Investigation of epididymal sperm maturation in the golden hamster

During passage of hamster spermatozoa through the epididymis their maturation is shown to involve changes in the sperm head, midpiece (mitochondria) and tail. The sum of these changes results in a dramatic increase in the fertilizing potential of the spermatozoa. When comparable numbers of spermatozoa from the caput or corpus epididymis were injected into one uterine horn of mature females, following ovulation induction, and spermatozoa from the cauda epididymis were injected into the contralateral horn, no fertilization was observed with caput epididymal spermatozoa, 1.7% of oocytes were fertilized by corpus epididymal spermatozoa, whereas 79.5% fertilization was obtained with cauda epididymal spermatozoa. Total sperm numbers increased from caput to corpus to cauda [28.3 +/- 12.2, 40.6 +/- 20.8, 144 [corrected] +/- 62 million, respectively]. The percentage of progressively motile spermatozoa increased from 27.9 +/- 6.4 to 33.8 +/- 4.8 to 70 +/- 10.7 during this passage. Viability, measured by exclusion of the dye, propidium iodide, was significantly less in spermatozoa from the cauda than from the proximal or mid-caput epididymis. The percentage of the live cells that were stained intensely by rhodamine-123 (a measure of mitochondrial membrane potential) increased during epididymal passage from 22.8 +/- 7.8% in the proximal caput epididymis to 57.2 +/- 16.5% in the cauda epididymis. Staining with acridine orange (a measure of DNA packaging in the sperm head) indicated an increase in chromatin condensation in cauda epididymal spermatozoa, when compared to those obtained from the caput or corpus.     

Thermotaxis in golden hamster pups.

Notes that during the 1st 10 days of life, golden hamster pups lack physiological mechanisms for thermoregulation, and are thus ectothermic (i.e., they depend on heat from the environment). In their mother's absence, they conserve heat by burying together, thus reducing the amount of surface area exposed to the air. In the 6 experiments reported here, it is shown that the neonatal pup is extraordinarily sensitive to thermal gradients, and under conditions of heat loss pups demonstrate this sensitivity by moving rapidly away from cooler regions. Results suggest that the pup's high sensitivity is due to spatial and/or temporal integration of thermal information from all parts of its body. Such thermal responsivity would be sufficient to account for the pup's burying behavior in the nest. The thermotaxic response weakens after 8 days of age, probably as a result of decreasing thermal sensitivity and the maturation of competing responses. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The significance of circadian organization for longevity in the golden hamster

INTRODUCTION: Altered patellofemoral biomechanics may result in pain, instability and early involutive processes. Magnetic Resonance Imaging (MRI), with its panoramic capabilities, has proved to be an effective technique in the study of knee extensor complex changes. The diagnostic advantages of dynamic studies of patellofemoral kinetics are reported in the recent scientific literature. We investigated the diagnostic potentials of passive studies of the knee extensor complex with sagittal and axial cine MRI. Then, we developed and optimized an innovative study method overcoming the limitations of the other dynamic techniques for the correct assessment of patellofemoral biomechanics. MATERIAL AND METHODS: We studied the knee with a .2 T permanent magnet dedicated to the limbs and acquired the images in different positions of flexion-extension with T1-weighted SE and T2-weighted GE sequences. We examined 21 healthy volunteers and 37 of 38 patients with anterior knee joint pain of suspected patellofemoral origin. All the images needed for dynamic studies were acquired in about 20 minutes. For the scan planes not to be affected by patellar motion in the different degrees of knee extension, it is necessary to acquire single axial images to be edited in cine motion afterwards. Each acquisition is aligned along sagittal reference planes depiciting always the same patellar aspect. RESULTS: Significant correlations were found between clinical and cine MR findings in 25 patients. In particular we depicted some extensor complex impingement conditions missed at conventional MRI, which clarified the role played by patellar dysplastic changes in cartilage microtraumas. Our technique was accurate, quite easy to perform and repeatable. We performed cost-effective dynamic studies which were useful in the evaluation of patients with anterior knee pain in whom conventional MRI had failed to provide enough information. CONCLUSIONS: Our technique differs from other passive or active dynamic studies reported on in the literature because the patellar volume does not change during acquisitions. This permits to decrease morphological changes and to simplify, on cine MR reconstructions, the specific analysis of patellofemoral dynamics during flexion-extension. Fewer morphological changes also mean a more accurate analysis showing the role of patellar dysplasia in cartilage microtraumas. Our dynamic MR protocol is accurate, easy to perform and to repeat; it allows dynamic studies in the patients with poor static MR findings.     

Muscular composition of the gastric groove in the golden hamster

The golden hamster possesses a forestomach and a glandular stomach. The gastric groove connects the cardia to the glandular stomach and is situated on the lesser curvature of the stomach. The constitution of the muscle fibers in the gastric groove was investigated. The gastric groove consisted of two lips and a groove floor. The muscle coat of the lips was composed of a mixture of smooth and striated muscle fibers. The smooth muscle fibers were components of the cardiac muscle loop. The striated muscle fibers were extensions from the esophageal inner circular muscle layer, and invaded about half the length of the lips. The muscle coat of the groove floor consisted of an inner circular muscle layer made up of smooth muscle fibers, and the outer longitudinal muscle layer of the striated muscle fibers extended from the esophageal outer longitudinal muscle layer. The present study revealed that the muscle coat of the gastric groove in the golden hamster was composed of smooth and striated muscle fibers, and that these striated muscle fibers were extensions of the esophageal muscle coat.     

Sex differentiation of t-e circadian system in the golden hamster

The effect of estradiol benzoate (EB) on free-running circadian activity rhythms was studied in gonadectomized hamsters maintained in constant dim illumination. EB shortened the period (tau) of the female, but not of the male circadian activity rhythm. Responsiveness of the circadian system to EB was subject to sexual differentiation. The circadian period of wheel running by female hamsters given a single injection of testosterone propionate on the day of birth did not shorten in response to EB in adulthood. This failure to respond to EB also was observed in normal male hamsters, and was different from the response shown by normal females. Preliminary data suggest that tau of the activity rhythm of males castrated on the day of birth is shortened during EB treatment in adulthood. The differential effects of estradiol on tau are related to anatomic differences between the sexes in neural connections of the substrate for circadian rhythms.     

Neural correlates of species-typical behavior in the Syrian golden hamster.

The behavior of a total of 84 Syrian golden hamsters with lesions to the medial frontal cortex (MF), orbital frontal cortex (OF), cingulate cortex (CING), posterior cortex (POST), hippocampus (HPC), septum (SEPT), or amygdala (AMYG) was compared with that of 12 control hamsters in a variety of situations, including weight regulation, food hoarding, nest building, neophobia, bait shyness, sex preference, territorial aggression, and shock-induced aggression. The behavior of Ss with OF or AMYG lesions was doubly dissociable from the behavior of Ss with MF, HPC, or SEPT lesions. The OF and AMYG lesions produced severe weight losses, and all OF Ss were aphagic and adipsic and subsequently died. The HPC, MF, and SEPT lesions severely disrupted hoarding and nest building, whereas the other lesions affected neither. None of the lesions impaired the development of bait shyness when a sucrose solution was paired with sickness, but both AMYG and SEPT lesions may have produced a mild impairment when an NaCl solution was paired with sickness. Only amygdala lesions produced consistent behavioral changes on the social tests. Neither cingulate nor posterior cortical lesions significantly altered behavior on any of the tests. Results support the idea that different forebrain regions can be functionally dissociated by using behavioral tests that are biologically significant. (56 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social learning in the golden hamster (Mesocricetus auratus).

Investigates whether golden hamster (Mesocricetus auratus) pups can acquire a new behavior by interacting with an experienced adult conspecific. The behavior consisted of using teeth and forepaws to retrieve a piece of food dangling from a small chain. Instrumental learning techniques were used to train the demonstrators. Four groups of pups were exposed to different kinds of social experience. In the 1st group, the pups interacted with their skilled mother, in the 2nd group, they did the same with their inexperienced mother, in the 3rd group, they interacted with inexperienced littermates; and in the 4th group, the pups were tested individually. At the end of an acquisition period, the pups were tested individually to assess their performance. Results demonstrate that interacting with a skilled mother has a remarkable effect on the acquisition of a new feeding behavior by hamster pups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Leishmania donovani: acquired resistance to visceral leishmaniasis in the golden hamster

Multiple rough endoplasmic cisternae were found in "C" cells of the adult rat, at interphase. They are considered to be normal constituents of "C" cells. Their morphological relation to rough endoplasmic reticulum and their close proximity to mitochondria, Golgi dictyosomes and secretory granules suggest that they may have a role in the secretory activity of this endocrine cells.     

Melatonin effect on the cyclic GMP system in the golden hamster retina

Melatonin effect on retinal cyclic GMP accumulation, guanylate cyclase activity, cyclic GMP content and cyclic GMP phospho-diesterase activity was examined in the Syrian hamster retina. Melatonin increased significantly cyclic GMP accumulation at picomolar concentrations and in a time-dependent manner. The kinetic analysis of guanylate cyclase activity revealed a significant increase of both apparent Vmax and K(m), induced by 10 nM melatonin. The effect of melatonin was higher in the absence, than in the presence of the phoshodiesterase inhibitor (IBMX), suggesting an effect on cyclic GMP catabolism. Phosphodiesterase activity was significantly decreased by melatonin. The results show a dual effect of melatonin on cyclic GMP levels, i.e. by increasing the synthesis and inhibiting the degradation, both resulting in an increase of cyclic GMP levels. Taking into account the key role of cyclic GMP in visual mechanisms, the results would suggest the participation of melatonin in retinal physiology.     

Effects of corticotropin-releasing factor on circadian locomotor rhythm in the golden hamster

Stress produces a reduction in the amplitude of some circadian rhythms. The neurochemical mechanisms underlying stress-induced changes in circadian rhythms are not known. To investigate a possible role of corticotropin-releasing factor (CRF) in this phenomenon, three related experiments were carried out: activity rhythms of male golden hamsters (10/14 hours light/dark entrained, lights on at 0800 h) were measured 1) following the intracerebroventricular administration of CRF (0.5, 1.0, 2.0, or 4.0 microg) at two different times of day, 2) following social stress (30-min resident-intruder confrontation), 3) and following the administration of the CRF-antagonist alpha-helical CRF9-41 (2.0 microg) prior to a 15-min resident-intruder confrontation. CRF produced a significant, dose-related decrease in circadian rhythm amplitude following administration in the morning hours, but not in the afternoon. CRF also induced transient increases in activity post injection concomitant with an activation of the hypothalamic-pituitary-adrenocortical (HPA) system. Stress similarly reduced the amplitude of activity patterns and stimulated the HPA system. The stress-induced depression of circadian rhythm amplitude was significantly attenuated following alpha-helical CRF9-41. These data suggest a role for CRF in the stress-related modulation of circadian locomotor rhythm amplitude.     

Effects of epididymal occlusion on sperm maturation in the hamster

Combination chemotherapy with adriamycin and DTIC was used in 102 evaluable patients under 15 years of age who had previously treatted metastatic solid tumors. Responses, defined as 50% or more reduction in all tumor masses, occured in 10 out of 27 patients with neuroblastoma, 3 out of 8 patients with Wilms tumor, 7 out 15 patients with Ewing sarcoma, 2 out of 6 patients with osteosarcoma, 5 out of 13 patients with rhabdomyosarcoma, and 15 out of 33 patients with miscellaneous tumors which included a patient who had a complete regression of an extensive juvenile angiofibroma. Response rate to combination chemotherapy with adriamycin and DTIC in patients with Ewing sarcoma was significantly superior to the response rate obtained with adriamycin alone in another Southwest Oncology Group Study. Major toxicity included nausea, vomiting, myelosuppression, high incidence of pneumocystis carinii pneumonia (5 patients) and congestive heart failure (4 patients). There was 7 drug-associated deaths due to sepsis (1), pneumocystis carinii pneumonia (4), and congestive heart failure (2).     

Uneven distribution of desmosterol and docosahexaenoic acid in the heads and tails of monkey sperm

Previously we demonstrated high concentrations of desmosterol and docosahexaenoic acid (DHA, 22:6 n-3) in monkey testes and sperm. Desmosterol, a cholesterol precursor, is not present elsewhere in the body. High concentrations of DHA are found elsewhere only in the retina and brain. To examine the distribution of these compounds in the heads and tails of sperm, we separated them and determined their sterol, fatty acid, and phospholipid molecular species composition. Desmosterol predominated in tails (134.4 vs. 1.7 microg/10(9) cells in heads). The cholesterol content was also greater in the tails (66.2 vs. 30.3 microg/10(9) cells in heads). Sperm tails had more polyunsaturated fatty acids than the heads (34.1 vs. 12.1% of total fatty acids) which resulted mainly from the higher contents of DHA (19.6 vs. 1.1%) and arachidonic acid (20:4 n-6) (6.4 vs. 1.6%) in the tails. These differences in fatty acid composition occurred mainly in phospholipids: phosphatidyl choline and phosphatidyl ethanolamine for n-3 fatty acids and phosphatidyl serine and cardiolipin for n-6 fatty acids. Fifteen phospholipid molecular species were identified. Sperm tails had more molecular species containing unsaturated fatty acids than the heads. Our results reveal the large differences in membrane lipid composition between the heads and tails of sperm. Most (99%) of the desmosterol and DHA in sperm is located in the tail. These differences may be responsible for the different functions of these two components of sperm. The large number of double bonds in DHA, six, and in desmosterol, two, may contribute to the membrane fluidity necessary for the motility of the sperm tails.     

Flavor–calorie learning in the golden hamster (Mesocricetus auratus).

Golden hamsters (Mesocricetus auratus) were repeatedly exposed to conditioning diets differing in both caloric density (1.98 or 5.01 kcal/g) and flavor (anise or clove) to demonstrate flavor-calorie learning. During testing, hamsters were presented with 2 jars that both contained a test diet consisting of a mixture of equal amounts of the conditioning diets; the test diet in 1 cup contained the flavor previously associated with the high-calorie diet, and the test diet in the other cup contained the opposite flavor. Hamsters showed a strong preference for the test diet containing the flavor previously associated with the high-calorie diet during conditioning; however, the preference was not robust, disappearing after only 3 brief extinction trials. The learned flavor preference was specifically attributable to flavor-calorie learning and not to either flavor-flavor learning or the effects of mere exposure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dietary protein restriction and selective preference for a protein-containing diet in the golden hamster (Mesocricetus auratus)

The corrected midparental height method was introduced by Tanner in 1970 (Tanner method) and is commonly used to estimate target height in children to evaluate the effectiveness of growth-promoting therapies. It has not been established if the equation used to compute target height should be the same for children with short, normal, or tall parents. In this study, we examined the predicted target height values by parental heights in a large population-based study (n = 2402). A simple linear function of midparental height (x) was proposed to estimate target height (y): y = 45.99 + 0.78x (boys), y = 37.85+0.75x (girls), with a 95% predicted interval of about +/-10 cm. The prediction model was similar for boys and girls in SD scores (SDS), and was not affected by assortative mating or difference in parental heights. The model may underestimate the potential stature by about 2 cm for children with midparental height below -2 SDS, or 163 cm. In comparison, the Tanner method may lead to a 6-cm error in underestimating target height for these children. The function would be a better choice than the Tanner method for estimating target height in the clinical evaluation of growth promotion treatments because it is common that short children also have short parents. Children with very short parents will usually be much taller than their parents in adult stature, and we believe that a different function should be developed. The results support the proposed nondominant, non-sex-linked, polygenic inheritance in stature. The estimated heritability values were 0.75-0.78 in cm or 0.55-0.60 in SDS.     

Studies of lysophospholipids related to the hamster sperm acrosome reaction in vitro

1. One of the metabolic features of acquired immunodeficiency syndrome is increased tissue glucose uptake documented by euglycaemic-hyperinsulinaemic clamp studies, suggesting increased insulin sensitivity. However, these results may also be related to the confounding effect of increased non-insulin-mediated glucose uptake in acquired immunodeficiency syndrome, which will result in an erroneously presumed increased insulin sensitivity. To study the contribution of non-insulin-mediated glucose uptake to total tissue glucose uptake in acquired immunodeficiency syndrome, we conducted a hypoinsulinaemic clamp study in clinically stable human immunodeficiency virus-infected (Centers for Disease Control class IV) men (n = 7) and healthy subjects (n = 5). Glucose uptake was measured by a primed, continuous infusion of [3-3H]glucose in the postabsorptive state and during somatostatin-induced insulinopenia at euglycaemic (approximately 5.3 mmol/l) and hyperglycaemic (approximately 11 mmol/l) glucose concentrations. 2. Basal glucose concentration (patients, 5.2 +/- 0.1 mmol/l; control subjects, 5.3 +/- 0.1 mmol/l) and basal glucose tissue uptake (patients, 15.9 +/- 0.5 mumol min-1 kg-1 fat-free mass; control subjects, 15.2 +/- 0.4 mumol min-1 kg-1 fat-free mass) were not different between the two groups. 3. Euglycaemic glucose uptake during somatostatin infusion, reflecting non-insulin-mediated glucose uptake, decreased to 82 +/- 3% in patients and 78 +/- 2% in control subjects (not significant). Under hyperglycaemic (approximately 11 mmol/l) conditions with sustained insulinopenia, no differences in glucose uptake existed between the two groups (patients, 16.8 +/- 0.6 mumol min-1 kg-1 fat-free mass; control subjects, 16.1+/- 0.3 mumol min-1 kg-1 fat-free mass).(ABSTRACT TRUNCATED AT 250 WORDS)     

Lordosis in the male golden hamster elicited by manual stimulation: characteristics and hormonal sensitivity

The lordosis response was regularly elicited from 24 of 31 intact, adult male hamsters, using manual somatosensory stimulation of the dorsal rear body. In these males there was no correlation between measures of male-typical behavior and lordosis. Castration had no effect on male lordosis duration scores even when intromissions were eliminated. Combined treatment with estradiol benzoate and progesterone significantly increased male lordosis duration scores. The body surface was mapped with a standardized brush stimulus. For eliciting lordosis, effectiveness of stimulation increased in an almost identical manner for hormone-primed males and females from the anterior to the posterior part of the body, with the stimulation of flanks, rump, and perineum the most effective. Within each skin zone, absolute effectiveness was greater in females than in males. Various types of somato-sensory stimulation were compared for their effectiveness in eliciting lordosis. Females were more responsive to these stimuli than males, even when males were hormonally primed. These behavioral data have implications for concepts of the neural organization of male- and female-typical mating responses existing within the same individual.     

Spatial organization of facial vibrissae and cortical barrels in the guinea pig and golden hamster

The arrangements of vibrissae in guinea pigs and golden hamsters were previously reported to be different from those in mice and rats. Whereas the mystacial pads in mice and rats include four straddlers and five rows of vibrissae, guinea pigs were described to possess six rows of irregularly aligned mystacial vibrissae and no straddlers, and golden hamsters to include seven vibrissal rows and also no straddlers. We found that all of these four species possess similar vibrissal arrangements within the mystacial pad. To demonstrate this similarity, we developed a new method of sinus hair visualization in flattened and cleared preparations of the mystacial pad. Intrinsic muscles of the mystacial pad that were revealed in thick histological preparations showed clearly the structural and functional relationships between straddlers and vibrissal rows. To verify this finding, and to extend the knowledge of vibrissal cortical representations in guinea pigs and golden hamsters, we have investigated the spatial organization and the functional vibrissal representations of barrels in the posteromedial barrel subfield (PMBSF) of these rodents. The barrel morphology was clearly preserved in Nissl-stained sections and sections processed for cytochrome oxidase of flattened cerebral cortices. We demonstrate that the vibrissal arrangement in the mystacial pad is replicated in the PMBSF of guinea pigs and golden hamsters and that this arrangement is similar to that found in mice and rats. To facilitate comparative studies, these findings strongly recommend the use, in guinea pigs and golden hamsters, of the same classifications and nomenclatures that are used in mice and rats to describe mystacial vibrissae and cortical barrels.     

Rhythms of temperature selection and body temperature are out of phase in the golden hamster.

Body temperature, locomotor activity, and thermoregulatory behavior of freely moving golden hamsters maintained in a spatial thermocline were measured over several weeks. The thermoregulatory behavior of temperature selection exhibited a robust daily rhythm 180° out of phase with the rhythms of body temperature and locomotor activity. However, the parameters of the body temperature rhythm (rhythmicity, mean level, and amplitude) were not significantly affected by the thermoregulatory behavior. Although the observed phase difference between the rhythms of temperature selection and body temperature might suggest that thermoregulatory behavior is modulated to oppose (rather than to defend) the rhythm of body temperature, the absence of effect of temperature selection on the parameters of the body temperature rhythm fails to reveal the physiological significance of such opposition. Further studies are necessary to establish the physiological significance of the rhythm of temperature selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)