Cryopreservation container

Abstract

To provide a freezing storage container which has good freezing efficiency and can suppress deterioration of mobility of sperms due to freezing storage.SOLUTION: A freezing storage container 1 freezes and stores collected sperms. The freezing storage container 1 includes a cylindrical body part 2 which has a bottom part 2b and has an opened upper end 2a, a lid part 11 for blocking the opening of the body part, and a hollow projection 21 provided so as to be recessed toward the opening side from the bottom part side relative to the inner space of the body part. An apex 211 of the hollow projection is positioned in the upper half part in a height direction of the body part. For example, at a position (liquid volume V2) of the apex of the hollow projection, 70% or more of a liquid volume V1 of the body part is stored.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cryopreservation container for cryopreserving collected sperm.

Background Art

[0002] In assisted reproductive technologies (ART) such as artificial insemination of husband (AIH), in vitro fertilization (IVF), and intracytoplasmic sperm injection (ICSI), sperm is collected using a sperm collection container.

[0003] Normally, medical institutions store a patient's semen in a sperm collection container until sperm examination and predetermined procedures are performed. On the other hand, as disclosed in Patent Document 1, sperm is cryopreserved to suppress sperm deterioration and aging over a long period of time.

[0004] That is, by using a refrigerant such as liquid nitrogen to rapidly freeze the sperm contained in the cryopreservation container and storing it at an extremely low temperature, storage without time limitation becomes possible. Then, when the time comes, the entire cryopreservation container is thawed and used for fertilization and implantation in assisted reproductive medicine. The success rate of infertility treatment is affected by the motility of the sperm after thawing.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the case of a cylindrical freezing storage container with a constant internal cross-section in the longitudinal direction as disclosed in Patent Document 1, although the portion near the container wall freezes, the freezing efficiency is low, such as the central part becoming sherbet-like, and it has been found that the number of spermatozoa that can be used in reproductive medicine significantly decreases after thawing. In particular, when the diameter of the tube of the freezing storage container increases and the distance from the surface in contact with liquid nitrogen increases, the tendency of deterioration becomes stronger.

[0007] Therefore, an object of the present invention is to provide a freezing storage container having good freezing efficiency and capable of suppressing a decrease in sperm motility due to freezing storage.

Means for Solving the Problems

[0008] In order to achieve the above object, the freezing storage container of the present invention is a freezing storage container for freezing and storing collected spermatozoa, and includes a cylindrical main body portion having a bottom and an open upper end, a lid portion for closing the opening of the main body portion, and a hollow convex portion provided so as to be recessed from the bottom side toward the opening side with respect to the inner space of the main body portion.

[0009] Here, it is preferable that the top of the hollow convex portion is located in the upper half in the height direction of the main body portion. For example, at the position of the top of the hollow convex portion, 70% or more of the liquid volume of the main body portion is accommodated.

[0010] Further, the main body portion may be formed in a tapered shape toward the bottom, and the hollow convex portion may be formed in a tapered shape toward the opening of the main body portion. Furthermore, it is preferable to set the gap between the inner peripheral surface of the main body portion and the hollow convex portion to be larger than the diameter of the tip of a pipette. And it can be configured to include an annular raised portion extending downward from the bottom of the main body portion, and the lower end opening of the raised portion and the inner space of the hollow convex portion are in communication.

Effects of the Invention

[0011] The cryopreservation container of the present invention configured as described above is provided with a hollow convex portion that is recessed from the bottom side toward the upper end side with respect to the inner space of the cylindrical main body portion. That is, a refrigerant such as liquid nitrogen and the cold air generated thereby not only come into contact with the outer peripheral surface of the main body portion but also enter the inner space of the hollow convex portion, and cool the stored liquid from the center side as well.

[0012] For this reason, the freezing efficiency is good, and the entire stored liquid such as the cryopreservation solution is evenly frozen in a short time, and it is possible to suppress the decrease in sperm motility due to cryopreservation. In short, the refrigerant and cold air can be efficiently taken in from the lower end opening of the raised portion provided on the bottom side of the main body portion toward the inner space of the hollow convex portion.

[0013] Further, if the top of the hollow convex portion is located in the upper half in the height direction of the main body portion, most of the stored liquid will be cooled from the center side of the main body portion. In particular, if 70% or more of the liquid volume of the main body portion is accommodated at the top position of the hollow convex portion, it is possible to significantly suppress the decrease in sperm motility due to cryopreservation.

[0014] Furthermore, if the main body portion is formed in a tapered shape toward the bottom and the hollow convex portion is formed in a tapered shape toward the opening of the main body portion, it is easy to put the stored liquid into the main body portion, and when taking out the stored liquid, it becomes easy to insert the tip of the pipette into the gap between the main body portion and the hollow convex portion.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view for explaining the configuration of the cryopreservation container 1 of the present embodiment. FIGS. 2 and 3 are perspective views for explaining the configuration of the cryopreservation container with the lid attached and removed.

[0017] The cause of infertility can be on both the female and male sides. In the case of male infertility patients, the findings of semen examination often fall below the reference values. Examinations for men include a standard semen examination for the purpose of examining spermatogenic function, an advanced sperm function test 1 for the purpose of examining sperm function, etc. In the standard semen examination, the total motility rate is an examination item based on the WHO laboratory manual standard, and the reference value indicating normality is 40% or more. Other examination items for men include semen volume, sperm concentration, total sperm count, progressive motility rate, normal sperm morphology rate, white blood cell count, advanced sperm function test 2 (ORP test (oxidative stress level)), etc.

[0018] When the motility of sperm is low, it is diagnosed as asthenozoospermia. Asthenozoospermia means that the sperm motility rate is 40% or less and the progressive motility rate is 32% or less. The sperm motility rate of healthy men is usually 60%-80%, and it is said that the fertilization ability decreases when this motility rate decreases.

[0019] On the other hand, the collected sperm may be cryopreserved without immediately using it for assisted reproductive medicine, thawed when the opportunity arrives, and used for assisted reproductive medicine. This cryopreservation may sometimes have a long storage period, but it is preferable to suppress the deterioration and aging of sperm due to cryopreservation as much as possible.

[0020] When performing cryopreservation, the collected sperm contained in the cryopreservation container 1 is rapidly frozen using a refrigerant such as liquid nitrogen. As shown in FIG. 1, the cryopreservation container 1 of the present embodiment includes a cylindrical main body portion 2, a lid portion 11 for closing the opening 2a of the main body portion 2, and a hollow convex portion 21 provided at the center of the main body portion 2. Further, an annular raised portion 22 extending downward from the bottom portion 2b of the main body portion 2 is provided.

[0021] The main body portion 2 is formed in a cylindrical shape having a bottom portion 2b and an upper end that is open at 2a. More preferably, the main body portion 2 is formed in a shape that tapers toward the bottom portion 2b. For example, when the diameter D1 of the opening 2a is about 10 mm, the diameter D2 of the bottom portion 2b is made about 9 mm.

[0022] The lid portion 11 is attached by screwing it onto the upper end of the main body portion 2. A sealing material 12 is interposed between the upper end surface of the main body portion 2 and the lid portion 11. When the lid portion 11 is attached to close the opening 2a after accommodating the storage liquid in the opening 2a of the main body portion 2 provided with a screw groove at the upper end as shown in FIG. 3, a state in which cryopreservation is possible as shown in FIG. 2 is achieved.

[0023] Then, in the cryopreservation container 1 of the present embodiment, a hollow convex portion 21 is provided so as to be recessed from the bottom portion 2b side toward the opening 2a side with respect to the inner space of the main body portion 2. The inner space of the hollow convex portion 21 communicates with the lower end opening of the raised portion 22 as shown in FIG. 1. That is, the outer peripheral surface of the main body portion 2 and the central (axis) side can be brought into contact with a refrigerant such as liquid nitrogen or air (cold air) in a state where the temperature and the like are the same.

[0024] The hollow convex portion 21 formed so as to bulge from the bottom portion 2b side toward the opening 2a is preferably formed in a conical shape that tapers toward the opening 2a of the main body portion 2. That is, the diameter D3 of the top portion 211 of the hollow convex portion 21 is made smaller than the diameter D4 on the bottom portion 2b side of the hollow convex portion 21.

[0025] In the main body 2 of this cryopreservation container 1, a cryopreservation solution mixed with sperm is stored as the storage liquid. That is, the storage liquid is filled in the annular gap in the cross-section between the inner peripheral surface of the main body 2 and the hollow convex portion 21 from the bottom 2b of the main body 2, and above the top 211 of the hollow convex portion 21, it is filled in the circular inner cavity of the main body 2.

[0026] For example, the main body 2 and the hollow convex portion 21 with a wall thickness of 0.6 mm are formed, where the diameter D1 of the upper end (opening 2a) is 10.4 mm, the diameter D2 of the bottom 2b is 9.3 mm, and the height H1 including the raised portion 22 with a height H2 of 2.0 mm is 28.0 mm. The liquid volume V1 at the upper end of this main body 2 is 1.0 cc, and the liquid volume V2 at the position of the top 211 of the hollow convex portion 21 is 0.7 cc. That is, at the position of the top 211 of the hollow convex portion 21, about 70% or more than 70% of the liquid volume V1 of the main body 2 can be stored.

[0027] On the cryopreservation container 1, a label portion 13 as shown in FIG. 2 is provided to prevent misidentification of the specimen. Information such as patient identification information and collection date is given to the label portion 13 by printing, sealing, etc.

[0028] Next, the usage method of the cryopreservation container 1 of this embodiment will be described step by step from sperm collection. As shown in FIG. 4, the sperm collection container 3 includes a container body 32 having a storage portion 31 for storing sperm S, and an inner lid 33 for making the storage portion 31 a sealed space after sperm collection.

[0029] The container body 32 is integrally formed with a conical inner container 321 for storing sperm S and a cylindrical outer container 322 covering the periphery of the inner container 321. Since the upper input port of the inner container 321 expands in a funnel shape, sperm collection is easy to perform.

[0030] On the other hand, the inner lid 33 is also molded into a frustum cone shape by polypropylene. The inner peripheral surface of the tapered portion (frustum cone-shaped portion) of the inner container 321 and the outer peripheral surface of the inner lid 33 have substantially the same shape, and the inclination angle of the tapered portion with respect to the axis of the container body 32 can be set to about 10° to 30°.

[0031] The storage part 31 corresponds to the space surrounded by the lower part of the inner container 321 and the bottom surface of the inner lid 33. That is, on the frustum-shaped inner peripheral surface above the storage part 31 formed in a cylindrical shape in the inner container 321, the outer peripheral surface of the inner lid 33 is in close contact, and the bottom surface of the inner lid 33 serves as the ceiling surface of the storage part 31 (see Fig. 5).

[0032] Here, since the amount of sperm (semen) collected at one time is about 3 cc - 10 cc, the volume of the storage part 31 may be formed to be slightly larger than 10 cc. Also, the inner peripheral surface of the inner container 321 and the inner surface of the storage part 31 are mirror-finished so that semen does not easily adhere to the wall surface and easily flows down. If the container body 32 is transparent or translucent, the patient can easily visually confirm that the sperm S is stored in the storage part 31 and the amount of semen collected.

[0033] Then, in order to reduce the volume of the inner container 321, a gripping part 331 having a thread groove that meshes with the thread groove provided on the upper edge of the container body 32 is provided on the upper edge of the inner lid 33 inserted into the inner container 321. After semen collection, the patient quickly fits the inner lid 33 with the upper lid attached into the container body 32 and screws it in to firmly fix the inner lid 33 to the container body 32. By doing so, the sperm S after semen collection does not come into contact with air, and deterioration of the sperm S due to oxidation can be suppressed.

[0034] That is, when the thread groove of this gripping part 331 is screwed into the thread groove of the container body 32, the inner lid 33 is firmly fixed to the container body 32, and the sperm S enclosed in the space surrounded by the bottomed cylindrical storage part 31 and the bottom surface of the inner lid 33 is transported to the medical institution without coming into contact with air or leaking.

[0035] FIG. 5 is an explanatory diagram showing the situation of the procedure for collecting sperm S from the sperm collection container 3. At the center of the bottom of the inner container 321 serving as the storage part 31, a collection part 311 is provided. The collection part 311 is a circular thin part formed so as to be easily pierced by the needle 51 (cannula) of the syringe 5 for collecting sperm S. The collection part 311 is formed to be thinner than the surrounding part, for example, about 1 mm in diameter and about 0.1 mm in thickness.

[0036] Therefore, the needle 51 of the syringe 5 is inserted into the collection part 311 of the storage part 31, and the sperm S contained in the storage part 31 is collected into the syringe 5. At this time, since the inner lid 33 can remain fitted, contact between the sperm S and the outside air can be avoided, and oxidation of the sperm S and intrusion of dust and the like can be prevented.

[0037] The sperm S collected by the syringe 5 is transferred to a Spitz tube and then subjected to a washing process. Subsequently, good-quality sperm S is selected and collected using a sperm preparation method such as concentration by centrifugation or the swim-up method. In addition, the treatment for these collected sperm S can also be performed after thawing after cryopreservation.

[0038] The collected good-quality sperm S is mixed with a cryopreservation solution. In short, in order to prevent the crystallized moisture from damaging the sperm S, it is mixed with a sperm cryopreservation medium (Sperm Freezing medium).

[0039] In this way, the sperm-containing liquid in which the cryopreservation solution and the sperm S are mixed becomes the liquid to be contained in the cryopreservation container 1 of the present embodiment. The liquid to be contained is injected through the opening 2a of the main body 2 with the lid 11 removed as shown in FIG. 3 using a pipette 4 (see FIG. 7) or the like.

[0040] The injection into the main body 2 can also be performed by separately injecting the sperm S and the cryopreservation solution and mixing them inside the main body 2. In the main body 2, a liquid to be contained of 0.7 cc to 1.0 cc is contained with reference to the position of the top 211. After containment, the opening 2a of the main body 2 is closed by screwing in the lid 11 (see FIG. 2).

[0041] On the label portion 13 on the side surface of the main body portion 2, identification information such as the patient's name and identification number, and information such as the collection date are entered before the injection of the stored liquid or after the lid portion 11 is attached. This can prevent misidentification of the specimens. Since the label portion 13 is provided by utilizing the wide outer peripheral surface of the main body portion 2, a lot of information can be entered.

[0042] The freezing of the cryopreservation containers 1 can be performed simultaneously for a plurality of them. For example, as shown in FIG. 6, six cryopreservation containers 1 can be set on one freezing cane 6 and the processing for freezing can be performed.

[0043] When performing the freezing process, it is not preferable to directly put the cane 6 with the cryopreservation container 1 set therein into a nitrogen tank at -196°C for freezing. Instead, it is preferable to cool it gradually. FIG. 6 is a diagram schematically showing the cooling process by the gas phase of the liquid nitrogen 71.

[0044] For example, a refrigerant such as liquid nitrogen 71 is stored in a storage box 7 made of styrofoam or the like, and the cryopreservation container 1 attached to the cane 6 is applied to the cold air of about 2°C to 5°C of the liquid nitrogen 71 rising therefrom, thereby gradually cooling the stored liquid containing the sperm S. By doing so, the damage to the sperm S due to freezing can be reduced.

[0045] During this cooling, not only the outer peripheral surface of the main body portion 2 is cooled by the cold air, but also the cold air enters the inner cavity of the conical hollow convex portion 21 provided at the center, and the stored liquid can be efficiently cooled.

[0046] Note that FIG. 6 is only an image diagram and does not show the actual treatment method. For example, when simple freezing starts due to cooling, the cane 6 should be oriented so that the lid portion 11 is on top, and it is necessary to freeze in a state where the stored liquid has accumulated from the bottom 2b.

[0047] The cryopreservation container 1 that has been subjected to the cooling treatment by the gas phase of liquid nitrogen 71 is put into and stored in a nitrogen tank with a lid (not shown) in which liquid nitrogen at -196°C is stored, while being attached to the cane 6 for cryopreservation.

[0048] Also at this time, not only the outer peripheral surface of the main body 2 but also the inner cavity of the conical hollow convex portion 21 provided at the center is filled with liquid nitrogen, and the stored liquid will be frozen efficiently and evenly. At an extremely low temperature of -196°C, the sperm S does not deteriorate or age, so there is no time limit for cryopreservation.

[0049] When the time comes to use the cryopreserved sperm S for assisted reproductive medicine, select the corresponding cryopreservation container 1 from the nitrogen tank based on the information printed on the label portion 13, take it out, immerse it in warm water at about 30°C to 35°C, and thaw it while shaking.

[0050] After thawing the stored liquid in the cryopreservation container 1 in this way, remove the lid portion 11, and as shown in FIG. 7, insert the tip of the pipette 4 into the main body 2, and collect the stored liquid containing the sperm S by sucking it up.

[0051] The main body 2 of the cryopreservation container 1 has a shape that tapers towards the bottom 2b, but the hollow convex portion 21 has a shape that tapers towards the opening 2a of the main body 2. Therefore, a gap through which the tip of the pipette 4 used for collecting the stored sperm S can pass is secured between the inner peripheral surface of the main body 2 and the hollow convex portion 21. For example, the main body 2 and the hollow convex portion 21 are manufactured so as to have a gap of about 3 mm to 4 mm.

[0052] Therefore, the tip of the pipette 4 can reach the bottom 2b of the main body 2, and all of the stored liquid can be sucked up. The stored liquid containing the sucked-up sperm S is transferred to a Spitz tube and used for assisted reproductive medicine (ART) such as artificial insemination by husband (AIH), in vitro fertilization (IVF), and intracytoplasmic sperm injection (ICSI).

[0053] Next, an experiment conducted to confirm the effects on sperm S cryopreserved by the cryopreservation container 1 of the present embodiment will be described. In the experiment, changes in the sperm motility rate (%) of sperm S before and after thawing were examined.

[0054] In addition, in order to confirm the effects of the cryopreservation container 1 (Example 1) of the present embodiment, an experiment using a comparative example was also conducted. The container used as the comparative example is a conventionally used cylindrical storage container, which is a cylindrical container with a constant thickness (diameter) and has no configuration corresponding to the hollow convex portion 21 of the cryopreservation container 1 of the present embodiment. Specifically, a cylindrical container with a height of 29.0 mm, a diameter of 12.0 mm, and a liquid volume of 1.2 cc was used.

[0055] On the other hand, the cryopreservation container 1 used as Example 1, as described with reference to FIG. 1, has a height H1 of 28.0 mm, an upper end diameter D1 of 10.4 mm, a bottom 2b diameter D2 of 9.3 mm, and a wall thickness of 0.6 mm. The liquid volume V1 of the main body 2 is 1.0 cc at the upper end, but in the experiment, it was used within the range where the liquid volume V2 at the position of the top 211 of the hollow convex portion 21 is 0.7 cc.

[0056] Five specimens (A - E) were used in the experiment. The sperm motility rates of the specimens (A - E) before freezing were from 58.7% to 68.5%. These specimens (A - E) were respectively injected into the cryopreservation container 1 of Example 1 and the storage container of the comparative example, subjected to the freezing treatment as described above, cryopreserved in a nitrogen tank for a certain period, and then taken out and thawed.

[0057] As a result, the sperm motility rates of sperm S cryopreserved in the cryopreservation container 1 of Example 1 were from 56.4% to 63.0%. On the other hand, the sperm motility rates of sperm S cryopreserved in the storage container of the comparative example were from 29.4% to 41.1%. FIG. 8 is a bar graph showing the change in sperm motility rate due to this cryopreservation as a change rate.

[0058] As can be seen from looking at this bar graph, it can be understood that the sperm motility rate of sperm S cryopreserved in the cryopreservation container 1 of Example 1 has hardly changed compared to before and after cryopreservation. Specifically, the change rate is within the range of 92.0% to 96.0%, and it can be understood that the decrease in sperm motility rate due to cryopreservation is suppressed to 10% or less.

[0059] In contrast, it can be seen that the sperm motility rate of sperm S cryopreserved in the storage container of the comparative example has been halved compared to before and after cryopreservation. Specifically, the change rate is in the range of 51.0% to 60.0%, and for any of the specimens (A - E), a significant decrease in sperm motility rate is observed.

[0060] As described above, it is considered that sperm S does not deteriorate while being cryopreserved in an ultra - low - temperature nitrogen tank. Therefore, as the cause of such results, it can be presumed that there are differences in the changes in the state until freezing.

[0061] That is, since the cryopreservation container 1 of Example 1 has the hollow convex portion 21, it can be presumed that the entire storage liquid accommodated in the main body portion 2 is efficiently and evenly frozen, suppressing the deterioration of sperm S at the stage until freezing.

[0062] In contrast, when the storage container of the comparative example is used, the freezing of the central part is slower than the part adjacent to the outer peripheral surface of the storage container, and the time in a sherbet - like state becomes longer. Therefore, it can be presumed that the deterioration of sperm S progresses during that time. As a result, the significant reduction in the number of sperm that can be used for reproductive medicine after thawing is as described in the above - mentioned background art.

[0063] Next, the operation of the cryopreservation container 1 of this embodiment will be described. The cryopreservation container 1 of the present embodiment configured as described above is provided with a hollow convex portion 21 that is recessed from the bottom 2b side toward the upper end opening 2a side with respect to the inner cavity of the cylindrical main body portion 2. That is, a refrigerant such as liquid nitrogen and the cold air generated thereby not only come into contact with the outer peripheral surface of the main body portion 2, but also enter the inner cavity of the hollow convex portion 21, and cool the liquid to be stored from the center side as well.

[0064] For this reason, the freezing efficiency is good, and the entire liquid to be stored such as the cryopreservation solution is evenly frozen in a short time, and it is possible to suppress the decrease in sperm motility due to cryopreservation. In short, the refrigerant and cold air can be efficiently taken in from the lower end opening of the raised portion 22 provided on the bottom 2b side of the main body portion 2 toward the inner cavity of the hollow convex portion 21.

[0065] Also, if the position of the top portion 211 of the hollow convex portion 21 is located in the upper half in the height direction of the main body portion 2, most of the liquid to be stored will be cooled from the center side of the main body portion 2. In particular, if about 70% or more of the liquid volume V1 of the main body portion 2 is accommodated at the position of the top portion 211 of the hollow convex portion 21, it is possible to significantly suppress the decrease in sperm motility due to cryopreservation.

[0066] Furthermore, if the main body portion 2 is formed in a tapered shape toward the bottom 2b and the hollow convex portion 21 is formed in a tapered shape toward the opening 2a of the main body portion 2, it is easy to put the liquid to be stored into the main body portion 2, and when taking out the liquid to be stored, it becomes easy to insert the tip of the pipette 4 into the gap between the main body portion 2 and the hollow convex portion 21. As a result, the entire amount of the liquid to be stored can be easily sucked up.

[0067] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes that do not deviate from the gist of the present invention are included in the present invention.

[0068] For example, in the above-described embodiment, the main body portion 2 having a tapered shape toward the bottom portion 2b was described, but the present invention is not limited thereto, and the main body portion may have a constant thickness (diameter) in the height direction. Also, the hollow convex portion 21 may have a constant thickness (diameter) in the height direction.

Explanation of Reference Numerals

[0069] 1: Cryopreservation container 11: Lid portion 13: Label portion 2: Main body portion 2a: Opening 2b: Bottom portion 21: Hollow convex portion 211: Top portion 22: Raised platform portion 4: Pipette S: Sperm V1: (Liquid volume of the main body portion) V2: (Liquid volume at the position of the top portion)

Claims

1. A cryopreservation container for cryopreserving collected sperm, comprising: a cylindrical main body having a bottom and an open upper end; a lid for closing the opening of the main body; a hollow convex portion provided so as to be recessed from the bottom side toward the opening side with respect to the inner space of the main body; the top of the hollow convex portion is located in the upper half in the height direction of the main body, and a circular cross-sectional inner space is formed between the top and the opening; the main body is formed in a tapered shape toward the bottom, and the hollow convex portion is formed in a tapered shape toward the opening of the main body, and a cryopreservation container, wherein a gap between the inner peripheral surface of the main body and the hollow convex portion is larger than the diameter of the tip of a pipette.

2. The cryopreservation container according to claim 1, wherein at least 70% of the liquid volume of the main body is accommodated at the position of the top of the hollow convex portion.

3. The cryopreservation container according to claim 1 or 2, further comprising an annular raised portion extending downward from the bottom of the main body, wherein a lower end opening of the raised portion communicates with the inner space of the hollow convex portion.

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