988

Non-adrenergic, non-cholinergic salivary secretion in the ferret.

Secretion of parotid and submandibular saliva evoked by electrical stimulation of the parasympathetic nerves occurred in the presence of adrenergic and cholinergic blocking agents. The 'atropine-resistant' response amounted to about 30% in the submandibular gland and to about 5% in the parotid gland as compared to the response before administration of antimuscarinic agents. The 'atropine-resistant' secretion was found at relatively high frequencies, and the latency between the start of the stimulation and the onset of secretion was long. Upon long-lasting stimulation the 'atropine-resistant' secretion decreased rapidly and markedly. The tachykinins substance P (SP) and substance K, injected I.V., evoked flow of saliva from both glands. Given singly, exogenous vasoactive intestinal peptide (VIP) caused no salivary flow. However, it enhanced the tachykinin-evoked secretory response. The response to SP was also enhanced when I.V. injections of this peptide were combined with nerve stimulation, even at subthreshold frequencies for secretion, in the presence of the autonomic receptor blockers. Both tachykinins and VIP are putative transmitters involved in mediating the 'atropine-resistant' secretory response.

Animals↗
PubMed1988

The effects of atropine and chronic sympathectomy on maximal parasympathetic stimulation of parotid saliva in rats.

1. The effects of stimulating the postganglionic parasympathetic nerve to the parotid gland, the auriculo-temporal nerve, continuously at 40 Hz for 80 min have been assessed on the flow of saliva and its amylase content during each 10 min period and on the glandular morphology at the end of the stimulation, in female Sprague-Dawley rats under chloralose anaesthesia. Adrenergic responses were blocked by prior administration of dihydroergotamine (1 mg/kg I.P.) and propranolol (1 mg/kg I.P.). The contralateral unstimulated parotid gland from each animal was used for morphological control purposes. 2. In normal animals there was a copious flow of saliva reaching 3 ml or more in 80 min. It was well maintained after a gradual small decline and the flow in the last 10 min period was still 60% of that in the initial period. Amylase output was relatively high in the initial period but then declined more rapidly than the flow. The acini were densely packed with granules on the control side and showed a moderate amount of degranulation on the parasympathetically stimulated side. 3. After atropine (2 mg/kg I.V.), normal animals initially showed a moderate flow of saliva, being 41% of the non-atropinized animals, but there was a rapid decline and the total flow over 80 min was only 15% of that in the non-atropinized animals. The amylase secreted was also high initially and showed a rapid decline; the total amount secreted was similar to that in non-atropinized animals. The morphology was similar to that in non-atropinized animals and showed a similar loss of acinar granules on the stimulated side. 4. Chronic bilateral postganglionic sympathectomy (4-6 weeks duration) caused a drastic reduction in the capacity of the gland to secrete saliva in response to parasympathetic stimulation, reaching only one-third of that from normal animals. The initial output of amylase was greater than in normal animals but the total output was similar. The control unstimulated sympathectomized glands appeared similar morphologically to normal resting glands. However, on the parasympathetically stimulated side, besides the usual amount of acinar degranulation, there was also a conspicuous development of acinar vacuolation, not seen in the other groups of animals.(ABSTRACT TRUNCATED AT 400 WORDS)

Amylases↗
PubMed1987

Toxic shock syndrome following breast and nasal surgery.

Toxic shock syndrome is a rapidly developing disease which may be lethal if not recognized and treated early. While this disease is usually associated with menstruating females, it is being seen in both male and female patients following clean, elective surgery. Toxic shock syndrome has been reported following surgical procedures which normally have a very low incidence of postoperative wound infections. Toxic shock syndrome is associated with Staphylococcus aureus bacteria which produce the toxic shock syndrome toxin 1. Three patients with postoperative toxic shock syndrome, of varying degrees of severity, are presented. Prompt institution of resuscitative and therapeutic measures can prevent the potentially fatal outcome of this postoperative complication.

Adult↗
PubMed1987

Substance K and salivary secretion in the rat.

Intravenous injections of substance K (SK), a novel member of the family of tachykinins, evoked secretion from the three major salivary glands of the rat in the presence of muscarinic, alpha-adrenergic and beta-adrenergic receptor blockade; the submaxillary glands contributed most and the sublingual glands least to the total volume secreted. SK was less potent than substance P (SP) in evoking fluid and amylase secretion. However, the amylase concentration in parotid saliva evoked by SK was twice that evoked by SP, a finding which indicates that in the glands there are more than just one type of tachykinin receptors. Vasoactive intestinal peptide enhanced the SK evoked fluid response and increased the amylase concentration in parotid saliva. SK is a possible transmitter involved in the atropine-resistant parasympathetic nerve evoked salivation in the rat.

Amylases↗
PubMed1987

Non-adrenergic, non-cholinergic parasympathetic secretion in the rat submaxillary and sublingual glands.

Atropine resistant secretion from the submaxillary and sublingual glands was demonstrated upon electrical stimulation of the chorda-lingual nerve at high frequencies. The flow rate of the protein-rich saliva was low, and it declined rapidly and markedly upon prolonged stimulation. The results show that one or more substances other than acetylcholine are released by parasympathetic stimulation and that they may be of importance for the regulation of the exocrine functions of the glands. When the continuous mode of electrical stimulation at a low frequency of the nerve was changed to an intermittent mode of stimulation at a high frequency (in the absence of atropine), the secretion of fluid and protein decreased.

Animals↗
PubMed1987

Body composition of lean and obese Zucker rats in parabiosis.

Parabiosis is the surgical union of two animals to produce a chronic blood exchange. This model has previously been used to demonstrate the involvement of a blood-borne factor in the feedback control of food intake and regulation of energy balance. It has been hypothesized that obese rats produce a humoral agent that acts centrally to inhibit food intake and accumulation of fat. In this study 50-day-old male or female Zucker rats were joined in either lean-lean pairs or lean-obese pairs. They ate ad libitum until 152 days of age when body composition was determined. Parabiosis inhibited growth in all rats compared with single controls. Lean partners of obese rats had reduced carcass weights, the same percent body protein but less fat than members of lean-lean pairs. Female rats showed larger changes in body composition than did males. These results suggest that obese Zucker rats produce the hypothesized regulatory signal but do not respond to it.

Animals↗
PubMed1985

Natural history and prognosis of unstable angina.

One hundred patients admitted to coronary care with unstable angina were followed for a period of 1 year. A conservative approach to treatment was adopted. Routine beta blockers, calcium antagonists, and anticoagulants were not employed. Patients with persistent pain following admission were treated with nitrates only and with symptomatic treatment. One death and nine nonfatal infarctions occurred within the first 28 days after admission. A total of eight deaths, 14 nonfatal infarctions, and three readmissions for unstable angina occurred during the follow-up period of 1 year. Of the various initial factors studied, persistence of pain and the magnitude and extent of ECG ST-T changes were the only predictors of an unfavorable outcome. Non-smokers and those with a previous history of angina on effort had a significantly higher incidence of persistence of pain. The withdrawal of beta blockers on admission and the late administration of beta blockers to those with persistent pain did not appear to influence outcome.

Adrenergic beta-Antagonists↗
PubMed1985

Increased polyamine formation in rat salivary glands by stimulation of their autonomic nerve supply.

Ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis, was measured in the three major salivary glands of rats and mice. Enzyme activity and glandular putrescine content increased after continuous stimulation of the parasympathetic or sympathetic salivary nerves for 3 h. The activity was markedly reduced in animals fasted for 24 h to decrease nervous-reflex activation of the glands. Thus ODC activity may be linked with synthesis of secretory macromolecules.

Animals↗
PubMed1985

Depletion of neuropeptides in rat parotid glands and declining atropine-resistant salivary secretion upon continuous parasympathetic nerve stimulation.

In rats the parasympathetic auriculo-temporal nerve on one side was continuously stimulated at 40 Hz for 20-80 min in the presence of adrenergic blockers (dihydroergotamine and propranolol) +/- atropine. During the first 10 min this gave rise to a flow of saliva from the parotid gland that in the atropinized rats amounted to 35% of that found in rats not treated with atropine, while the protein and amylase outputs were 75% of those in non-atropinized rats. The atropine-resistant secretion of fluid and proteins declined to 5-10% of the initial value within 40 min but did not cease completely even after 80 min. The marked reduction in secretory responses was not due to desensitization or exhaustion of the gland cells. The nerve stimulation reduced the parotid gland content of vasoactive intestinal peptide (VIP) and substance P (SP) to approximately 60 and 25% of that of contralateral glands after 20 and 60 min, respectively. The probable explanation for the decline in secretory response seems to be depletion of non-adrenergic, non-cholinergic transmitter(s). The present results suggest that neuropeptides are involved in the regulation of salivary secretion but provide no direct evidence that either VIP or SP is responsible for the atropine-resistant salivary secretion.

Amylases↗
PubMed1984

Effects of atropine or high frequency burst excitation on the composition of parasympathetic rat parotid saliva.

In the presence of atropine continuous trains of impulses applied to the auriculo-temporal nerve at relatively high frequencies evoked a flow of parotid saliva that amounted to 5-10% of that before administration of the muscarinic blocker. The output of total protein, amylase, sodium and potassium decreased markedly. However, in terms of concentration protein and amylase increased, while sodium decreased and potassium was unchanged. When, in the absence of atropine, the continuous mode of stimulation was replaced by bursts of impulses of high frequencies the amount of saliva decreased. However, the concentration of protein, amylase and potassium increased, while the concentration of sodium decreased. The findings are discussed in relation to a possible peptidergic innervation of the secretory elements.

Amylases↗
PubMed1984

The relationship between energy expenditure and environmental temperature in congenitally obese and non-obese Zucker rats.

The energy expenditure of normal and congenitally obese adult female Zucker rats has been measured by continuous indirect calorimetry for periods of 3-10 days at ambient temperatures varied from 30 to 5 degrees C. Rectal temperatures were also recorded. Exposure to cold caused no ill-effects in normal or obese rats. The rectal temperatures of obese rats were about 1 degree C lower than those of normal rats. The rectal temperatures of normal rats did not change measurably with ambient temperature; in obese rats rectal temperature rose slightly as ambient temperature fell. In normal and obese rats, energy expenditure showed a smooth, steeply sloping, negative relationship to ambient temperature. Energy expenditure per rat was higher in obese than in normal rats at all temperatures. The two slightly curvilinear regressions were nearly 'parallel', with a separation of about 40 kJ/day per rat at the mid-point. This study therefore does not confirm suggestions that obese Zucker rats suffer from a defect in the level of energy expenditure, or in their capacity to increase it when exposed to cold. It is suggested that in both normal and obese rats the level of energy expenditure was determined by thermoregulatory control. The greater heat production of obese rats may have been a response to their lower core temperature. A steady state in which greater heat production is associated with lower core temperature implies lower insulation between body core and surface. This could be due to greater blood flow.

Animals↗
PubMed1983

Relative secretory contributions of the three major salivary glands of the rat in response to substance P and super-sensitivity.

In vivo salivation in the rat in response to a range of intravenous doses of substance P was studied. The ducts of the parotid, submandibular and sublingual glands were cannulated. The secretory threshold dose of substance P, in microgram/kg, was 0.05-0.1 in the submandibular glands, 0.2 in the parotid glands and 0.2-0.5 in the sublingual glands. The maximal secretory response in all three types of glands was obtained at a dose level of 5-10 micrograms/kg. The total amount of saliva secreted at this dose level from the three pairs of glands was calculated to about 300 mg; the submandibular glands were responsible for 65 per cent, the parotid glands for 32 per cent and the sublingual glands for 3 per cent. Parasympathetic decentralization but not sympathetic denervation caused the sublingual glands to develop a super-sensitivity to substance P. The secretory effect of substance P was not exerted via cholinergic, alpha-adrenergic or beta-adrenergic receptors.

Animals↗