Production, assay and partial characterization of guinea pig interleukin 2

Optimum conditions for the production and assay of guinea pig interleukin-2 (IL-2) have been established. The mitogenic activities of serial dilutions of guinea pig IL-2 preparations were compared in cultures of guinea pig peripheral blood lymphocytes prestimulated for 7 days with phytohemagglutinin (PHA) used at 1 microgram/ml. Parallel log dose-log response curves were used for quantitative comparisons. Optimum IL-2 yields were obtained from cultures of lymph node lymphocytes stimulated for 20 h with Concanavalin A (ConA) at 5 micrograms/ml. Guinea pig T cell lines reactive to mycobacterial antigens were propagated for several months using our IL-2 preparations. The molecular weight of guinea pig IL-2 was estimated to be 30,000 using S-200 gel filtration. The species specificities of guinea pig, human, mouse and rat IL-2s were examined. It was shown that guinea pig T lymphocyte blasts were stimulated only weakly with human IL-2 and not at all with mouse and rat IL-2.

Guinea pig MSEL-neurophysin. Sequence comparison of eight mammalian MSEL-neurophysins

The amino acid sequence of guinea pig MSEL-neurophysin has been determined using tryptic peptides derived from the performic acid-oxidized protein and staphylococcal proteinase peptides obtained from the reduced-carboxamidomethylated neurophysin. Guinea pig MSEL-neurophysin consists of a 93-residue polypeptide chain that shows 12 substitutions and 2 deletions when compared to bovine MSEL-neurophysin. It displays the highest number of variations among known mammalian MSEL-neurophysins. These variations are mainly found in the C-terminal region (residues 88-93). Moreover guinea pig MSEL-neurophysin, like rat homologous protein, exhibits substitutions in positions 2, 5, 29 and 81 and lacks an arginine in the penultimate position. Comparison between eight mammalian MSEL-neurophysins reveals a highly conserved region (residues 1 to 88) and a hypervariable region (residues 89 to 93/95). On the other hand the eight species examined are endowed with arginine vasopressin except pig, which has a lysine vasopressin. In the vasopressin-MSEL-neurophysin precursor, the hormonal moiety and the MSEL region of neurophysin (residues 1-9) are encoded by a common exon in ox, rat and man; it can be concluded that this exon is evolutionarily conservative in contrast to the one encoding the C-terminal region of MSEL-neurophysin.

Extra- and intracellular HRP analysis of the organization of extraocular motoneurons and internuclear neurons in the guinea pig and rabbit

The distribution of extraocular motoneurons and abducens and oculomotor internuclear neurons was determined in guinea pigs by injecting horseradish peroxidase (HRP) into individual extraocular muscles, the abducens nucleus, the oculomotor nucleus, and the cerebellum. Motoneurons in the oculomotor nucleus innervated the ipsilateral inferior rectus, inferior oblique, medial rectus, and the contralateral superior rectus and levator palpebrae muscles. Most motoneurons of the trochlear nucleus projected to the contralateral superior oblique muscle although a small number innervated the ipsilateral superior oblique. The abducens and accessory abducens nuclei innervated the ipsilateral rectus and retractor bulbi muscles, respectively. The somata of abducens internuclear neurons formed a cap around the lateral and ventral aspects of the abducens nucleus. The axons of these internuclear neurons terminated in the medial rectus subdivision of the contralateral oculomotor nucleus. At least two classes of guinea pig oculomotor internuclear interneurons exist. One group, located primarily ventral to the oculomotor nucleus, innervated the abducens nucleus and surrounding regions. The second group, lying mainly in the dorsal midline area of the oculomotor nucleus, projected to the cerebellum. Intracellular staining with HRP demonstrated similar soma-dendritic organization for oculomotor and trochlear motoneurons of both guinea pigs and rabbits. Dendrites of oculomotor motoneurons radiated symmetrically from the soma to cover approximately one-third of the entire nucleus, and each motoneuron sent at least one dendrite into the central gray overlying the oculomotor nucleus. In both species, a small percentage of oculomotor motoneurons possessed axon collaterals that terminated both within and outside of the nucleus. The dendrites of trochlear motoneurons extended into the medial longitudinal fasciculus and the reticular formation lateral to the nucleus. Our data on the topography of motoneurons and internuclear neurons in the guinea pig and soma-dendritic organization of motoneurons in the guinea pig and rabbit show that these species share common organizational and morphological features. In addition, comparison of these data with those from other mammals reveals that dendritic complexity (number of dendrites per motoneuron) of extraocular motoneurons exhibits a systematic increase with animal size.

Thermodilution cardiac output determination in the guinea pig

Thermodilution cardiac output was compared with simultaneously determined aortic flow in 5 guinea pigs during thoracotomy. Total cardiac output was affected by volume expansion, adrenergic stimulation, and the volume of hemorrhage. For the equation y = mx, where y is aortic flow, x is thermodilution cardiac output, and m is the slope of the regression line, m = 0.88 +/- 0.02 (95% confidence interval). The SE of the regression was 27.8 ml/min. Thermodilution may have been overestimated because the aortic flow measurement did not take into account the coronary arterial blood flow, which is approximately 4% of total cardiac output in the guinea pig. Indicator loss (ie, temperature) also may be an important factor in the calculation of cardiac output, as determinations of thermodilution cardiac output were affected by sampling site in the guinea pig. Thermodilution appears to be a useful and reliable means of determining cardiac output in the guinea pig.

An ultrastructural analysis of the sympathetic neuromuscular junctions on arterioles of the submucosa of the guinea pig ileum

The relationship of the varicosities of sympathetic postganglionic nerve terminals to the smooth muscle cells of arterioles in the submucosa of the guinea pig ileum has been investigated quantitatively by electron microscopy. Longitudinal sections were cut through arterioles about 50 micron in diameter after fixation in vitro or in situ under pressure. About 13% of the varicosities in individual ultrathin sections made contact with the outer surface of the smooth muscle cells. The neuromuscular junctions resembled those in skeletal muscle: the basal laminae of the axon bundle and of the smooth muscle were fused, and synaptic vesicles were accumulated close to the region of fusion. When individual varicosities were examined in serial sections, 92% and 83% in two preparations were found to form junctions of this kind. Most of the noncontacting varicosities were bare of Schwann cell toward the arteriolar surface and separated from it by less than 200 nm. Almost all axon profiles contained synaptic vesicles with electron dense cores after exposure to 5-hydroxydopamine. In electrophysiological experiments, ionophoretic application of noradrenaline to the arteriolar surface along the nerve bundles (demonstrated subsequently by fluorescence histochemistry) produced responses resembling those evoked by nerve stimulation. These anatomical and physiological data, taken together with the evidence for quantal release in this preparation (see Hirst et al., '85), suggest that neuromuscular transmission involves the rare release of a quantum of noradrenaline at discrete points on the smooth muscle membrane.

Substance P-inducing massive postmortem bronchoconstriction in guinea pig lungs

To further examine the role that substance P plays in initiating the observed massive postmortem bronchoconstriction in guinea pig lungs and to explore the role of neural reflex in this airway spasm, six groups of animals were employed: control (n = 6), morphine (n = 6), substance P (n = 5), chronic capsaicin pretreatment + substance P (n = 5), tetrodotoxin (TTX) + acute capsaicin (n = 4), and chlorisondamine + acute capsaicin (n = 5). Pressure-volume curves were performed prior to and following the initiation of artificial pulmonary perfusion with 1% bovine serum albumin and 5% dextran in Tyrode's solution. A decrease in inflation volume (the lung volume between transpulmonary pressure of 0 and 30 cmH2O during inflation) was used as an index of bronchoconstriction. In control animals, inflation volume decreased to 20-30% of the base-line value at 15-30 min of perfusion, indicating massive bronchial constriction during this time period. Morphine (an agent inhibiting substance P release) significantly attenuated the spasm, whereas the presence of substance P in the perfusate markedly enhanced the constriction. Depletion of endogenous substance P by chronic capsaicin pretreatment did not affect exogenous substance P-induced spasm. Acute capsaicin-induced bronchoconstriction was significantly attenuated by TTX but was not affected by the ganglionic blocking agent, chlorisondamine. These data suggest that substance P initiates the massive postmortem bronchoconstriction in guinea pig lungs and that substance P is released by local stimulation of sensory nerve endings via axonal reflex.

Lordosis behavior in males of two inbred strains of guinea pig

The lordosis behavior of male guinea pigs from inbred strains 2 and 13 was examined. Significantly more isolated gonadally intact males of strain 2 than strain 13 displayed lordosis. Castration did not decrease the display of lordosis. In castrated strain 2 males, those which showed lordosis did not have higher plasma androgen, estrone or estradiol levels than those which did not show lordosis. They also did not differ hormonally from ovariectomized strain 2 females even though strain 2 females never showed lordosis without hormone replacement. Although the lordosis shown by strain 2 males was not related to endogenous gonadal hormone levels, estradiol benzoate (EB) administration facilitated lordosis. EB had no clear effect on lordosis in strain 13 males. Progesterone after EB priming had no further facilitative effect in males of either strain. These results indicate that lordosis is more readily elicited from strain 2 than strain 13 males. Furthermore, lordosis in strain 2 males is not dependent upon gonadal hormones for its display although it is facilitated by EB (but not progesterone).

Effects of induced hypothermia on organ blood flow in a hibernator and a nonhibernator

Regional blood flow and hemodynamic variables during induced hypothermia were compared in six guinea pigs and four hedgehogs. Tracer microspheres were used for blood flow measurements, since this technique is more accurate than the earlier method (86Rb+ distribution) used for cardiac output distribution measurements in hibernators. Heart rate and blood pressure decreased with reduced temperature in a comparable fashion in the two species, while cardiac output was less affected in the hedgehogs than in the guinea pigs. Total peripheral resistance increased in both species. At 34 degrees C the hedgehogs had a higher myocardial blood flow per gram tissue than the guinea pigs and it was not reduced in the hedgehogs when the body temperature was lowered to 22 degrees C, whereas in the guinea pigs it was markedly reduced. The brown adipose tissue of the hedgehogs showed a fourfold increase in blood perfusion at 22 degrees C when compared with 34 degrees C. In the hedgehogs the fractional distribution of cardiac output to the myocardium increased with decreasing body temperature, while the renal fraction decreased. In the guinea pigs, on the other hand, the fractional distribution of cardiac output to the myocardium remained unchanged but increased to the kidneys.

Guinea pig glucagon differs from other mammalian glucagons

Mammalian glucagon is thought to be highly conserved. Glucagons from pig, cow, human, rat, and hamster have identical amino acid sequences, whereas the amino acid contents of rabbit and camel glucagons are consistent with this 29-amino acid sequence. It had earlier been reported that guinea pig (GP) glucagon contains 40 amino acids. In the current study, glucagon was purified from two GP pancreata by a series of three HPLC steps after acid-alcohol extraction and acetone precipitation. GP glucagon is a 29-amino acid peptide that differs from other mammalian glucagons by substitution of Gln for Asp in position 21, Leu for Val in position 23, Lys for Gln in position 24, Leu for Met in position 27, and Val for Thr in position 29. In view of the marked changes in the COOH-terminal of GP glucagon, receptor binding studies were performed using both rat and GP liver membranes. Labeled synthetic porcine glucagon has similar binding in the two systems and its binding is inhibited to a similar degree by synthetic porcine glucagon, whereas GP glucagon is 10-fold less potent at inhibiting binding in both systems. This suggests that glucagon receptor binding sites in the GP are evolutionarily more conserved than is GP glucagon.

Effect of a uniform partial denervation of the periphery on the peripheral and central vibrissal system in guinea pigs

In some rodents, somatotopically organized architectonic patterns corresponding precisely to the arrangement of the vibrissae on the face are found in each of the central stations of the trigeminal (V) pathway. Two lines of evidence indicate that these architectonic patterns reflect the level of peripheral innervation. First, in normal mice, the sizes of the individual units within the cortical representation are proportional to the number of fibers supplying the corresponding vibrissal follicles. Second, complete surgical denervation of groups of vibrissae can severely attenuate the sizes of and alter the patterns of their central representations. However, previous studies in this system do not distinguish the effects of the absolute and the relative levels of peripheral innervation on central representations. To address this question, we have studied guinea pigs in which all vibrissae are partially deafferentated before birth by fetal exposure to antibodies against NGF. This approach reduces the absolute level of peripheral innervation in a graded way, and does so uniformly, without changing the pattern of vibrissal innervation. In the most severely affected animals, only 18% of the normal number of V ganglion neurons survive. The effect of this loss on the V system was assessed by comparing the peripheral and central components of the vibrissal system in normal and NGF-deprived animals. Peripheral fibers from the V ganglion neurons, including those to the vibrissae, are less reduced in number (50%) than expected. The number of peripheral fiber fascicles is also decreased. In contrast, neither the patterns nor the areas of the central representations in medulla and cortex differ from those of normal animals. We conclude that 18% of the normal number of V ganglion cells is sufficient to establish normal central architectonic patterns and the size of the central vibrissal representations is independent of the absolute magnitude of peripheral innervation. These observations are of relevance to understanding the role of NGF on the morphogenesis of central somatosensory pathways, the effects of "mismatches" between peripheral innervation, and the development of projections to central targets in the mammalian brain, and provide new data for understanding competitive interactions in the developing central and peripheral trigeminal system.

Normal electrocardiogram in guinea pig

For establishing normal mean values of the parameters of the electrocardiographic curve and their standard deviations 50 male guinea pigs were studied. The directions of temporary vectors of atrial (AP) and ventricular (AQRS) depolarization times, and ventricular repolarization time (AT) were determined, and the position of the heart was evaluated. In all animals limb leads I, II, III, aVR, aVL, aVF were used, and in 38 animals additionally the precordial leads V1, V2, V3, V4, V5, V6 were applied. The investigations were done by a non-invasive method with a specially designed plate making possible immobilization of the animals in supine position under general anaesthesia with urethane. In 10% of the animals abnormalities were detected in the ECG curve and these guinea pigs were eliminated from further analysis. The investigations showed that, after consideration given to the differences in the ECG curves in relation to man, guinea pigs might be used for preclinical cardiological studies.

Electrocochleography for different electrode positions in guinea pig

In 20 guinea pigs the relation between the electrode position on the cochlear surface and the recorded potentials was studied. We found the greatest AP amplitudes at the free lateral part of the cochlea; AP amplitudes decreased when the electrode was moved into the direction of the attachment of the cochlea to the petrous bone. Moving the electrode from the basal turn to the apex the maximal AP amplitude was found at the apex. The most negative SP was always recorded from the apex. This negative SP became smaller when the electrode was moved to the basal turn. Near the round window a small negative SP was recorded for 1 kHz stimuli and a positive SP for most 4 kHz stimuli. Moving the electrode from the free lateral part of the cochlea to the place of attachment to the petrous bone the magnitude of the SP decreased in a fashion similar to the AP amplitude. For 4 kHz stimuli we recorded a range of SP-AP ratios from -0.21 to +0.50 merely by varying the electrode position. Thus the SP-AP ratio highly depends on the electrode position.

Cold adaptation in guinea pig at level of isolated brown adipocyte

Isolated brown adipocytes were prepared from guinea pigs acclimated to 28 degrees C or exposed to 4-8 degrees C for periods of up to 3 wk. Cells from warm-adapted animals retained respiratory control when stimulated with norepinephrine. Cells from guinea pigs exposed to cold for 4-21 days showed a much greater respiratory response to norepinephrine due to enhanced uncoupling rather than enhanced substrate supply. After 7 days of cold acclimation, norepinephrine-stimulated respiration became uncontrolled and was limited only by the maximal respiratory capacity of the mitochondria. Three weeks of cold acclimation were accompanied by a doubling of total cell number, a doubling of the mitochondrial protein per adipocyte, and a sixfold increase in the norepinephrine-stimulated respiration per in situ mitochondrion with no change in respiratory chain capacity. The induction of norepinephrine-stimulated respiration correlated with the appearance of high-affinity purine nucleotide binding sites on the mitochondria, diagnostic of the uncoupling protein. If the results are extrapolated to the whole animal, they indicate that brown adipose tissue makes little contribution to thermogenesis in the warm-adapted guinea pig but may account for most or all the increment seen on cold adaptation.

An unusual function for the medial pterygoid muscle in the guinea pig

This muscle has some physiological properties resembling those of jaw-opening muscles. Biomechanical analysis showed that, because of the anatomical peculiarities of the feeding apparatus in caviid rodents, the action of the muscle changes from closing to opening as the mandibular condyles are protruded in the groove-like mandibular fossa. This unusual changing function may be useful in producing the ventral, medial and anterior power stroke of mastication.

Contractile properties and histochemistry of extraocular muscle in the pigmented and the albino guinea pig

The inferior oblique muscles of pigmented and albino guinea pigs were compared with respect to contractile and histochemical properties. No differences were found between the 2 kinds of animal in twitch and tetanic response or in fatigue properties. They also had the same fiber composition and fiber and capillary densities of their inferior obliques. These findings indicate that differences in eye muscle previously demonstrated and Siamese (albino) cats are related to the state of binocular vision and not to genetic variations between pigmented and albino animals.

The development of electrocortical activity in the fetal and neonatal guinea pig

We have developed techniques for chronic recording of electrocortical activity in the fetal and neonatal guinea pig with subsequent power spectral analysis. Thirty-four unanesthesized, unrestrained pregnant Hartley guinea pigs were studied 1 to 14 days following surgical procedures. Twelve neonatal animals instrumented during the first week of life were studied at 3 to 30 days. Spontaneous, undifferentiated electrocortical activity was recorded from the youngest fetuses studied, with high-voltage slow activity appearing at 50 days' gestation. Cycling electrocortical activity and sleep spindles could be observed in the late-term fetal and neonatal animals, with rapid eye movements and behavioral state defined in the latter. Power spectral analysis demonstrated more predominant delta activity, faster beta frequencies, and better-developed sleep spindles in the neonatal animal as compared to the fetus.

Ventilation and oxygen consumption in the guinea pig

Respiratory values were determined in guinea pigs studied under normal laboratory conditions in Denver. The effects of anesthesia and acute hypercapnia were also assessed. In normal laboratory conditions, VO2 and VE were proportional to body weight (BW). Specific VO2 and VE for small guinea pigs (mean BW: 269 g) were 1.14 +/- 0.04 (SEM) and 57.5 +/- 3.9 ml/g X h, respectively, compared to 0.82 +/- 0.03 (P less than 0.001) and 29.9 +/- 0.8 ml/g X h (P less than 0.001), respectively, for large animals (mean BW: 817 g). Tidal volume (VT) was related to BW by the following equation: VT (ml) = 3.97 X 10(-3) BW (g) + 2.05 (r = 0.82; P less than 0.001). During anesthesia VO2 decreased 25-63% and VE was reduced by 45% in those animals having the largest change in VO2. In hypercapnia, VE was more than twice that in normocapnia primarily due to a 75-95% elevation in VT.

Ventricular action potentials, ventricular extracellular potentials, and the ECG of guinea pig

Action potentials were recorded from different regions of the guinea pig ventricle to characterize regional differences in waveform configuration, and to acquire insight into the generation of the T-wave of the electrocardiogram. Isolated tissue preparations were driven at 1 Hz, and microelectrodes were used to map accessible surface regions of the epicardium, endocardium, and septum. There were minimal differences in regional resting potentials (mean -87 mV) and amplitudes (mean 122 mV), but Vmax in the epicardium (mean 110 V/sec) was much smaller than elsewhere (mean 247 V/sec). The action potential duration at the -80 mV repolarization level was longest in the papillary muscles (mean 154 msec), shortest in the septum (mean 126 msec), and generally 10-15 msec longer at the base than at the apex. The characteristics of intramural action potentials were inferred from measurements on enzymatically isolated myocytes, the rationale being that most dissociated myocytes originated from intramural cell layers. The action potentials in about 40% of the myocytes had durations similar to those recorded from the tissue surface (110-170 msec), and the remainder ranged from 170-290 msec long. The existence of longer-than-surface action potentials in the ventricle was also inferred from the body surface electrocardiogram and from bipolar electrograms of isolated left ventricles. In both cases, the Q-T intervals could be accounted for only by action potentials longer than those recorded from the ventricular surface.

Effects of cold and hypoxia on ventilation and oxygen consumption in awake guinea pigs

Ventilation and oxygen consumption were measured in awake, unrestrained and unintubated guinea pigs during chronic and acute exposure to cold or hypoxia. Specific VE and VO2 in acute and chronic exposure to cold were more than twice that of animals in normal environmental temperatures. Increased ventilation was mainly due to a 70% greater VT in cold. Cold-acclimated guinea pigs returned acutely to normal temperatures, maintained higher VE and VO2 than that of control animals. Acclimation to cold did not result in respiratory advantages over that of control animals acutely exposed to cold. In hypoxia-acclimated guinea pigs, specific VE was 30% higher than that of control animals due to an elevation in VT; however, VO2 was similar in both groups of animals. In contrast, acute hypoxia did not increase VE in control animals. This lack of ventilatory response to acute hypoxia apparently causes the marked erythropoiesis and the severe increase in hematocrit observed throughout chronic exposure to hypoxia. The high blood viscosity resulting from the increased hematocrit contributes to the right ventricular hypertrophy and cardiac failure in guinea pigs chronically exposed to hypoxia.

Regenerative capacity of retinal axons in the cat, rabbit, and guinea pig

Long-term signs of axonal regeneration were observed in the adult cat, rabbit, and guinea pig retina to follow mechanical or thermal lesions. The axons of surviving ganglion cells displayed signs of growth beginning at the border of the lesions: multiple bifurcations, changes of caliber, and unoriented random course of the fibers. Inspection of the fiber course and retrograde filling with horseradish peroxidase showed that these attempts of regeneration were not successful in terms of reconnection to the brain. None of these axonal changes occurred after early postnatal lesions. The capacity for long-survival regenerative processes after axotomy begins 20 to 50 days after birth in the developing cat retina.

The colonic separation mechanism in the guinea-pig (Cavia porcellus) and the chinchilla (Chinchilla laniger)

In guinea-pig, the concentration of nitrogen and viable bacteria were nearly twice as high in the contents of the colonic furrow compared to the contents of the corresponding lumen. Labelled bacteria infused into the proximal colon of guinea-pigs were transported in the furrow into the caecum. Both species produced two types of pellets, one nitrogen-rich intended for caecotrophy, and one nitrogen-poor delivered as faecal pellets. The furrow is part of a separation mechanism in both species saving bacteria for the animals.