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At least 253 records · Page 14Linked to original sources
PubMed1994

Physiological characteristics of periodontal mechanosensitive neurones in the inferior alveolar nerve of the cat.

Unitary discharges of periodontal mechanosensitive (PM) fibres were recorded from cat inferior alveolar nerve. More than half (66%) of the PM units were single-tooth ones sensitive to only one tooth. The majority (78%) responded sustainedly to stimulation of the mandibular canine tooth. The multitooth units responded predominantly to stimulation of the canine and incisor teeth. A broad-type response field, with a directional range of 180-360 degrees for the response angle, was most frequent. The optimal stimulus direction was oriented in the caudomedial or caudolateral direction. Most (93%) of the single-tooth and multitooth PM units were fired at relatively regular spike intervals by tooth stimulation. In the multitooth units, conditioning and test stimuli were applied to a pair of teeth in the receptive field in order to examine the mechanical spread effect of the conditioning stimulus on the adjacent tooth. The conditioning stimulus was given in the optimal stimulus direction and the test stimulus in the direction opposite to that direction. All multitooth units of the regular spike-interval type had only one tooth ('firing-stopped' tooth) in their receptive fields, the test stimulus to which stopped the discharges evoked by the conditioning stimuli to other teeth. The firing-stopped tooth, however, was rare in multitooth units of the irregular spike interval type.

Animals↗
PubMed1990

Physiological characteristics of responses of wide dynamic range spinal neurones to cutaneously applied vibration in the cat.

Extracellular single-unit recordings were made from wide dynamic range neurones in the lumbar dorsal horn of anaesthetized or decerebrated cats. Vibration applied to the skin at a frequency of 80 Hz could evoke 3 distinct types of response--excitation, depression or a biphasic response consisting of excitation followed by depression. By applying vibration at different sites, a given neurone was found to show more than one type of response. Parametric studies of the depressant and biphasic responses were made because previous studies indicated that adenosine mediates the depression in these types of response. Thus, amplitude- and frequency-response relationships were determined at individual stimulation sites: amplitude was varied from 0.001 to 1.0 mm (frequency, 80 Hz) and the frequencies studied were 10, 20, 40, 80, 120 and 240 Hz (amplitude, 0.15 mm). Vibration at amplitudes greater than 0.15 mm caused a decrease in the rate of discharge during the period of stimulation, the magnitude of this decrease varying directly with amplitude; at amplitudes of 0.15 mm and less vibration had no statistically significant effect. With regard to the frequency-response relationship, a decrease in discharge rate occurred at frequencies of 120 and 240 Hz, with the more pronounced effect at 240 Hz; excitation occurred at 40 Hz and there was no statistically significant effect at other frequencies. Amplitude- and frequency-response relationships for the depressant and the biphasic responses were analyzed separately. In the case of depressant responses, the magnitude was monotonically related to the amplitude of stimulation and depression occurred only at frequencies of 80 Hz or greater, with higher frequencies being more effective. The biphasic responses appeared to consist of 2 subtypes termed biphasic-1 and biphasic-2 responses. For biphasic-1 responses, the amplitude- and frequency-response curves were similar to those of depressant responses. Biphasic-2 responses differed in that the response was biphasic when the stimulation frequency was 80 Hz or greater and the amplitude was 0.3 mm or more, yet, at lower frequencies and/or amplitudes vibration evoked excitation. The similarities in the amplitude- and frequency-response relationships of depressant and biphasic-1 responses raise the possibility that these responses might be mediated by a single class of primary afferent. Both depressant and biphasic responses were evoked when stimulation parameters (2 microns, 240 Hz) were used which selectively activate Pacinian corpuscle afferents. Depression with 240-Hz stimulation was attenuated by administration of caffeine (60 mg/kg i.v.) suggesting that the depressant and biphasic-1 responses may be mediated by afferents from Pacinian corpuscles.

Action Potentials↗
PubMed1993

Alterations in noradrenergic physiological characteristics with DOCA-hypertension: interaction between norepinephrine and GABA in rat lateral hypothalamus.

The lateral hypothalamus (LH) is involved in the central integration of fluid and electrolyte balance. Several studies have suggested a role for norepinephrine (NE) in these functions. In previous studies we presented evidence in support of a modulatory role for NE within the LH circuitry. Specifically, NE facilitated responses of LH cells to synaptic inputs and putative transmitters. In the present studies, we examined the influence of NE on the response of LH neurons to the inhibitory amino acid transmitter GABA. Neuronal responses were studied in normal, DOCA hypertensive, and 1% NaCl diet (HSD)-treated rats. Male rats were uninephrectomized and received a DOCA implant (200 mg/kg). They were given 1% NaCl and 0.1% KCl in their drinking water (4-6 weeks). HSD rats received the same treatment, except that no DOCA was given. Extracellularly recorded responses from single LH neurons to iontophoretic pulses (5-50 nA; 10 s duration) of GABA were examined before, during and after NE microiontophoresis (5-50 nA) in anesthetized rats. The results indicated a shift of NE modulatory action from potentiating to antagonizing GABA-induced inhibition. In control rats, NE routinely potentiated GABA depressant responses (19 of 26, 73%), whereas in HSD rats the ability of NE to enhance GABA responses was reduced to 33% of the cases tested (10 of 30). Likewise, NE did not augment, but rather antagonized GABA inhibition in the majority of cells recorded (21 of 35, 60%) from DOCA hypertensive rats. The beta agonist isoproterenol was still capable of potentiating GABA inhibition of LH cells in HSD and DOCA treated animals, suggesting that the change in the capacity of NE to enhance GABA action is not a result of alterations in beta receptor function, but could arise from a modification of the ratio between alpha- and beta-adrenoceptors. NE modulating capability was also altered-in LH neurons responsive to experimentally induced changes in blood pressure. In summary, these findings suggest that chronic HSD and DOCA treatments can alter the modulatory capacities of NE within the LH. These alterations in noradrenergic action within hypothalamic cardiovascular centers might affect the way neurons respond to afferent baroreceptor information, as well as the way they control sympathetic and parasympathetic effector mechanisms. A decrease in the inhibitory capacities of GABA transmission in these areas, due to alterations of NE, may play a role in the genesis of hypertension.

Animals↗
PubMed1989

Electroretinograms to checkerboard pattern reversal in cats: physiological characteristics and effect of retrograde degeneration of ganglion cells.

Pattern electroretinograms (P-ERGs) evoked by alternating checks were studied in cats. Spatial frequency functions for transient and steady-state P-ERG waves showed a bimodal distribution with a preferred frequency at 0.6-0.75 c/deg and a second amplitude increase at frequencies lower than 0.5 c/deg. Decreasing the pattern luminance by 0.5 log units produced a shift of the spatial tuning curve toward lower spatial frequencies. No temporal tuning was noted in the temporal frequency functions. The bimodal distribution suggests that at spatial frequencies higher than 0.5 c/deg, the tuning reflects a 'contrast response' originating in cells with center surround organization. At spatial frequencies below 0.5 c/deg, the 'luminance response' becomes predominant and is generated in cells sensitive to mean luminance changes. Transient and steady-state P-ERGs to medium and high spatial frequencies were abolished by section of the optic nerve, while low spatial frequency stimuli at or below 0.3 c/deg continued to evoke P-ERGs at 1, 5 and 10 months after surgery. Quantitative whole mount retina microscopic examination confirmed the retrograde degeneration of the ganglion cells. It is concluded that both transient and steady-state P-ERGs to small and medium spatial frequencies checks are predominantly related to ganglion cell activity, while P-ERGs to low spatial frequencies reflect preganglionic cell activity.

Animals↗
PubMed1989

Psychological and physiological characteristics of patients with severe idiopathic constipation.

This study prospectively evaluated psychological profiles and selected parameters of colonic and anorectal sensorimotor function in 25 consecutive patients who were referred for severe idiopathic constipation. Measurement of colonic transit of radiopaque markers divided patients into those with normal transit (n = 10) and those with slow transit (n = 15). As measured by the Hopkins Symptom Checklist, patients with normal transit constipation demonstrated significantly higher scores for psychological distress in the global symptoms index and nine clinical subscales than did those with slow transit constipation and gastrointestinal control subjects (n = 25). Both groups with constipation had decreased rectal sensation compared with controls but there was no relationship to rectal compliance or threshold of internal sphincter relaxation. There was also no relation between abnormalities of anorectal parameters, including expulsion dynamics, and psychological profiles in two groups. Measurement of colonic transit and psychological profiles in patients with severe idiopathic constipation identify two groups of patients with respect to possible pathogenesis of symptoms. Accordingly, different therapeutic approaches may be required, one behaviourally and psychologically based and the other focused on the possible modification of disordered colonic transit.

Adolescent↗
PubMed1981

Spontaneous diabetes mellitus in the New Zealand white rabbit: physiologic characteristics.

Spontaneous diabetes mellitus has been observed in a female New Zealand white rabbit. By inbreeding of this individual and her offspring, 39 litters comprising 157 animals have been studied and a closed colony of diabetic rabbits established. Three groups of animals can be identified. Twenty-nine (19%) have overt diabetes characterized by fasting hyperglycemia and depressed intravenous glucose stimulated serum insulin levels. This abnormality is seen between 1 and 3 yr of life. Forty-three of the animals (27%) have developed abnormal glucose disposal with normal or slight elevations in fasting serum glucose levels. Glucose stimulated insulin levels are also significantly lower in the rabbits with abnormal glucose disposal. The remaining 85 animals (54%) exhibit no apparent abnormalities of glucose metabolism. All animals with overt diabetes pass through a stage in which glucose disposal as measured by k values is less than 1.0, a value not observed in normal animals. Fasting and arginine stimulated glucagon levels were no different in 4 diabetic animals and 7 normal colony rabbits. Insulin therapy corrected the hyperglycemia in the diabetic rabbits. Insulin was withheld in 5 diabetic rabbits and serum and urinary glucose and ketones were measured for 9 days. Despite marked increases in serum and urinary glucose, only mild ketonemia was observed. The relatively late onset of diabetic symptoms, lack of obesity, severe hyperglycemia, and depressed insulin secretion without ketoacidosis make this a model with many of the characteristics of insulin responsive diabetes as seen in nonobese human adults.

Acetoacetates↗
PubMed1996

Effect of anabolic steroids on behavior and physiological characteristics of female mice.

Adult female mice were exposed to a combination of four anabolic-androgenic steroids for 9 weeks at doses that were either one or five times the androgenic maintenance level for male mice. Relative to control females, steroid treatment depressed gonadotropin secretion and increased both dry body weight and fat content but without an increase in food intake. Steroid treatment depressed spontaneous use of a running wheel and open-field activity, and it increased aggressiveness. It also eliminated a behavior related to encounters between the sexes--the rejection of genital inspection. There was no effect of steroid treatment on the time required to recover from 10 h of enforced running on a treadmill. Overall, regardless of the test or measure, there was little or no difference in the effect of the high and low dose of steroids. This indicates a threshold of response below the low dose used in these studies, which itself is probably well below that used by many female athletes and body builders.

Adipose Tissue↗
PubMed1985

Organ culture of adult cockroach CNS: ultrastructural and physiological characteristics.

The abdominal nerve cord of adult Periplaneta americana has been maintained in culture for up to 5 weeks. The ultrastructural appearance of in vitro cords resembles that of in vivo cords although some degeneration of glia may occur during the first 2 weeks in culture. The glial cells most affected are those which make up the perineurium. The blood-brain barrier, formed by the perineurium in vivo, breaks down in vitro. Despite this, normal action potentials were recorded from giant axons in 1 month old cultured connectives.

Action Potentials↗
PubMed1988

Effects of nitrogen dioxide on biochemical and physiological characteristics of soybean.

One month old soybean (Glycine max (L.) Merrill) cv. 'Williams' plants were exposed to nitrogen dioxide (NO2 at 0.1, 0.2, 0.3, and 0.5 microl liter(-1) and carbon filtered air (control), 7 h per day for five days, under controlled environment. Data were collected on net photosynthetic rate (PN), stomatal resistance (SR), and dark respiration rate (DR), immediately following the fifth day of exposure and 24 h after termination of exposure. Chlorophyll a (Ch a), chlorophyll b (Ch b), total chlorophyll (tot Ch) and foliar nitrogen (N) were measured before and after exposures. Growth characteristics--relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), and root shoot ratio (RSR) -- were computed for treated plants using standard growth equations. Increases of 18% and 23% in PN were observed immediately following exposure to 0.2 microl liter(-1) NO2 and after 24 h recovery period, respectively. With 0.5 microl liter(-1) NO2 treatment, reductions in PN of 23% and 50% were observed, immediately after exposure and following 24 h recovery, respectively. DR rates with 0.2 l liter(-1) treatment were higher than the control. Chlorophyll a and tot Ch showed significant reduction with 0.5 microl liter(-1) NO2 treatment. The percent reduction in Ch a and tot Ch with 0.5 microl liter(-1) NO2 were 45% and 47%, respectively. Increases in foliar nitrogen content after 0.2 and 0.3 microl liter(-1) NO2 treatments were 46% and 69%, respectively. Nitrogen dioxide at 0.5 microl liter(-1) reduced RGR and NAR by 47% and 51%, respectively. Leaf area ratio was 42% higher in 0.5 microl liter(-)1 NO2 treated plants, compared with the control; this increase was insufficient to compensate for the decrease in NAR resulting in a net decline in RGR. Nitrogen dioxide up to 0.2 microl liter(-1) increased PN and foliar-N content of soybean. With 0.5 microl liter(-1) NO2, significant decreases were observed in PN, leaf chlorophyll, foliar-N, NAR and RGR. Nitrogen dioxide up to 0.2 microl liter(-)1 has a favorable influence on overall growth characteristics of soybean; however, inhibitory effects were seen with NO2 treatment at 0.5 microl liter(-1).

Journal Article↗
PubMedDate not supplied

Some physiologic characteristics of the electrodermal reflex in the cat.

The amplitudes of electrodermal reflexes evoked in intact cats were compared under a variety of anesthetic conditions. Electrodermal reflexes were elicited in both decerebrate and spinal preparations with and without anesthesia. Reflex amplitude was significantly depressed in the anesthetized preparation after decerebration or spinal transection. In contrast, spinal transection performed after decerebration in unanesthetized preparations significantly increased the amplitude of the reflex. The evidence presented in this study supports the concept of a primarily inhibitory lower brainstem system with regard to this reflex. The relative stability of the reflex amplitude in the anesthetized cat suggests that this reflex system could be useful in the analysis of the effects of drugs acting on the central nervous system.

Anesthesia↗
PubMed1994

Physiological characteristics, antimicrobial susceptibility and serotypes of Pasteurella anatipestifer isolated from ducks in Thailand.

Twenty isolates of Pasteurella (Moraxella) anatipestifer from ducks with serositis and septicemia in Thailand between 1988 and 1989 were characterized by various tests. Eighteen isolates fermented glucose and maltose, 3 fructose and 1 each mannose, arabinose, trehalose or sorbitol. All isolates produced gelatinase but not urease, while 2, 3, 5 and 6 produced indole, were CAMP positive, and were proteolytic for milk and coagulated serum respectively. Seven enzymes, phosphatase alkaline, esterase (C4), esterase lipase (C8), leucine arylamidase, valine arylamidase, phosphatase acid and phosphoamidase were detected from all the isolates. The isolates were highly susceptible to ampicillin, erythromycin, penicillin G and tylosin. Gel-diffusion precipitin tests demonstrated that serotype 1 was most prevalent (60%) and serotype 6 followed (5%). Seven isolates (35%) were untypable. These results indicated that P. anatipestifer of serotype 1 played an important role in recent outbreaks of the disease in Thailand.

Animals↗
PubMed1991

The physiologic characteristics of relative pupillary block.

In biometric photographs of 13 patients, we quantified the iris contour in eyes with central anterior chamber depths ranging from 1.9 to 3.4 mm (epithelium to lens surface). This actual profile was compared to that predicted by a theoretical analysis of the forces acting on the iris. The average discrepancy between the calculated actual and the theoretically predicted iris position was only -0.01 to +0.03 mm. The close agreement validates the model under normal conditions and in the presence of relative (nonsynechial) pupillary block. The theoretical iris shape may not occur under conditions that violate the underlying physical assumptions of the mathematical model, such as when iridectomy eliminates the pressure difference between the anterior and posterior chamber or when synechiae introduce additional forces on the iris other than the ones included in the analysis.

Anterior Chamber↗
PubMed2001

Physiologic characteristics of canine skeletal muscle: implications for timing skeletal muscle cardiac assist devices.

BACKGROUND: Optimal clinical stimulation for skeletal muscle cardiac assist systems (such as dynamic cardiomyoplasty) is not clearly defined. The pressure-generating capacity of canine skeletal muscle ventricles (SMVs) at a variety of preloads and stimulation frequencies was examined as was time for SMVs to develop peak pressure. METHODS: SMVs were analyzed just after construction and after 3 months of electrical conditioning. Pressure generation and time to develop peak pressure were determined using a distensible mandrel. RESULTS: Higher preloads resulted in increased pressure generation; conditioned SMVs generated significantly less pressure than unconditioned SMVs. Increasing stimulation frequency from 20 to 50 Hz increased pressure-generating capacity; increases beyond 50 Hz did not result in further increases. Time to 90% peak pressure was least at 10 HZ and 65 Hz. CONCLUSIONS: Higher stimulation frequencies and preloads result in a more quickly contracting muscle, which generates more pressure. Midrange stimulation frequencies of 30 Hz provide optimal muscle strength and minimize time to develop peak pressure. Initiation of contraction should begin before the time maximal pressure is desired.

Animals↗
PubMed1988

Selection of intestinal segments for bladder substitution: physical and physiological characteristics.

Detubularized bowel segments provide greater capacity at lower pressure and require a shorter length of intestine than do intact segments. Four factors account for their superiority: 1) their configuration takes advantage of the geometric fact that volume increases by the square of the radius so that a patch or pouch has a larger diameter than a tube, 2) they accommodate to filling more readily because, as LaPlace's law states, the container with the greater radius and, thus, the greater mural tension will hold larger volumes at lower pressure, 3) compliance is superior to that of the tubular bowel and 4) contractile ability is blunted by the failure of contractions to encompass the entire circumference. For these reasons detubularized segments store more urine at lower pressures.

Biophysical Phenomena↗
PubMedDate not supplied

Anatomical and physiological characteristics of perineal muscles in the female rabbit.

Little information is available on the participation of the perineal striated muscles in female reproductive processes. Here, we describe the gross anatomy and innervation of two striated perineal muscles in the female rabbit, the bulbospongiosus (BSM) and ischiocavernosus (ISM), and analyze their reflex electromyographic (EMG) activity in response to stimulation of the perigenital skin and vaginal tract. Twenty-four mature chinchilla-breed rabbit does were used: 12 to describe the anatomy and innervation of the muscles, 9 to determine reflex EMG activity of the muscles in response to stimulation of the perigenital skin and specific levels of the vaginal tract and 3 to analyze the effect of contraction of the muscles on intravaginal pressure. Both muscles were well developed, with their fibers originating at the ischiadic arch and inserting onto the ligamentum suspensorium clitoridis. Branches of the clitoral and perineal nerves innervated the BSM and ISM, respectively. Bilateral electrical stimulation of these nerves provoked retraction of the clitoral sheath and an increase in intravaginal pressure at the level of the perineal vagina. Whereas neither muscle responded to stimulation of the perigenital skin, both were reflexively activated during mechanical stimulation of the inner walls of the perineal vagina. Prolonged cervical stimulation inhibited this reflex. Thus, in reproductive processes such as copulation and/or parturition, the contraction of these muscles may be induced during stimulation of the perineal vagina.

Animals↗